ah practical photography master 2012.pdf

8/20/2019 AH Practical Photography Master 2012.pdf

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Contents

Introduction …………………………………………………….. 1Why Dental Photography ………………………………………. 1

What is Photography …………………………………………… 2

Light Properties ………………………………………………… 3Basic Colors ……………………………………………………. 4

Basic Tools …………………………………………………….. 6Camera ………………………………………………….. 6

Lenses …………………………………………………… 8Minimal Allowed Distance (MAD) …………………….. 9

Light Source …………………………………………….. 12

Assisting Tools …………………………………………………. 14Retractors ……………………………………………….. 14

Photographic mirrors …………………………………… 14

Backgrounds …………………………………………… 16Optical Image Quality ………………………………………… 17

Sharpness ………………………………………………. 18

Depth of field ………………………………………….. 18

Brightness ……………………………………………… 20Contrast ………………………………………………… 21

Factors Affecting Light Exposure …..................... 21

Color Balance ………………………………………….. 24Technical Image Quality ……………………………………… 25

Magnification ………………………………………….. 25

Working Distance ……………………………………… 26Camera-object relation …………………….................... 27

Digital Photography ………………………………………….. 30Which Digital Camera ……………………………………….. 31

Comparison between digital and analogue photography ……. 34

Different Camera Modes ………………………….................. 34

Errors and Solutions …………………………………………. 35

Recent a pplication of photography ………………................... 39Copying photographs ……………………………................... 40

Copying radiographs ………………………………………… 40Archiving recorded image …………………………………… 42

Required shots for different dental specialties 44

Definitions …………………………………………………… 45Photographic hints …………………………………………… 47


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Introduction

Registration of past man activities and knowledge enabled us to know a lotabout previous ancient civilizations and will allow future generations to

know about us. Drawing was the only way for visual registration in theancient civilizations, but it was replaced gradually by photography as its

more easily saved, reproduced and shared.

It was claimed that “one picture worse more than 1000 words”, so,

visual media now are so impressing and effective in not only registration,

but also in decision making and taking. Lot of activity fields are photography-dependant for various purposes. The medical field isn’t an

exception of this, and particularly dentistry as it deals mostly with visualaspects of the personal representation. Medical photography is a science

dealing with producing high standard photographs to record the medical procedures for a variety of purposes.

Photography term comes from the two Greek words: “photos” which

means light and “graphos” which means drawing”.

Why Dental Photography/?

As a general rule, any invasive and/or irreversible procedure should be

registered and recorded before starting the procedure by photographs.

Two main aspects dictate using photographs in the dental field:

1- Legal aspect: for the dentist to protect him (her) self if the patientclaims an error occurred or there was a technical mistake made by the

dentist. The only proof to deny or prove this; is preoperative recordingincluding photographs. Patient may not be satisfied of the dental

treatment as the patient can not remember the preoperative conditions

(shape, esthetics, morphology,……..), but presence of preoperative

recoding will help understanding the condition. Another legal point isthe ownership and copyright of the produced image.

2- Medical aspect: which may include the following purposes:a. Documentation

i.

Diagnosis (Fig 1-a)


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ii.

Follow up (Fig 1-b)

iii. Contribution to building data baseiv.

Illustration (educational and research purposes).

(a) (b)

Fig (1): (a) diagnosis, (b) follow up.

b.

Communication

i.

With patients (patient education).ii. With colleagues (for presentations, knowledge sharing).

iii.

Consultation (now through the internet video conference,

we can make remote consultation)

c. Marketing and skill developmenti.

For personal presentations of available services in the

dental care clinics, equipments, facilities, …….. ii.

To evaluate self skill development and future

enhancements.

What is Photography?Photography is simply a simulation of the human vision process, the

camera system is an imitation of the visual apparatus including lens, image

receptor (retina of the eye, photographic film, or digital receptor) (Fig 2).

(a) (b)Fig (2): Cross section of the human eye (a) and in camera (b)


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So, photography is the process through which we can record an imagefor a certain object on light sensitive receptor, processing data, record it, and

retrieve it when needed. To understand concepts of photography, some light

properties should be known as photography is receiving the light reflectedfrom any object.

Some light properties

1- Light is composed of seven colors with different wave lengthsforming the visible light spectrum (fig. 3). (Basic and complementary

colors will be explained later)

Fig (3): The light spectrum

2-

The object’s color depends on its ability absorb the whole spectrum

except one (or a combination) of a certain wave length producing theobject’s color.

3-

Light travels in straight lines

4-

Reflection: light is completely reflected when strikes a reflective

surface (a mirror). As shown in figure 5, the reflected image on themirror is inversed (horizontally) (a), and that the angle of incidence

equals the angle of reflection (b). (applied in intraoral photography)


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(a) (b)

Fig (5): The reflected image on a mirror (a), and relation between incident and reflected ray (b).

5-

Deflection: which means deviation of the light from its straight coursedue to passing through two different media (air and water or air and

glass) (fig 6). This phenomenon is the base on which a lens can collect

light beam when passing from air to glass of the lens at a certain point.

(a) (b)Fig (6): The deflection property when light passes through two different media, air and water (a),

and air and glass (b)

What are the basic colors?

There has been an old debate about basic colors. People working in art fieldconsidered a basic color is that color that can not be obtained from other

colors, so they considered basic colors are Red , Blue and Yellow . Therewere several objections to this hypothesis as:

A- It was found that those colors can be obtained from mix of certainshades of other colors.


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B-

This hypothesis could not explain the relation between basic and

complementary colors (will be explained later).On the other hand scientists considered the basic colors are: Red , Blue andGreen (not yellow). They have 2 basic facts according to which they

claimed the basic colors:The fir st is that the receptors in the retina in the human eye can only see red,

blue and green colors (with unlimited combinations).Additionally , practical application of considering a green color as one of the

basic colors is that balance between basic and complementary colors.Simply, each basic color when added to other specific complementary color

will result in obtaining gray color (which is the mid-shade between black

and white which are considered neutral colors).

Principal Red Blue Green

+ + +Complementary Cyan Yellow Magenta

= = =

Balanced Shade Gray Gray Gray

NB: Obtaining pure gray color in the image means all other colors are balanced to natural colors as in real (which has important indication in

image interpretation).

The second fact is an optic phenomenon; mixing the three basic colors inequal proportions and received on a black board will produce a white spot

(Fig 4A) and mixing complementary colors in equal proportions andreceived on a white board will produce black spot (Fig 4B) (which will not

happen if the yellow color is considered a basic color). (Note that

combination of such colors will produce the two neutral colors, white

[mixing basic colors] and black [mixing complementary colors])


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A BFig 4: “A” mixing basic colors gives white spot, while in “B” mixing complementarycolors produce black spot.

Needed tools

For production of high quality dental images, special tools are needed toachieve such goal. Two types of tools are needed:

I- Basic (principle) tools:A) Camera (optical or digital)

B) Special accessories including lens, close up tools (extensiontubes or close up lenses).

C) Light Source (natural, artificial, continuous or snap)

II-

Assisting tools, including cheek and lip retractors, photographicmirrors and photographic background.

I- Basic (principle) tools

A) Camera:

i. Viewfi nder cameras : which are not suitable for dental photography which,as it can not produce the required magnification because its lens is fixed to

the camera body and can not be changed (Fig 5, left) and its responsible for

what is know as parallax (Fig 5, right).

What is parallax?

It’s the difference between what the eye can see through the viewfinder lens

and what the film will record through the camera lens. This phenomenon ismore noticed in close up photography (Fig 6).


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Fig (5): Range finder camera (left), and parallax phenomenon (right).

ii. SLR cameras: which represents the Single Lens R eflex technique, wherethe lens is interchangeable according to the required assignment (Fig 6,left).The right figure shows a cross section in the SLR cameras explaining how

the image is transferred to the view finder through one lens which isinterchangeable through a pentaprism on the top of the camera body.

Fig (6): SLR camera (left) and schematic diagram (right).1) The lens2) Reflecting mirror (45° on the horizontal plane)

3) Sutter screen (when opens, its exposes the film to the light passing through the lens). Thespeed of the shutter screen to open and close (shutter speed) controls the amount of light


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strikes the film in combination with the lens aperture (when using a continuous lightsource), which be discussed later

4) Film5) Condenser6) Condenser (intensifies light beam to pentaprism)7) Pentaprism (reflecting light to the view finder).

8)

View finder eye piece (can see precisely what the film is going to record).

When the release button is pushed, the reflecting mirror turns upward, the

shutter screen is opened and the film is exposed to light.

B. Special accessories

i . L enses

A lens is a special apparatus that collects light beam in a specific pointto form a sharp image in a certain area called focus point.

Focus: is the point at which the sharpest image of an object is formed.

Focal length: is the distance between the center of the lens and the focus

point when the lens is set at infinity (dotted arrow) (Fig 7).

A: the object A”: the object’s image at the focus

Fig (7): The proper focusing of the object (A) in the focus point (A”) (left) and when the object(B) in the wrong focus (B”) (right). “CC” denoting the circle of confusion which is thedifference between the supposed focal point and virtual focus at (B”) resulting in blurred

image.

If the object moves from point A to point B (right side of the figure), and the

position of the lens and the film are fixed, the sharpest image of the object in position “B” is formed at the point B” behind the focal point. The image

formed at the film plane will be blurred (pre-focus image). The “cc” is animaginary circle known as the circle of confusion which represents the

difference between the actual image position and the proposed sharpestimage position. Increasing the difference between two positions will

increase the circle of confusion, leads to more blurred image.


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Minimal Allowed Distance (MAD):

It is the minimum distance at which a lens can form a sharp image atthe focus point. Getting closer to the object beyond this limit will produce a

blurred image. This distance is recorded on the lens body and it differs from

one focal length of the lens to another. This distance is greater by increasingthe focal length of the lens, e.g the focal length of a lens is 50 mm and the

minimal allowed distance is 40 cm, in a lens with 100 mm focal length, theminimal allowed distance will be 65 cm, i.e if we use a lens with a focal

length 100 mm, we can not get closer than 65 cm (Fig 8) unless we useadditional accessories (a lens with macro option or adding close up lens to

the original lens).

Fig (8): Minimal allowed distance of lenses with different focal lengths.

As the visible light spectrum contains seven colors with different wavelengths; each wave length has a different deflecting angle when passing

though the lens producing different focus points for each wave length whichis known as aberration .

Aberration : is defined as the failure of a lens to bring all the wave lengths ofa light beam to an exact same focus (Fig 9).


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Fig (9): Red wave length has a different focusing point than blue one.

Introducing the achromatic lens solved this problem partially as this lensconsisting of two or more elements, usually made of crown glass and flint

glass. This lens has been corrected for aberration in that it has the same focal

point with respect to two different colors (red and blue) (Fig 9A).

Apochromatic lens , similar to the achromatic lens, this lens corrects for

three colors (red, blue and green) (Fig 9B), greatly reducing the blur caused by the colors uncorrected by the achromatic lens. That’s why lens prices

vary greatly according to its ability of aberration correction.

Fig (9A): Achromatic lens with a coat to correct blue wave length deviation

Fig (9B): Apochromatic lens with 2 coats tocorrect blue and green wave length deviation

Types of lenses (according to the focal length)

Camera lenses are classified according to its focal length into:a-

Standard lens: which its focal length is between 45-55 mm (which has

the same angle of vision of the human eye).

b-

Wide Angle lens: where the focal length is less than 45 mm.

c- Telephoto lenses: where the focal length is larger than 55 mm.


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d-

Zoom lens: with more than one focal length in the same body. Those

lenses may be either wide-wide, wide-standard, standard-telephoto,telephoto-telephoto or wide-telephoto zoom lenses.

The smaller the focal length (wide angle lens) (left side), the smaller the

object size (the larger the angle of view) and vice versa (Fig 10).

Fig (10): The effect of focal length of the lens on the object size, wide angle lens (left), and

telephoto lens (right).

The camera lens has 2 calibrations, one for the distance adjustments (in the

manual distance adjustment cameras), and the other for aperture adjustments.The aperture of the lens is the diameter of the opening that permits light to

pass through it to the film when the shutter screen opens. Its calibrationstarts from 1.4 (sometimes 1.2), 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32 and is

represented as f/number or f-stop. This f-stop is calculated by dividing the

focal length of the lens by the diameter of the opening. If the shutter speedand light conditions are constant, one f-stop gives half the amount of light

the previous f-stop gives (f/8 gives half the light f/5.6 gives), while it gives

double the light amount the next f-stop gives (f/8 gives double light the f/16gives), so the bigger the number, the lesser the light allowed to passes to the

film (Fig 11).

Fig (11): Range of f-stop in a standard lens


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The aperture value controls the amount of light strikes the film in

combination with the shutter speed (when using continuous light) and incombination with the object-lens distance and flash guide number (when

using snap light), assuming the film sensitivity is constant. The number

written in the following formula 1:1.4, f = 55mm, means that the maximumaperture of this lens is 1.4 while its focal length is 55mm. Zoom lenses may

have two number indicating the maximum aperture (the smaller numberindicates the maximum aperture at the smaller focal length and the other

indicating the maximum aperture at the larger focal length) as follows: 1:2.8~4 f = 35~85mm. This means that the focal length of this zoom lens

ranges from 35 mm (wide) to 85 mm (tele) and the maximum aperture at 35

mm = 2.8 while at 85 mm = 4 (Fig 12).

Fig (12): Data on the lens identifying maximum aperture and focal length

2. Light Source

Light source is one of the most important factors affecting the image quality

as it may affect brightness, contrast and hue of the image.

Light sources are classified according to either its nature or duration.

I) According to nature:i) Natural light: which include the day light exposure, whether director indirect (shaded areas) (Fig 13 left)

ii) Artificial light: which may be tungsten or florescent light source,

(Fig 13 right).


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Fig (13): Natural (day) light (left) artificial (right)

II) According to duration:

i) Continuous light which is either natural or artificial

ii) Snap light: flash light. Flashes may be mounted in a top or side position (Fig 14, left), but this gives an ugly shadow to the obtained image

(Fig 14 right). The ring flash which is mounted on the lens (Fig 15 left) will produce shadowless image by equalizing amount of light from all directions

(Fig 15 right). It’s very useful in close up and dental photography.

Fig (14): Top position flash unit (left), and resulted ugly shadow (right)

Fig (15): Ring flash unit (left), and shadowless image (right).


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Assisting tools:

1)

Retractors: using cheek and lip retractors expose the intra-oral

target area clearly to be photographed (fig 16 a, b and c). Plastic

retractors (c) are superior to metal ones (d) to avoid lightreflection.

NB: Metal retractors were used in the past as they could be sterilized andautoclaved but recently plastic retractors are made of autoclavable materials.

a b

c dFig (16): Semi-circular self-retained plastic retractor is useful (a, b and c), while metal

retractor may create unaccepted reflection that may affect final image.

2)

Photographic mirrors: specially designed mirrors to assist photographing certain areas that are not clearly photographeddirectly. They are either metal or glass mirrors. Glass mirrors

being cheaper, but sometimes it produces what is known asghost image (second image), as two surfaces are reflecting the

image, the silver coating of the glass (rear surfaced mirror), andthe glass surface itself which partially reflects the image (fig 17


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left and fig 18). In addition to be cheaper, glass mirrors can be

precisely customized with different sizes as needed by eachoperator. Metal mirrors on the other hand, gives a single

reflection as only one surface will reflect the image (front-

surfaced mirror, fig 17, right) it’s durable, easy sterilized,thinner (will not annoy the patient).

GI = ghost image PI = Primary imageFig (17): Primary and ghost images in glass and metal mirrors.

Fig (18): Intraoral occlusal photograph of maxillary dental implant with ghost image of

the implant (arrow)

Occlusal and lateral mir rors:

Occlusal mirrors are trapezoid in shape, used for photography of occlusal

surfaces of upper and/or lower arches (fig 19), while lateral mirrors arenearly rectangular in shape and are useful for photography of side views of

the teeth (opened or in occlusion) (fig 20), and also may be useful for lingual photography. The mirror (occlusal or lateral) should be placed 45° (fig 19,

20), to both the object (to obtain proper viewing of the object) and camera toavoid reflection. It should be noted that mirror image is reversed


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(horizontally), i.e. the right side appears as left and vice versa (this can be

easily corrected now by photo editing software).

(A) (B) (C)

(A) (B) (C)

Fig (19): Intraoral mirror(occlusal mirror above, side lateral mirror, below): (A)schematic diagram for 45° angle, (B) clinical view and (C) the resulted image.

Perfect presentation of certain clinical situations can only be achieved by

using intraoral photographic mirrors (Fig 20).

Fig (20): showing lateral (side view of maxilla teeth), left direct (without the mirror),

right using intraoral mirror showing perfect presentation of the available space for the

implant and good evaluation of the neighboring teeth alignment.

3)

Background: it’s the surface behind the object to be

photographed, it should fulfill 4 main criteria:-

Suitable color for the object (sufficient contrast).

- Being non reflective.-

Composed only of one color.


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-

Flat with no texture.

Any failure to choose the proper background may affect the optical quality

of the image or would disturb the person who watches it (Fig 21).

(A) Bad background color (wrong) (B) Multiple background color (wrong)

(C) Reflective background (wrong) (D) Proper Background

Fig (21): Effect of background on the image quality.

Image quality:

The photographed image in the dental field (as well as all fields) should

fulfill certain quality criteria to be accepted

A) Optical image quality.B) Technical image quality (photographic conditions and photographer

performance).

A) Optical image quality includes the application of optical basic concepts to

produced images with high quality. This includes:

- Sharpness.

- Sufficient depth of field (depth of focus).- Brightness and contrast.

- Color balance (hue).


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- Sharpness:

As previously mentioned a sharp image means formation of the object’s

image through the lens in the focal point, and a sharp image means that theimage components are sharply defined from each other and that a point or a

line in the object is represented by a point or a line in the image (fig 22).Precise adjustment of the distance scale permits a sharp image quality.

Although in modern and advanced camera systems, the distance isautomatically adjusted through the auto-focus mechanism, working within

camera limits will ensure the sharpness.

Fig (22): Blurred image (left) (unaccepted) and sharp image (right).

- Depth of f ield (depth of f ocus):

Is the portion of the scene that is in focus or it is the area in which all objects,located at different distances from the camera, appear in focus (Fig 23).

Fig (23): Effect of depth of field (focus) on image quality.


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Four factors may influence the degree of depth of field (DOF):

(a) The focal length of the lens.

(b) The distance of the object from the lens.(c) The aperture and

(d) Focal plane (plane at which the distance scale is adjusted).Additional factor may be the distance between elements in the foreground

and elements in the background of the frame.

1- The bigger the focal length of the lens (telephoto lenses), the narrower the

DOF, and similarly, the closer the object (close up or macro photography),the narrower the DOF.

2- The smaller the aperture, the bigger the DOF (fig 24).

Fig (24): Effect of aperture on DOF (left), and distance between objects close and far

from the camera (right).

3- Focal Plane: as an optical phenomenon, 1/3 of the area to be photographed in front of, and 2/3 behind the focal plane lie in the

focus area (fig 25). So, when photographing frontal view of occlusion,

if the focal plane is adjusted at the level of central incisor, an area in

front of this focal plane will lie in focus, although there is no object to be photographed occupying this area, while the area behind this plane

will not extend to include the first molar which is needed to be insharp focus (gray area, left image). Readjusting the focal plane to be

at the level of the canine or first premolar will help including the areasin front and behind this plane in a sharp focus (right image, gray area).

So in dental photography we need to capture images for small objects so wehave to use telephoto lenses with close up (macrophotography) which


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greatly decreases the depth of focus. This can be compensated by using

small lens aperture and shift the focal plane slightly posterior (Fig 25).

Fig (25): Effect of position of focal plane on depth of field (gray area).

- Br ightness and contrast: affected by proper light exposure and processing

of the film respectively.

- Br ightness

It’s the amount of light being reflected off a subject or surface, and

representing the lightness value from black {0} to white {255} (Fig 26).

0 255Fig (26): The brightness scale from 0-255 (applied in color and black and white mode).

Proper film exposure will result in a well illuminated image, whileincreasing film exposure results in a more bright image (all color tones are

more bight). On the other hand, decreasing the film exposure will producedarker image (Fig 27, left middle and right respectively). In other words,

increasing brightness of an image means increasing certain amount of light

to all image components and dark image means decreasing certain amount of

light to all image components.


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Normal Lighter Darker

Fig (27): Different grades of image brightness.

- Contrast

Contrast in general is the ability to distinguish differences. In photographic

field it can be defined as the difference between the dark and light areas in a

photo. The greater the difference, the higher the contrast (Fig 28). The brightareas become brighter and the dark areas become darker.

Normal contrast High Low

Fig (28): Different grades of image contrast.

Brightness and contrast can be adjusted by photo-editing software within

limits

NB Brightness is related on film exposure to light, while contrast is relatedto film processing.

Factors controlling amount of light exposure:

I- Using continuous light: two factors control light exposure

supposing film speed and light intensity are constant:

A) Aperture: “f -stop” or f/number, which was previouslymentioned and calibrated as 1.2, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32

and represents the diameter of lens opening (fig 29). The


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smaller the diameter of the lens opening, the lesser the amount

of light is passed (dark image) and the bigger the diameter ofthe lens opening, the greater the amount of light that can pass

(bright image).

Narrow aperture Wide aperture

Fig (29): Small f-stop [16] (narrow opening), (left) and wide f-stop [4], (wide openingright).

B) Shutter speed: which represents the duration the shutter screenremains opened. It is calibrated in a fraction of a second

(1/value) starting from 1second, 1/2, 1/4, 1/8, 1/15,1/30, …….1/2000 of a second (Fig 30 left). If the shutter speed

is too slow (30 or slower), the image may be blurred due toshaked camera and not due to wrong distance adjustment which

leads to double or even triple image of the object (right).

Fig (30): Shutter speed scale (left), image resulted from slow shutter speed (right).

In a constant light intensity and same film speed, it is a reversible relation between f-stop (diameter of the lens opening) and shutter speed (duration of

opening the shutter), so to maintain the same amount of light exposure, if we


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increase the lens diameter (more light is allowed), necessitates compensation

to reduce this increase by using higher shutter speed (decrease duration).

A fixed amount of light (Z) can be obtained from different combinations of

“f -stop” and shutter speed, that is to say:Z (fixed amount of light exposure) can be obtained from combination of f/11

and shutter speed 1/125 and the same (Z) light exposure can be obtainedfrom a combination of f/16 (smaller diameter) and shutter speed 1/60 (longer

duration) assuming the light power and film sensitivity are constant.Selecting specific combination depends on the photographic target (object to

be photographed) whether it is still or moving (will be discussed later).

NB: Intraoral photographs (still objects) needs close up position of the

camera and telephoto lens (macrophotography), so the depth of focus will be

shallow and critical, so compensation of light change should be by adjustingthe aperture on the expense of shutter speed which increases depth of focus.On the other hand photographing moving objects dictates increasing shutter

speed on the expense of aperture value to obtain fixed object in the image.

II-

Using snap light (flash): three factors affect the amount of light

received by the film:

A) F-stop (aperture) which is directly related to distance.B) Distance: as increasing the distance between light source (flash)

and the object, decreases the amount of light reflected from the

object (the light is distributed over a larger area), which needscompensation by increasing the f-stop (fig 30).

C) The power of the flash (guide number), the greater the guidenumber, the greater the light intensity and hence the bigger the

distance it can cover. The appropriate f-stop to the distance can

be calculated by dividing the guide number of the flash by the

distance (this is performed automatically in advanced camera

systems).

NB: It is important to notify here that shutter speed has no effect on theamount of light received by the film when using snap light source as the

flash releases the light in a speed much greater than any available shutter

speed (flash can reach a release speed of 1/30,000 of a second). On the otherhand, shutter speed may affect the image in other way if it is not

synchronized with the light release from the flash, i.e., the flash shouldrelease the light when the shutter screen is fully opened. Synchronization


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failure may produce a partially illuminated image (only part of the image is

illuminated), this is solved now in modern cameras.

Fig (30): Relation between distance and aperture to control light exposure.

- Color balance:

Color balance means producing an image with the same natural colors

of the object. Using artificial light source without correction will addunwanted hue to the image. The hue is the predominant wave length (color)

in the image (certain color of the light spectrum). Tungsten light source

(dental unit spot light) will add yellowish hue to the image, while fluorescentlight source may add greenish hue (fig 31). In the past, correction of color balance was done in the printing lab using special filters for corrections

(depending on understanding basic and complementary colors). Now, this procedure can be performed using photo editing software of the computers.

As mentioned before, good knowledge of basic and complementary colorswill help correcting this problem.

Fig (31): “A” Normal (natural) colors, “B” yellowish hue (when using tungsten light) and

“C” greenish hue (when using fluorescent light).

NB: Obtaining natural colors of the object in the image is important as colors have some

indications describing the clinical situations for example inflamed gingival is reddish incolor which should be presented as it is in the real situation.

(A) (B) (C)


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Technical image quali ty (photographic conditions)

This section of image quality depends on a good understanding of the basic photographic knowledge and the ability to apply it in a right way. Recent

photographic equipments solved most of the problems of optical image

quality as auto-focus techniques, auto-exposure metering systems, color balance, so most of the errors now may occur regarding the technical

prospective depending on the skill, performance and experience of the photographer.

Achieving such criteria depends not only how to see the object but also on

how properly to visualize the surrounding circumstances as proper retraction

of the lips, proper angle of the camera to the target which is summarized as“frame construction” which means what should be included in the frame?,

how big the object should be?, camera-to-object angle, and the ability to

reproduce these conditions in serial photographs either in one session assurgical procedures or in successive sessions as follow up of a procedure.Controlling these conditions will permit the photographer not only to

produce a high quality photographs, but also will be able to ensure

reproducibility of those conditions. Standardization of such conditions is thekey of high quality image production. This standardization will include:

1- Magnification (reproduction ratio)

2- Working Distance3- Camera-Object relation (vertical and horizontal)

1- Magnification (reproduction ratio): means how much the object will fillthe frame. Failure to obtain proper magnification will result either in too

small (fig 32 left) or too big (fig 32 right) object image, which willconsequently results in loss of details. This may be due to improper distance

(too far or too close), or wrong selection of the proper lens).

Fig (32): Undesired details are included in the left image (too far distance), while themolar area was not included in the right image. Both images are not accepted.


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2- Working distance: a sufficient working distance should be maintained to

avoid certain errors. Working too close to the object while using side or topmount flash will produce huge ugly shadows (if ring flash isn’t available).

This will increase shadow size (fig 33).

Fig (33): Too close camera with side light source will result in bigger shadow.

Dimensional distortion is another problem occurs when using too closedistance with wide angle lens (fig 34, left), which can be avoided by using

telephoto lens and slight increase the distance between the camera and theobject (fig 34, right).

Fig (34): Distorted proportions due to too close distance with wide angle lens (left), same patient with proper proportions (right), when using tele-photo lens.

3- Camera-object relation:If a ring flash is not available and a side mounted flash is to be used, a

simple hint is so useful to avoid unaccepted shadow. As a rule, a shadowoccurs opposite to the light source direction. So, when photographing the

right or left profile of a patient, if the light source comes from the side of the patient’s ear, the shadow will appear in front of the patient’s forehead and

nose, complicating the proper evaluation of the profile of the patient (fig 35,left). To overcome this problem, simply place the light source at the nasal


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side directing the shadow behind the patient’s head (away from the target

area fig 35 right).

Fig (35): Changing the light source direction will eliminate the undesired shadow (left),

giving clear details (right).

Camera-object orientationVertical and horizontal camera orientation affects the final outcome of the

image quality. For example, when photographing the intra oral frontal viewof occlusion, the camera should be parallel to occlusal plane (fig 36 a). If the

camera is too downward or too upward oriented, the image will give false presentation of the real clinical situation (fig 36 b and c).

(a)


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(b)

(C)

Fig (36): Well oriented horizontal plane (a), too downward camera position (b) and too

high upward camera position (c).

When capturing extra oral photographs, it should be kept in mind that theinter-pupillary line should be parallel to a horizontal plane (lower border of

the frame), or the produced image will be unsatisfactory (tilted) (fig 37).

Fig (37): Adjusting the horizontal plane to be parallel to the inter-pupillary line.

So before pressing the release button (before photographing), lot of pointsshould be kept in mind simultaneously:

- Framing the object properly.

-

Proper magnification.

- Sharp focusing on the most important point of the object.-

Proper orientation.


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-

Edges of the mirrors as well as fingers holding them should not be

visible.-

Avoid fogging formation on the mirror surface by either warming

the mirror surface, or instructing the patient to expire the air

through the nose.

Standardization of the photographic conditions, will not only help to producehigh quality photographs, but will also help for proper reproducibility of the

photographs after a period of time, enabling dentists, to evaluate thetreatment outcome as well as their own performance (Fig 38).

Fig (38): Standardized photographic conditions resulted in standardized photographs over

a period of time. Left picture shows a patient with extracted maxillary central

incisor. Right picture shows the same patient after insertion of removable partial

denture. Note that the magnification and camera orientation are nearly the same.


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Digital photography

Digital photography is electronically capturing and producing images usinga charge-couple device (CCD) which is the light-sensitive image device

within most modern cameras, containing hundreds of thousands of photo-

sites (pixels) that convert light energy into electronic signals. The more thenumber of these pixels; the more the data stored on the sensor and

consequently more stored fine details producing high image quality. This ishow image is stored on the electronic sensor to be retrieved later, transferred

to the computer or printed.

One of the most important advantages of digital photography is previewing

the captured images helped to detect any errors, replacing defective images by proper ones after correction and adjustment, but still the basic knowledge

is needed to properly evaluate the image and realize whether it is meeting

the needed quality criteria or not. Every device has its abilities and limits, so,understanding these abilities and limits of the device and working withinthose limits and abilities is more important than earning a highly

sophisticated device with shallow knowledge about the basic principals of

photography.

Digital photography follows the same rules of conventional (optical)

photography techniques and concepts with more advanced assistingtechnologies including automated exposure metering systems and auto-

focusing techniques. As in conventional cameras, range finder and SLR

digital cameras are available. The advantage of back screen (Fig 39, left) inrange finder digital cameras over rang finder optical cameras, is that it

solved the problem of parallax, as this back screen shows exactly what thesensor will receive. In addition, built-in zoom lenses and several program

modes facilitated the use of cheaper range finder digital cameras in some

dental photography situations. Still, SLR digital cameras have the advantage

of wide variety of interchangeable lenses with the facility of using different

light sources (ring flash, or light system).


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Fig (39): Range-finder digital camera with back screen (left) and DSLR digital camera(right).

What to look for in a digital camera? (Which Digital Camera?)

1- Mega-pixel: the greater the mega-pixel, the higher the image quality.The pixel is that smallest part of the receiver that can record light as

electronic signals in the charged-couple device (sensor) of the digitalcamera. At least 8 mega-pixel cameras will produce acceptable image.

Greater megapixel values will record more data and hence resulting ina better image quality (cameras with more megapixel value will be

more expensive).2-

Sensor size: CCD (sensor) has different sizes even in the same brand

name company (opposite to analogue cameras using films as imagereceiver which has a standardized size). The bigger the sensor size,

the bigger the pixel size (even in same amount of megapixels) whichenhances the image quality by reducing the noise around the main

signal. So, if we have two digital cameras having the same number of

pixels but Camera “A” with sensor size “X” will produce better image

quality of camera “B” with sensor size “1/2 X” 3-

In range finder digital cameras, optical zoom option is available. It is

the ability of the built-in zoom lens to actually magnify the image ofthe object. SLR digi tal cameras depend on the interchangeable lenses

with different focal lengths to produce good close up magnification.

In range finder digital cameras, optical zoom is more important than

digital zoom as the former is acting by real magnification while the

latter acts by enlarging a small area of the image and consequently itwill affect the image quality. To explain this, if we use digital zoomon a camera with 8 mega-pixel to get a double magnification, the

processor of the camera will use only 4 mega-pixel to stretch the

image over the area that was recorded over the whole 8 mega-pixel, so,

digital zoom enlarges a small part of the image and stretches it over a bigger area, but will not magnify the image of the object. Optical


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zoom option is expressed as “X” and the power is expressed in

number, i.e., [3X] optical zoom means the lens can give magnification3 folds from the same distance.

4- Macro photography option: it is the ability of the lens to get closer to

the target object (small minimal allowed distance).a.

In compact digital cameras, it depends on the optical zoom of

the lens and macro option of the camera. b.

In SLR cameras it depends on the focal length of the lens and

whether it has a built in macro ability or using additional closeup lenses (threaded in front of the lens)

Technical H in t: Confl ict between telephoto lens and macro option(F ig 40)

As mentioned before the minimum allowed distance (MAD) increases by

increasing the focal length of a lens but the maximum allowed distance is at

infinity. Macro option of a lens has a minimum and maximum alloweddistance, so there may be a shared range of focusing distances between theminimum allowed distance of the lens at normal setting and the maximum

allowed distance of macro option. Increasing the focal length of lens at the

normal setting decreases this zone, and higher focal length may result in a“0” zone preventing focusing adjustment when using high focal length with

macro option (Fig 40).

Fig (40): Conflict between normal focusing setting and macro option setting.


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Hand grip: too compact digital cameras (fig 41 A) (usually range finder type)

are not the best choice for dental photography as being too light and compactmay give the chance for slipping or changing the frame composition

adjusted by the photographer specially with beginners who have no

experience, leading to disappointing results regardless a proper sharpnessand lighting (brightness and contrast). Compact digital cameras with pop-up

flashes as a light source (Fig 41B), are not recommended as they will produce unpleasant shadow due to relative far position of flash unit from the

camera lens. If a compact digital camera is to be used, a camera design witha good hand grip and near flash unit to the lens is recommended for better

controlling camera handling and reducing shadow size (fig 41C).

A B CFig (41): Slim body and pop-up flash position compact digital cameras are not the best

choice (A & B), while digital cameras with hand grip and close flash unit to the

lens are superior (C).

It is important to note that we are not talking about different commercialnames, but, about the camera body design regardless the manufacturer’scompany.

NB: For digital cameras it is advisable to use the original lithium battery

(rechargeable) supplied with the camera, or if the camera uses the “AA” size batteries, it is recommended by most camera manufacturers to use

rechargeable batteries as it is the best for protecting the electric circuits from

electric shocks. Do not recharge non-rechargeable batteries as leakage may

occur damaging the internal parts of the camera. Keep your camera awayfrom dust, fluids and deposits to protect it from damage. If the camera is not

going to be used for more than 1-2 weeks, it is advisable to remove the batteries.


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Comparison between analogue (optical) and digital photography

Item Analogue Digital

Image Registration On film On CCD (electronic)

Image Processing Chemical Electronic

Image Retrieval Print on sensitive paper - On Camera Screen- On Computer Screen

- Print on sensitive paper- Print on normal paper

Preview Not Available Available

Image quality Depends on grain size Depends on pixel number

Compact cameras

Parallax Present Absent (by back screen)

Macro Absent Present

Optical Zoom Absent Present

Different program modes in the digital cameras and its meanings

Symbol MeaningThis option automatically select the desired program from the listed

modules according to the situation..

Program This option enables the camera to fully adjust the light exposure regardlessthe combination between shutter aped and f-stop

Av This represents Aperture value, indicating that the photographer selects theaperture value and the camera selects the relative proper shutter speed.

Tv (S) This represents time value where the photographer selects the shutter speed

and the camera selects the relative proper aperture.M Full manual control the light exposure adjustment.

MF Represents adjusting the focusing manually (manual focus)

AF Represents adjusting the focus automatically (auto focus)

Still photography mode

Macro photography option (close up, intra-oral)

Photographing portrait

Photographing moving objects (sports, wildlife, kids, with shutter speed).

For landscape photography (small aperture for large depth of field).

Night mode photography, when the background is dark, or just night lights,

the mode uses slow shutter speed and the flash lighten the faces.

Video mode

Viewing the captured saved images


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To erase unwanted saved images. A dialogue box appears to confirm that

the selected image is intended to be deleted.

ISO This option is included in the camera menu represents the calibration ofsensor sensitivity to the light which determines the amount of light

exposure needed to capture an image with accepted brightness . It’s

graduated as 80, 100, 200, 400, 800, 1600. The higher the ISO, the moresensitive sensor to light (needs less amount of light to produce proper brightness and contrast and is called fast film).

Er ror and Solutions

Error Solution

Blurred image Adjust focus and retake

Shallow depth of focus Adjust focal plane and retake

Fogging (cold mirror) Warm the mirror and retake

Extremely bright Retake (don’t adjust on computer)


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Extremely dark Retake (don’t adjust by computer)

Reflective background Change background and retake

Small target (wrong lens) Use telephoto lens and retake

Dimensional distortion (too closeto the object with wide angle lens)

Use telephoto lens and increase the distance


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Head tilting (vertical or horizontal) Adjust interpupillary line and retake

Shadow (wrong light direction) Change light source direction

Improper retraction Use proper retractor and retake

Uncentralized target (central incisor) Centralize the target and retake


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The next table will summarize some errors in the resulted image, its causes

and how to correct or avoid

Error Cause Action to correct

Blurred image* - Wrong distance adjustment

- Working beyond auto-focus limits

- Retake picture, avoid the

cause of the error

Shallow depth

of field*

- Too wide aperture

- Improper focal plane

- Retake picture, avoid the

cause of the error

Too bright - Over exposure ( in the manual mode)

- Working beyond exposure meter limits

- Can be adjusted in a photo-

editing computer software(within limits)

- Retake if too bright

Too dark - Under exposure ( in the manual mode)

- Working beyond exposure meter limits

- Reflective background

- Can be adjusted in a photo-

editing computer software

(within limits)

- Retake, change background

Too Smallobject

- Too far camera-object distance- Using wide angle lens

- Retake (don’t crop)

Abnormal hue - Artificial light (tungsten, florescent)- Improper adjustment of color mode

- Adjusted using a photo-editing computer software

Distorted

proportions*

- Using wide angle in a very close

distance

- Retake

Ugly shadowon the target

area*

- Using side or top mounted flash- Wrong light direction

- Retake and avoid the cause(use ring flash, or change

light source direction)

Ill defined

object from

background*

- Improper background color or nature

(reflective)

- Retake, change the

background

Un-centralized

object.

- Bad frame composition - Cropping using photo-

editing software

Items with (*) sign means it can not be corrected and should be repeated.


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Recent appli cation of photography:

Dental pictures can be used as a measuring tool in different purposes when areference tool is included in the picture. A color matching of dental crown

and/or bridge can be assisted by using an intraoral photograph with a shade

guide included in the picture (fig 42 left). Dental photographs may be alsoused in smile assessment researches when a ruler is included in the picture

(fig 42 right).

Fig (42A): Using photographs as a measuring tool with color reference included in the picture. Color

matching for a dental restoration, numerical values of the selected shade appears on the color picker option

of the software (left).

Fig (42B): Linear reference included in the image to calculate the magnification or reduction factor.


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Converting Old Analogue Stuff into Digital format:

A) Converting Old Printed Pictures:Sometimes, a digital camera can be used as a faster and easier alternative of

a flat b ed scanner for copying old printed photographs or papers. The same

basic photographic knowledge is applied with some modifications. Whencopying photographs, don’t use the flash unit as a light source as it will

produce annoying shadow spoiling the picture details (fig 43, left). Insteaduse day light or artificial light with color correction for such procedure for

better image quality (fig 43, right).

Fig (43): Left, copying pictures using flash unit with distorting reflection, right same picture copied using balanced light source.

B)

Converting Old Radiographs:

Recent techniques of radiograph production enables a digital copy of aradiograph whether conventional, CT, MRI or any other form, but

sometimes if we have old radiographs that have no digital copy which needsto be digitized. A digital camera may be an accepted alternative for highly

sophisticated expensive x-ray scanners for digitization of old radiographs(the radiograph film plate size may exceed the size of the scanning window

size of the scanner). Copying radiographic films using digital camerasdepends on the use of available light (as radiographic film viewer). Opposite

to object photography, radiographs needs the light source to be behind theradiograph passing through it to be photographed (transmitted light), so flash

light is not the suitable light source as it will not record data from theradiograph but will be reflected from the acetate base of the radiograph

giving disturbing reflections (fig 44 left). As the light source may not besufficient, the shutter speed may be so slow (30 or slower); depending on the

brightness of the radiograph, the camera should be as stable as possible.Holding the camera in hands may lead to blurred image due to shacked

camera during photography and slow shutter speed (fig 44 right), so it’sadvisable that the camera should be mounted on a tripod or on a copying


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stand (fig 45 left) to avoid such error to produce a high quality image of the

x-ray film (fig 45 right) .

Fig (44): Copying radiographs using flash unit leads to reflection (left) or usingextremely low shutter speed results in blurred image due to camera shake (right).

Fig (45): Copying stand (left) and perfect resulted image (right)


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Archiving the recorded images

Although computers helped a lot in proper archiving and retrieving theimages in a very easy way, standardization of work steps will make the

image transfer procedure easier. To separate between patients’ pictures

recorded on the digital camera, its worthy to photograph a paper recordingthe needed data about the patient including the name, date, diagnosis type of

treatment, stage of treatment (preoperative, postoperative or during) beforestarting photographing the patient. Then, in a customized folder, the

patient’s pictures should be saved, giving sufficient data for easier searchand retrieve (Fig 46).

Fig (46): Customized folder, including all patient’s photographs.

N.B.: A backup file is needed to ensure a rescue copy to avoid data

loss if any error occurs in the storage unit of the computer.


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When connecting the digital camera to the computer to transfer the

photographed images, a dialogue box is opened giving different optionsabout which software the user likes to use to transfer images (fig 47) , it’s

preferable to use the camera wizard option (left), as it gives the facility of

using customized file name including needed information with serialnumbering (right).

Fig (47): Camera wizard image transfer (left), and customized file name (right).


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Requi red photographs in dif ferent dental fields

As previously mentioned, any invasive procedure should be photographed

preoperatively, and postoperatively. Required photographs differ according

to the dental specialty.

1- Oral Surgery

A- Osteotomy operationsi- Extra-oral shots

- Frontal face - Frontal smiling

- Lateral profile (right and left) - 45° profile (right and left)

ii- Intra-oral shots

- Occlusion (frontal) - Occlusal views (upper and lower arches)

- Occlusion (side view), right and left. - Maximal opening

B- Fracture

i- Extra-oral shots

- Frontal face - Lateral profile (right and left).- 45° profile (right and left)*

ii- Intra-oral shots- Occlusion (frontal) - Occlusal view (affected arch only)

- Occlusion (side view), right and left. - Maximal opening

- Protrusive position - Lateral excursion (right and left)*.

C-

TMJ- As in fracture cases.

D- Miscellaneous

2- Orthodontics

- As in oral surgery for patients undergoing osteotomy operations

3- Fixed prosthetics

A) Intra-oral

- Occlusion (frontal) - Occlusal view (affected arch only)

- Occlusion (side view), right and left.

4- ImplantologyA- Intra-oral

- Occlusion (frontal) - Occlusal view (affected arch only)

- Occlusion (side view), right and left.

5- Miscellaneous


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Definitions

Aberration : failure to collect light beam in he same focus. [p 9]

Achromatic lens : a lens that can collect red and blue wave lengths in the same focus

point. [p 9]

Aperture : diameter of lens opening allowing light to pass through. [p 10]

Apochromatic lens : a lens that can collect red and blue and green wave lengths in the

same focus point. [p 9]

ASA: A number set by the American Standards Assoc., which is placed on film stock tomeasure sensitivity to light. (not used now)

Basic colors : Red, Blue, Green (identified by visual receptors of the eye) [p 4]

Brightness : amount of light reflected b the object. [p 19]

Complementary colors : Cyan, Yellow, Magenta (colors opposite to basic colors). [p 5]

Contrast : difference between dark and light areas of the image. [p 20]

Deflection : deviation of light beam from its straight course when passing in two different

media (air and water or air and camera lens). [p 4]

Depth of fi eld (DOF) : part of the image lying in sharp focus. [p 17]

Digital photography : it is electronically capturing and producing images using a charge-

couple device (CCD). [p 29]

DIN : DIN, an acronym for the German Deutsches Institut für Normung (German

Industrial Standard), found 1917 (German measure for film sensitivity).

F lash guide number : light intensity produced by a flash unit. [p 10]

Focal Length : the distance between focus point and center of the lens when the distance

scale is set at infinity (∞).[p 8]

Focal plane : the point at which the distance scale is adjusted. [p 18]

Focus point : the point at which the sharpest image is formed. [p 8]

Ghost image : secondary image produced by a rear-surface glass mirror. [p 13]

Hue (color balance) : the most dominant wave length (color) in an image. [p 23]


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I SO : Used for film sensitivity calibration in all digital cameras established by

International Standards Organization. [33]

Lens : Special apparatus which collects light in the focus point. [p 8]

Macro photography : The ability to get closer to the target object. [p 30]

Optical image quali ty : image quality related to optical bases. [p 16]

Optical zoom : ability of a zoom lens in a digital camera to actually magnify the targetobject. [p 30]

Parallax : difference between two views of two lenses (range finder cameras) [p 6]

Photography : comes from the two Greek words: “photos” which means light and

“graphos” which means drawing”. [p 1]

Pixel : the smallest unit in the CCD than can register data. [p 30]

Primary image : the image reflected by the reflecting surface of a mirror. [p 14]

Ring f lash : circular flash unit mounted by screw in the lens. [p 12]

Sharpness : well defined boundaries of the image components. [p 17]

Shutter speed : time the shutter screen remains open to expose the film. [p 21]

SLR camera : Single Lens Reflex camera. [p 7]

Standard l ens : a lens with focal length of 45-55 mm (has the same angle of vision of the

human eye). [p 9]

Technical image quali ty : image quality related to the skill of the photographer. [p 16, 24]

Tele-photo lens : a lens with focal length greater than 55 m (has narrower angle of vision

than the standard lens). [p 9]

Wide angle lens : a lens with focal length smaller than 45 mm (has wider angle of visionthan the standard lens). [p 9]

Zoom lens : a lens with interchangeable focal length. [p 9]


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Some hints and ti ps-

Obtaining pure gray color in the image means all other colors are

balanced to natural colors as in real (which has important

indication in image interpretation).

-

Metal retractors were used in the past as they could be sterilizedand autoclaved but recently plastic retractors are made of

autoclavable materials.-

Brightness is related on film exposure to light, while contrast is

related to film processing.

-

Intraoral photographs (still objects) needs close up position of the

camera and telephoto lens (macrophotography), so the depth offocus will be shallow and critical, so compensation of light change

should be by adjusting the aperture on the expense of shutter speedwhich increases depth of focus. On the other hand photographing

moving objects dictates increasing shutter speed on the expense ofaperture value to obtain fixed object in the image.

- It is important to notify here that shutter speed has no effect on theamount of light received by the film when using snap light source

as the flash releases the light in a speed much greater than anyavailable shutter speed (flash can reach a release speed of 1/30,000

of a second). On the other hand, shutter speed may affect the imagein other way if it is not synchronized with the light release from the

flash, i.e., the flash should release the light when the shutter screen

is fully opened. Synchronization failure may produce a partiallyilluminated image (only part of the image is illuminated).-

Obtaining natural colors of the object in the image is important as

colors have some indications describing the clinical situations forexample the image of an inflamed gingival should have reddish

hue to simulate the natural situation.-

For digital cameras it is advisable to use the original lithium

battery (rechargeable) supplied with the camera, or if the camerauses the “AA” size batteries, it is recommended by most camera

manufacturers to use rechargeable batteries as it is the best for

protecting the electric circuits from electric shocks. Do notrecharge non-rechargeable batteries as leakage may occur

damaging the internal parts of the camera. Keep your camera away

from dust, fluids and deposits to protect it from damage. If thecamera is not going to be used for more than 1-2 weeks, it is

advisable to remove the batteries.


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-

Warming the intraoral photographic mirrors will help avoiding

fogging (specially in cold weather), but don’t overheat the metalmirrors (warm it from the rear surface not the glazed front surface).

- Don’t use wide angle lens with close up photography as it will

cause dimensional distortion (elongation of the middle third andcompression of the peripheral 2/3).

- Reflective background may not only disturb the vision, but mayalso lead to dark image (as it may disturb the function of the

exposure metering system).-

Blurred image may be due to incorrect focus adjustment, but may

also occur even with autofocusing system if the working distance

is beyond the autofocusing system limits.- Blurred image may also occur when using continuous light source

if the shutter speed is too slow (less than 1/125) specially, if the

camera isn’t mounted on a tripod. - When photographing highly reflective objects (metal partial

denture base, orthodontic brackets, metallic hand instruments,……)

a light system composed of indirect light sources is better than

using single flash unit as a light source, even if it is a ring flash (itmay make produce highly reflective surface of the reflective

objects)

ah practical photography master 2012.pdf

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