pinhole photography ed 2

7/27/2019 Pinhole Photography Ed 2

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Pinhole Photography 129

A number o dedicated individual s have paved theway or the invention o photography with their ac-complishments in several areas o natural sciences.

However, in very basic terms, photography is basedon only one condition to be satised, the successulcombination o image ormation and image capture.

Image capture has been a chemical domain orover 150 years, but modern electronics recently addeddigital image capture as a realistic alternative andprovided us with resh tools or image manipulation.Image ormation, on the other hand, was alwaysgoverned by the laws o optics. It may be o historicinterest that image ormation and capture were prac-ticed independently or some time, beore they were

successully combined to make photography possible.

Pinhole Photography

The fascinating world of lensless imagingby Ralph W. Lambrecht

200

1

byAndreasEmmel,allrightsreserv

ed

fg.1 (top) This is thought to be the frst published picture

o a camera obscura and a pinhole image, observ ing

the solar eclipse o 1544-Jan-24, in the book De Radio

Astronomica et Geometrica o 1545 by Gemma Frisius.

fg.2 (right) A pinhole image made with a 11x14 large-

ormat camera shows surprising detail and clarity.


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130 Way Beyond Monochrome

1

2

A

B

2

1

A

B

2

1A

B

Nevertheless, taking a closer look at these buildingblocks o photography, one quickly nds that imageormation is ar older than image capture.

Basic image ormation is as old as nature itsel.

The simplest arrangement or basic image ormationis by way o a pinhole. The overlapping leaves in treesorm numerous pinholes naturally, through whichcountless sun images are projected onto the ground.It is conceivable that humans were captivated by thecrescent pinhole images o an eclipsed sun as early asthe dawn o mankind.

The earliest known description o pinhole opticscame rom Mo Ti in China rom around 400 BC,and Aristotle wrote about his observations on the

ormation o pinhole images in 330 BC. The rstknown proposals to create a small opening in anotherwise darkened room (camera obscura), in orderto intentionally produce pinhole images, came rom

Alhazen in Egypt around 1020 AD and Roger Bacon(1219-1292) in England. Obsessed with representingrealistic perspectives, Renaissance artists, includingLeonardo da Vinci (1452-1519), oten used a cameraobscura to develop the undamental sketches or theirmagnicent paintings. In 1584, the second edition oGiovanni Battista Della Portas book Magia Naturalis

was published. In this book, he described the ormationo pinhole images and the construction o a pinholecamera in detail. Around that time, Johannes Kepler(1571-1630) coined the phrase camera obscura, whichliterally means dark room. Soon ater, many pinholes

were replaced by a simple concave lens, which improvedimage brightness and quality. It took over 200 hundredyears, until ater the invention o photography, or therst revival o pinhole imaging around 1850.

Image FormationImage ormation starts with light rays, which areeither emitted or refected by the subject. The lightalling onto an opaque subject is partially absorbedand partially refected. Theoretically, refection is ei-ther directional (specular) or multidirectional (diuse).In reality, the actual refection depends on the suracecharacteristics o the subject and is always a mixtureo specular and diuse refections. Smooth suraces,like glass, mirrors, polished metal or the calm suraceo a lake, create predominantly specular refections.

Rougher suraces, like leaves, stone, cloth or dry skin,create primarily diuse refections.

fg.3a Holding up a card in ront o a

subject, because every point on

the card receives light rays rom

numerous points o the subject.

fg.3b An opaque panel, containing a tiny

pin-sized hole, is placed between

the subject and the card. The panel

blocks all light rays coming rom

the subject with the exception

o the limited number entering

through the pinhole. The small

hole restricts every image point

on the card to only receive light

rays rom a confned region o the

subject, orming countless blurry

image circles and a uzzy image.

fg.3c To improve image quality, the

pinhole is replaced by a lens. It

converges several light rays rom

the same subject point into one

ocused image point. This makes or

a sharper and brighter image than

a pinhole can possibly provide.


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do not cost a lot, which makes them ideal, becausethey are also extremely precise in diameter and havea particularly smooth edge (g.4b). Nevertheless, iyou are in a rush, or just want to experiment with a

pinhole, you can simply take a pushpin or sewingneedle and orce it through a black piece o cardboard(g.4a). This will make or a workable pinhole, butdont expect an optical miracle, because the roughedge will signicantly degrade image quality.

I you aim or more accuracy, consider the ollow-ing work instructions illustrated in g.5. This will notprovide you with a pinhole o ultimate precision, but

with a bit o practice and the right materials, a good-quality pinhole can be made within a ew minutes.1. Using scissors, cut a piece o metal rom brass oil,

or aluminum can, to roughly 15x15 mm in size.2. Place the metal fat onto a sot wood support, and

rmly press a ballpoint pen into the center o thesquare, creating a clearly visible indent.

3. Turn the metal over, and use ne sandpaper to grindaway the bump without penetrating the metal.

4. Create the pinhole by pushing a needle into thecenter o the indent, and gently reinsert the turningneedle rom the other side to smooth the edge.

For the purpose o investigating general imageormation, we can saely assume that every pointo an illuminated subject emits or refects light intomultiple directions. Holding up a card in ront o such

a subject, in an otherwise darkened room, will notorm an image on the card, because every point onthe card receives light rays rom numerous points othe subject (see g.3a). Consequently, image ormationis not possible, because every potential image pointreceives light rays rom multiple subject points.

The simplest arrangement or image ormation isachieved by placing a fat opaque object, containing atiny pin-sized hole, between the subject and the card(see g.3b). The opaque panel blocks all light rays

coming rom the subject with the exception o thelimited number entering through the pinhole. Thehole is small enough to restrict every image point onthe card to only receive light rays rom a connedregion o the subject, orming countless blurry im-age circles, which together orm a dim uzzy image.This way, compromised image ormation is possible,because every potential image point receives light raysonly rom a limited number o subject points.

As we can see, expensive optic s a re not essentialto the image-orming process, but to improve image

quality beyond the pinhole, the opening must bereplaced by a concave lens. The lens converges severa llight rays rom the same subject point into one ocusedimage point through reraction (see g.3c). This makesor a sharper and brighter image than a pinhole canpossibly provide. High-quality image ormationis only possible with a lens, where every potentialimage point exclusively receives light rays rom itscorresponding subject point. Nevertheless, pinholephotography oers a subtle beauty, dicult to achieve

otherwise, and thereore, it is worthwhile to exploreand optimize this ascinating eld o photography.

Making Your Own Pinhole CameraThe rst step in building a pinhole camera is to obtainthe pinhole itsel. A high-quality pinhole is accuratein diameter and has a smooth perimeter or superiorimage clarity. The smoother the edge o the pinhole is,the sharper the resulting pinhole image will be. Youcan buy a pinhole or make one yoursel.

Several suppliers o optical and scientic products

sell laser-cut pinholes, which are typically dr illed intothin brass oil. Proessionally-made, laser-cut pinholes

narrow

normal

wide

fg.4b (let) A laser-cut pinhole, having a

particularly smooth perimeter, gives

the best possible image quality.

fg.4a (ar let) Simply orcing a needle

through a piece o cardboard will

result in a workable pinhole, but the

rough edge degrades image clarity.

a b c d e

indentationaftergrinding

finishedpinhole

thinpieceofmetal

ballpoint pen

soft wood support

sewing needle

fg.5a (below let) With a little bit o

practice and the right materials,

a good-quality pinhole can be

made within a ew minutes.

fg.5b (below) The pinhole material

thickness determines the angle o

view. Thick materials make or a

narrow angle o view and may not

fll the entire negative ormat.


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detail and clarity, because the maximum resolutionpossible with contact-printed pinhole images (seeg.14) is approaching the resolving power o standardhuman vision, which is around 7 lp/mm.

Medium-ormat box cameras oer the opportunityor a more permanent pinhole conversion. Old medi-um-ormat box cameras are available in abundance onthe used-camera market and can be obtained or littlemoney. However, be certain to hunt or a model that

works with the common 120-lm ormat. This ormatwas introduced in 1901 by Kodak or their BrownieNo.2 and is still manuactured today, because it is usedin all modern medium ormat cameras. Fig.6 shows mymedium-ormat pinhole camera, based on a well-kept

Balda Poka, which was made in Germany around 1930.I paid less than $15 or it in an internet auction. Thesimple meniscus lens was removed and replaced with a0.38mm laser-cut pinhole. This is an ideal diameter orthe 6x9 negative ormat and the 105mm ocal length.The working aperture computes to /278 or /256 anda 1/3 stop. The shutter has two settings, 1/30 s andB. For the long exposures, which are typical or thesmall apertures in pinhole photography, I use the Bsetting exclusively and chose to keep the shutter openby securing the release lever with a rubber band.

The pinhole material thickness is o some conse-quence to the pinhole image, because it determinesthe angle o view. A thickness o about 0.1 mm is ideal,because it provides a viewing angle o over 125. Thicker

materials make or a narrower angle o view and maynot always ll the entire negative ormat (see g.5b).

It is a good idea to measure the pinhole diameterbeore the pinhole is mounted to a camera body. Itis hard to do aterwards, and without knowing thesize o the aperture, we cannot accurately determinethe working /stop o the pinhole camera. Unless youhave access to a microscope with measuring capability,simply magniy the pinhole by available means. Usea slide projector, the darkroom enlarger or a scanner

to perorm this task. First, prepare a measurementsample, or example two lines 20 mm apart, andenlarge or scan this sample to determine the magni-cation actor. Finally, enlarge or scan the pinhole atthe same magnication, measure the projection or thescan and calculate the actual diameter o the pinhole.The working /stop o the pinhole (N) is given by:

where d is the diameter o the pinhole, and isthe ocal length o the pinhole, which is the distancebetween the pinhole and the lm plane, assuming thata pinhole camera is always ocused at innity.

Almost any container can be turned into a pinholecamera body as long as it can be made absolutely lighttight. Popular items include cardboard or metal boxeso all sizes, as well as cylindrical storage containers orood, chemicals or rolls o lm. Anything rom 35mmlm canisters to ull-size delivery vans has been con-

verted to portable pinhole cameras. Best suited, andar more practical, are old or existing camera bodies.They are already designed to saely hold and transportlm, and with the exception o view cameras, most othem oer some kind o viewnder to compose theimage and a shutter to control the exposure.

Fig.2 shows a pinhole image that was taken with asel-made 11x14 large-ormat view camera. It takes aminimum amount o eort to convert a view camerainto a pinhole camera. Temporarily mounting a pin-hole into an empty lens plate is all one has to do to

nish the conversion. This small endeavor is rewardedwith large negatives and pinhole images o surprising

Nf

d=

fg.6 Old medium-ormat camera

bodies make perect pinhole

cameras. This shows a well-kept

6x9 box camera rom around

1930 ater the conversion.

fg.7 (ar right) Pinhole images have

an almost endless depth o feld

combined with beautiul image

sotness. This image sotness is

partially caused by diraction but

also by motion blur, due to thetypically long exposure times.


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or the optimal pinhole diameter. The image clarityo lens-based photography is limited by lens aberra-tions and diraction. Closing the aperture reduceslens aberrations signicantly but slowly increases thedegrading infuence o diraction. This improvesthe overall image sharpness up to a point, but withdecreasing apertures, diraction eventually becomesthe only limiting actor o image clarity. Obviously,a lens-less pinhole does not suer rom lens aberra-

tions, but the image clarity o pinhole photographyis considerably limited by diraction.

Simple geometric optics dictates that the optimalpinhole is as small as possible, because the smallerthe hole is, the smaller the uzzy image circles are(see g.3b), and the sharper the pinhole image willbe. However, this ignores the infuence o di raction,

which causes the light to spread, as it passes throughthe narrow aperture, and increases the size o the uzzyimage circles. Diraction optics dictates that the pin-hole is as large as possible to minimize light spreading.

As a consequence, the ideal pinhole diameter is assmall as possible and as large as necessary.

In 1857, Pro. Joseph Petzval was apparently therst in trying to nd a mathematical equation or theoptimal pinhole diameter. Being in disagreement withhis proposal, Lord Rayleigh published a competing or-mula in 1891, which gave a much larger diameter, andso did William Abney in 1895 with yet another equa-tion. All three attempts were based on geometric optics,but no consensus was reached among photographers to

which the true optimal pinhole diameter was. Moreequations, this time mainly based on empirical studies,

fg.9 Most equations to calculate the

optimal pinhole diameter (d)

ollow the ollowing ormat:

where l is the wavelength o

light, is the ocal length o

the pinhole, and k is a constantvalue, typically between 1 and 2.

The simple snapshot in g.7, which was takenwith the converted medium-ormat camera in g.6,illustrates the almost endless depth o eld in pinholephotography. When selecting a camera body or a

pinhole conversion, be aware that many old medium-ormat cameras have a small red window at the back.This window is part o the manual lm advance systemand is provided to identiy the currently set negativerame. The 120 roll-lm ormat has the rame numberso all popular medium negative ormats printed onthe outside o the backing paper, and they can be seenthrough the window. To protect the lm rom harm-ul light entering through the window, it is made ored-tinted glass or plastic. This protection works well

or orthochromatic lms but is not a reliable saeguardor modern panchromatic lms. Beore you load thecamera with panchromatic lm, cover the red window

with a piece o black tape rom the outside. Wheneveryou need to advance the lm, shade the window withone hand and careully pull the tape aside with theother. Then, orward the lm to the next rame andquickly cover the red window with the tape again.

Ana log or digital small-ormat SLRs are easi lyconverted to sophisticated pinhole cameras by sac-ricing an opaque body cap. The distance rom the

cameras lens mount fange to the lm or oca l planeis, thereore, an approximate measure or the ocallength o the pinhole. Drill a hole into the center othe body cap, and cover it by taping an appropriatepinhole to the back (g.8). Keeping the modied capin the camera bag oers a quick conversion betweenlens and pinhole imaging.

As with lens-based images, the qual ity o pinholeimages goes up with negative size. This may be osome consequence or images, which mainly requirealmost endless depth o eld. Nonetheless, it is im-portant to realize that the beauty o pinhole images islargely based on their di raction-limited perormance.The inherent uzziness makes pinhole cameras per-ectly suited or all those photographic subjects wherean image will benet rom a little sotness or romanticmystery. I pinhole images would be perectly sharp,there would be little reason to make them.

The Optimal Pinhole DiameterRealizing that pinhole images can never be perectly

sharp has not stopped photographers rom seeking tooptimize the quality o pinhole images and searching

fg.8 Analog or digital small-ormat

SLRs are easily converted to

sophisticated pinhole cameras by

drilling a hole into a spare body

cap and flling it with a pinhole.

d k f= l


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fg.10 The optimal pinhole diameter (d)

to optimize image sharpness is

derived rom the Airy disc by:

where l is the wavelength o

light, N is the pinhole aperture

in /stops, and is the ocal

length o the pinhole.

means that they provide a depth o eld rom thehyperocal distance to innity. In both equations, thepinhole diameter is a unction o the wavelength olight and the ocal length o the pinhole, but a dier-ent numerical constant is used in each ormula.

In 2004, Kjell Carlsson o the Royal Institute oTechnology in Stockholm, Sweden conducted an

evaluation o a variety o pinhole sizes. Unique to hisapproach was the act that he stayed clear o subjec-tively comparing photographs. Instead, he computedMTF data or a number o dierent pinhole diametersand compared their MTF graphs. Fig.11 shows an ex-ample comparing the two proposed pinhole apertures.The diameter o equation (1) is derived rom the Airydisc, and the diameter o equation (2) is based on theRayleigh criterion. The comparison illustrates the

ollowed until well into the 20th century. Many equa-tions perormed good enough to nd enthusiasticollowers, making it even more dicult to agree to oneoptimal pinhole diameter. In retrospect, it seems like

a twist o ate that Lord Rayleigh did not consider theresearch on diraction by Sir George Airy rom 1830,or his own diraction criterion, which he publishedalmost 20 years prior to oering his pinhole equation.Because, with his in-depth knowledge o diractionand photography, he held the key to nding the idea lpinhole diameter, everyone can agree to.

Remember that diraction optics dictates thatthe pinhole is as large as possible to minimize lightspreading, and that geometric optics dictates that an

ideal pinhole is as small as possible to optimize imageclarity. Considering the Airy disc and the Rayleighcriterion leads us to two theorems or an ideal pinholediameter and suggests that there may be more thanone right answer.1. The smallest pinhole possible is based on the Airy

disc to optimize image sharpness.

2. The largest pinhole necessary satises the Rayleighcriterion to optimize image resolution.

Both equations are derived, as shown in g.10,either rom the Airy disc or the Rayleigh criterion.Innity ocus is assumed or both, which in reality

d N

df

d

d f

d f

=

=

=

=

2 44

2 44

2 44

2 44

2

.

.

.

.

l

l

l

l

1.0

0.8

0.6

0.4

0.2

0.0

0 10 20 10090807060504030

spatial frequency [%]

modulationtran

sferfactor

more contrast

higher resolution

1

2

fg.11 The MTF graph compares the perormance o two

pinhole diameters. One oers more contrast and

perceived sharpness, while the other provides more

detail and resolution. (MTF data courtesy o Kjell Carlsson)

d f= 3 66. l

d f= 2 44. lfg.12a-b (below) The test images in a)

were taken with a small pinhole,

based on the Airy disc, and

the images in b) with a largepinhole, based on the Rayleigh

criterion. The small pinhole in

a) oers more contrast, while

the large pinhole in b) provides

more resolution. Most observers,

however, perceive the high-

contrast images on the let as

being sharper o the two sets.

d f= 2 44. l d f= 3 66. la) b)


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Pinhole Aperture, Exposureand Focus

As we saw in ig.5a, regula r sew ingneedles are convenient tools to create

quality pinholes. Since the beginningo the 19th century, needle sizes are de-noted by numbers, and the conventionis that the thickness o a needle increasesas its number decreases. In other words,the higher the needle number, the thin-ner the needle. Fig.14 identies the mostappropriate needle number to create apopular pinhole diameter.

Fig.14 also shows the approximate

pinhole aperture in /stops with 1/3-stopaccuracy. Use this aperture or all expo-sure calculations or measurements, anddont orget to consider lm reciprocity,as exposure times are likely long enoughor reciprocity to have a signicant e-ect. Most general-purpose lightmetersdo not have aperture settings beyond/64. This makes their applicationsomewhat cumbersome or pinholephotography, where apertures o /256

and smaller are the norm. However,g.14 provides exposure compensationor all /stops in relation to /64. Setyour lightmeter to /64 to determinethe exposure, and extend the exposuretime according to the indicated /64compensation or your pinhole aperture.

You wil l nd a special Pinhole Dialin the appendix under Templates tosimpliy this task.

Most pinhole cameras do not provide any type oocus adjustment, and thereore, a pinhole camera isassumed to be ocused at innity. This means that thedepth o eld extends rom the hyperocal distance toinnity, and the hyperocal distance is the ront ocuslimit. A look at the hyperocal distance in g.14 de-mysties why pinhole cameras are considered to havealmost endless depth o eld. At /256 pinhole ocusamazingly extends rom 270 mm to innity.

Depth o eld can be extended even urther ithe pinhole camera provides some kind o a ocus

adjustment, as it would in a view camera conversion.Maximum depth o eld is obtained i the pinhole

focallength

[mm]

pinholediameter

[mm]

maxresolution

[lp/mm]

f/64rel exp

[stops]

needle[number]

aperture

35

45

55

75

90

135

150

180

210

300

450

600

800

0.22

0.25

0.27

0.32

0.35

0.43

0.45

0.49

0.53

0.64

0.78

0.90

1.04

-

15

14

13

12

11

10

10

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8

6

4

3

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f/180

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105 0.38

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8.1

7.3

6.3

5.7

4.7

4.4

4.1

3.8

3.1

2.6

2.2

1.9

5.3

hyperfocaldistance

[mm]

105

135

165

225

270

405

450

540

630

900

1,350

1,800

2,400

315

pinholeextension

[mm]

18

23

28

38

45

68

75

90

105

150

225

300

400

5311 f/256

f/256

f/256

f/360

f/360

f/360

f/512

f/512

f/720

+2

+3

+3

+3

+4

+4

+4

+4

+5

+5

+5

+6

+6

+7

0

0.2

0.4

0.6

0.8

1

1.2

20 100 1,000

optimalpinholediameter[mm]

focal length [mm]

d f= 1 56. l

fg.13 The optimal pinhole diameter or perceived sharpness

is based on the equation or the Airy disc.

perormance dierence o the two ormulas, but italso reveals why an agreement or the optimal pinholediameter was so dicult to achieve. Equation (1) oersmore contrast and perceived sharpness, while equation

(2) provides more detail and resolution.A set o test images in g.12 veries the theoretical

evaluation. A small-ormat digital SLR (see g.8) wasequipped with a small pinhole, based on the Airy disc(0.25 mm), to create the images in g.12a and a largepinhole, based on the Rayleigh criterion (0.30 mm),to create the images in g.12b. The images in g.12ahave more contrast and appear to be overall sharperthan the images in g.12b, as seen in the license plates,

while the images in g.12b have more resolution, as the

bar charts reveal. Unortunately, this leaves us withtwo dierent proposals or an optimal pinhole diam-eter, one or contrast and one or resolution. Beore weagree to just one optimal pinhole diameter, we need todecide which o the two we want to optimize.

The quest or the optimal pinhole diameter isgenerally ueled by the desire to create the sharpestpinhole image possible. Contrast and resolution areboth aspects o sharpness, but as demonstrated ing.12, human perception typically considers high-contrast images to be sharper than high-resolution

images. Consequently, unless resolution is moreimportant than perceived sharpness, my proposal orthe optimal pinhole diameter (d) is based on George

Airys diraction-limited disc:

or in the more conventional ormat:

where l is the wavelength o light, and is theocal length o the pinhole. A common value or the

wavelength o light is 555 nm (0.000555 mm), which isthe eyes sensitivity peak and an appropriate value orstandard pictorial photography. For inrared photog-raphy, use the lms spectral sensitivity instead.

Fig.13 shows how the optimal pinhole diameterincreases with ocal length, and g.14 provides useul

data or some popular ocal lengths to help with thedesign, exposure and composition o pinhole images.

d f= 2 44. l

d f= 1 56. lfg.14 This table provides useul data

or some popular ocal lengths to

help with the design, exposure and

composition o pinhole images.

a) optimal pinhole diameter

b) needle number to make pinhole

c) working aperture in 1/3 stops

d) exposure compensation relative

to /64 exposure measurement

e) maximum pinhole resolution

) hyperocal distance

g) pinhole extension required toocus at hyperocal distance


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A zone plate (g.16b) consists o a center hole,which has the same diameter as the optimal pinhole,and an arbitrary number o concentric rings or zones,alternating between opaque and transparent. The

outer diameter or each zone (dn) is given by:

where l is the wavelength o light, is the ocallength o the pinhole, and n is the sequential numbero the zone. It is important to note that each zone,opaque or transparent, has the same surace area asthe center pinhole. This means that a zone plate withseven additional transparent zones has eight times thelight-gathering power o the pinhole alone, which isequivalent to an aperture improvement o +3 stops.

Another pinhole alternative is a multi-pinhole solu-tion, also called mega pinhole or photon sieve. Insteado using the entire ring o a diraction zone, as in thezone plate, an arbitrary number o small pinholes aredistributed along the theoretical zones o the photonsieve, orming a hole pattern or each diraction zone.

While the di raction zones are getting thinner andthinner as they are rippling away rom the center

pinhole, the patterns holes are getting smaller andsmaller towards the outside o the photon sieve. Thedesign in g.16c distributes just enough holes on eachzone to total hal the surace area o the center pinholeor each hole pattern. This means that a photon sieve

with six additional hole patterns has our times thelight-gathering power o the pinhole alone. This isequivalent to an aperture improvement o +2 stops.

Its impossible to cut or drill zone plates and photonsieves like pinholes. The best way o making them is tocreate an enlarged, tone-reversed drawing o the design,and photographing it onto high-contrast B&W lm,thus reducing it to the right size. Such a design proposalis available in the appendix under Templates.

The trade-o or the increased light-gatheringpower with zone plates and photon sieves are a reduceddepth o led and a loss o image qua lity, as the resulto the larger apertures and the less than perectlytransparent materials to make them. Nevertheless, ormany photographers, the unique image characteristicso these special apertures make more than up or all

their disadvantages. The same is true or pinholesimages in general. They are well worth a try.

is ocused at the hyperocal distance, in which case,depth o eld starts at hal the hyperocal distanceand extends to innity. O course, visual ocusing isimpossible with small pinhole apertures and the dim

images they create. That is why the last column ing.14 provides a dimension or the pinhole extension.Extend the pinhole-to-lm distance by this amountin order to ocus the image at the hyperocal distance.

As with all close-up photography, moving the pinholecloser to the subject moves it away rom the lm andthis reduces lm illumination. This must be compen-sated with an increase in exposure time, and in case othe optimal pinhole diameter, an exposure increase o1 1/6-stop is required or hyperocal ocusing.

Pinhole AlternativesThere is hardly another eld in photography, whichinvites more to experimentation than pinhole photog-raphy, and modiying the pinhole aperture is a creativemethod to produce endless possibilities or imagealternatives. I the aim is image clarity, a plain circularhole o optimal diameter is hard to beat, but i you liketo explore unconventional substitutes, try apertures oall shapes, including horizontal, vertical and wavy slots.More technical aperture alternatives or pinholes are

diraction zone plates and photon sieves.Lenses produce images through reraction, pinholes

produce images through diraction. With zone platesand photon sieves (g.16), photographers take ulladvantage o diraction by creating apertures thatsimulate the Airy di raction pattern. Both have largerapertures and require less exposure than plain pinholesbut produce uzzier images with less depth o eld.

d1

d2

d3

a

pinhole

b

zone plate(+3 stops)

c

photon sieve(+2 stops)

10

9

8

7

6

5

4

3

2

10 -1

21EV

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14

131211

1'2'

4'

8'

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30'

1h

2h

4h

8h60

30

15

8

4

2

30"15"

8"

4"

2"

1"

IV

III

II

I

0

VIV

VII VIIIIX

X

25618012890

45

6436

0512

720

1k

-4-3-2

-1

0-5

-6

-7

-8

PinholeDial

2008

RalphW.

Lambrecht

www.dark

roomagic.

com

f/stop

Time

EV

EV

fg.15 In the chapter How to Build and

Use a Zone Dial, a useul Zone

System dial is presented or general

exposures. Pinhole photographer

will be happy to know that they can

also fnd a special pinhole version

in the appendix under Templates.

fg.16 Di raction zone plates and

photon sieves are alternatives

to a plain pinhole. They have

larger apertures and require less

exposure but produce uzzier

images with less depth o feld.

d f nn = 1 56. l

pinhole photography ed 2

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