photography: 2 - lens sizes and depth of field

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Lens sizes Depth of Field

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Page 1: Photography: 2 - Lens Sizes and Depth of Field

Lens sizesDepth of Field

Page 2: Photography: 2 - Lens Sizes and Depth of Field

Camera lenses come in different sizes:

Page 3: Photography: 2 - Lens Sizes and Depth of Field

The longer the lens the more it enlarges the object being photographed

Page 4: Photography: 2 - Lens Sizes and Depth of Field

Lens are measured in mm… 50mm is roughly the same as what we see

with the human eye:

Page 5: Photography: 2 - Lens Sizes and Depth of Field

Less than 50mm (typically 24-30mm) gives wide angles:

Page 6: Photography: 2 - Lens Sizes and Depth of Field

And more than 50mm (typically 70mm+) zooms in on a subject:

Page 7: Photography: 2 - Lens Sizes and Depth of Field

A zoom lens is a jack of all trades lens that can change its length from, say, 30mm to 70mm:

Page 8: Photography: 2 - Lens Sizes and Depth of Field

Many digital cameras do not have a CCD sensor that is as big as a 35mm film frame so some cropping occurs

GEEKGEEKALERTALERT!!

Page 9: Photography: 2 - Lens Sizes and Depth of Field
Page 10: Photography: 2 - Lens Sizes and Depth of Field

Depth of Field (DOF) refers to how much of a photo is in focus

Suppose you have focused on a person you want to photo:

Page 11: Photography: 2 - Lens Sizes and Depth of Field

The DOF is the distance you could move the object towards or away from the camera without having to re-focus:

Page 12: Photography: 2 - Lens Sizes and Depth of Field

Everything outside of this zone will be blurred and out of focus

Page 13: Photography: 2 - Lens Sizes and Depth of Field

>>> DEMO <<<

>>>DOF with zoom lens<<<

Page 14: Photography: 2 - Lens Sizes and Depth of Field

There are three (four counting Photoshop) ways to create shallow Depth of Field:

1.Use a long (70mm+) lens or a zoom2.Set a smaller aperture setting (f2.8 / f4)3.Put a Neutral Density filter on your lens

Page 15: Photography: 2 - Lens Sizes and Depth of Field

There are various setting on an SLR camera:

ISO Shutter Speed Aperture

They all adjust different aspects of your photo…

Page 16: Photography: 2 - Lens Sizes and Depth of Field

Aperture adjusts the Depth of Field by changing the size of the hole that light travels through to get to your film/CCD:

Page 17: Photography: 2 - Lens Sizes and Depth of Field

Basically, the smaller you set the f number to, the smaller your Depth of Field:

Page 18: Photography: 2 - Lens Sizes and Depth of Field
Page 19: Photography: 2 - Lens Sizes and Depth of Field

Changing the aperture means changing the shutter speed to compensate (more next week), for now…

Set your camera to aperture priority mode (usually marked ‘A’ or ‘Av’on the control dial)

Page 20: Photography: 2 - Lens Sizes and Depth of Field

Narrow DOF

Wide DOF

Page 21: Photography: 2 - Lens Sizes and Depth of Field

>>> TASK <<<

Put an a few objects on along a table Step back as far as you can and zoom in to create DOF Then get closer and take two identical photos – one on f2.8

and one on f16

If you don’t have these setting on your camera try using Macro mode and getting really in close…

…and/or take some photos that you can add DOF to later using Photoshop

Page 22: Photography: 2 - Lens Sizes and Depth of Field

On a bright summer’s day you will have to set your aperture to a high number (f11 / f16) to avoid over exposure…

So setting a small f-number toget a small Depth of Fieldwill not work

The solution is to put aNeutral Density filter on yourcamera…

Page 23: Photography: 2 - Lens Sizes and Depth of Field

Using an ND filter is a bit like putting sunglasses on your camera

Page 24: Photography: 2 - Lens Sizes and Depth of Field

What this means is that you can open the aperture a bit more and get more Depth of Field

ND filters do not effect the colour, only the amount of light reaching the film/CCD

Page 25: Photography: 2 - Lens Sizes and Depth of Field

And, of course, Depth of Field can be faked using Photoshop selections and a blur filter:

Page 26: Photography: 2 - Lens Sizes and Depth of Field

>>> END <<<