1. Lens sizes Depth of Field
Focal Lengths
Lens sizes
Depth of Field

2. Lens Sizes
Camera lenses come in different sizes:

3. Lens Sizes
The longer the lens the more it enlarges the object being photographed

4. Lens Sizes Lens are measured in mm…
50mm is roughly the same as what we see with the human eye:

5. Lens Sizes
Less than 50mm (typically 24-30mm) gives wide angles:

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

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

8. Crop Factor
GEEK
ALERT!
Many digital cameras do not have a CCD sensor that is as big as a 35mm film frame so some cropping occurs

9. Depth of Field

10. 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:

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

12. Depth of Field
Everything outside of this zone will be blurred and out of focus

13. Depth of Field
>>> DEMO <<< >>>DOF with zoom lens<<<

14. Depth of Field
There are three (four counting Photoshop) ways to create shallow Depth of Field:
Use a long (70mm+) lens or a zoom
Set a smaller aperture setting (f2.8 / f4)
Put a Neutral Density filter on your lens

15. Aperture Settings There are various setting on an SLR camera: ISO
Shutter Speed
Aperture
They all adjust different aspects of your photo…

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

17. Aperture Settings
Basically, the smaller you set the f number to, the smaller your Depth of Field:

18. Aperture Settings

19. Aperture Settings
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)

20. Compact Cameras & Phones
Narrow DOF
Wide DOF

21. >>> TASK <<<
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

22. And Finally… ND Filters
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 to get a small Depth of Field will not work
The solution is to put a Neutral Density filter on your camera…

23. Neutral Density Filters
Using an ND filter is a bit like putting sunglasses on your camera

24. Neutral Density Filters
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

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

26. >>> END <<<