Tuesday Assignment #2 – Adjusting Depth Of Field With Distance – 31+ Days To Better Photography

In the last Tuesday Assignment I introduced a rather simple test to show the difference in depth of field with adjustments made to Aperture. If you tried that assignment, you found that, as aperture get smaller (the number gets higher) then the amount of objects in a scene that are in focus typically gets higher. To a physical limiting point.

As a rule of thumb: The larger the aperture number, the larger the number of things that can be in focus.

Now let’s take this setup one step further, because depth of field is also affected by where you are.

Let’s use the same setup:

If you forget about the last assignment, run it again.

These next steps are fairly simple but they are important for those getting started in understanding depth of field. Some parameters:

  1. Make sure your camera is in Aperture Mode (A or Av on the big dial). Set your ISO to 400 and make sure this scene is well lit. Make sure the light source is mostly to the side or behind the camera. Having a light source in front will make things harder to see.
  2. Set the Aperture to the lowest number you can achieve. This may be f/1.8 or f/3.5 or some such.
  3. Set your focal length to 50mm if you have a zoom. Or choose a lens close to 50mm if you only have prime (non-zooming) lenses.
  4. Take the shot at 18″/.45m away from the Organic Tasty-Yummy-Os as before <CLICK>. Make sure, in all these cases, you maintain focus on the box and not the motoroil. You may need to switch to manual focus.
  5. Now take one full step backward. Don’t change zoom. Don’t change Aperture or ISO (and don’t worry about Shutter Speed too much, unless it will cause blur).
  6. Change your focus so it is tight on the box of Os again. That box will look smaller and that’s ok, but focus on it any way.
  7. Take a photo. <CLICK>
  8. Now take one more step back and repeat step 6.
  9. Take a photo. <CLICK>
  10. Lastly, I want you to get as close as your lens will focus to the box. This may be 12″ or less. Again, focus on the box without changing settings.
  11. Take a photo. <CLICK>

You’re done!  Now to examine the four photos you just shot.

Some critical questions to ask yourself:

  • While viewing the images on a computer, between shots 1, 2 and 3, what happened to the focus on the motoroil?
  • How is shot 4 different than shot 1?
  • How big of a difference is there, in the focus on the motoroil, from shot 4 to shot 3?
  • In all four shots, how much does the box of Os stand out compared to the rest of the scene?
  • Which shot is most striking to you?

Remember, you changed nothing in this experiment except your location. Focus was still maintained on the box. So what changed when you moved? How do the images compare?

With some of those results in mind,  switch to a medium number for aperture, like f/8 or f/11 (higher number) than the first set of shots and repeat. What do you expect to result?  Will more things, or less things, be in focus at the same physical distance?

These two experiments will help you understand how depth of field is affected by location and a how aperture also plays a part. Those are two of the three ways you can change depth of field and next Tuesday we will cover #3.

Let me know if you have any questions while experimenting.

31 Days To Better Photography is a series written by professional photographer Peter West Carey on The Carey Adventures.Com. The series is designed to unravel the mysteries of photography so you can take better pictures. Subscribe here to receive all the updates, and bonus material. Your comments are always welcome.

3 Replies to “Tuesday Assignment #2 – Adjusting Depth Of Field With Distance – 31+ Days To Better Photography”

  1. monstermum

    When I changed to f11 the subject matter appeared larger. I had my tripod in the same places. Was this supposed to happen?
    (using Canon EFS 18-200 mm lens set on 50 mm)


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