Understanding depth of field: try it yourself

This practical is written so that somebody doing it for the first time can follow it without guessing. Read one exercise, do it, compare the result, then move to the next. Keep the lesson open beside you if you need it.

Before you begin

• Charge the battery or make sure the phone has enough power.
• Check that a memory card is fitted where your camera needs one and that you have space for the photographs.
• Use a safe, stationary subject unless the exercise specifically calls for movement.
• Keep the camera position and subject as consistent as possible when comparing settings.
• Do not force a control, card, battery, lens or door. If something does not fit or move easily, stop and check the manual.

1. Three-Object Row

Place 3 toys in a line—focus on middle one at f/3.5 vs. f/11.

Set up the subject first and make a starting photograph before changing anything. Check that the camera has focused where you intended. Make the change described in the exercise, take the comparison photograph, then review both at the same magnification.

Look specifically for the effect the exercise is testing. Ignore whether the subject is artistic. If you cannot see a difference, exaggerate the change, repeat the pair and make sure no other important setting or part of the scene changed at the same time.

2. Foreground Blur

Hold a leaf or lace in front of your lens—shoot a subject behind it.

Set up the subject first and make a starting photograph before changing anything. Check that the camera has focused where you intended. Make the change described in the exercise, take the comparison photograph, then review both at the same magnification.

Look specifically for the effect the exercise is testing. Ignore whether the subject is artistic. If you cannot see a difference, exaggerate the change, repeat the pair and make sure no other important setting or part of the scene changed at the same time.

3. Distance Test

Focus on a book 1ft away, then 5ft away—same aperture—note DoF change.

Set up the subject first and make a starting photograph before changing anything. Check that the camera has focused where you intended. Make the change described in the exercise, take the comparison photograph, then review both at the same magnification.

Look specifically for the effect the exercise is testing. Ignore whether the subject is artistic. If you cannot see a difference, exaggerate the change, repeat the pair and make sure no other important setting or part of the scene changed at the same time.

4. Portrait DoF

Shoot face at f/2.8 (blurry background) vs. f/8 (sharper background).

Set up the subject first and make a starting photograph before changing anything. Check that the camera has focused where you intended. Make the change described in the exercise, take the comparison photograph, then review both at the same magnification.

Look specifically for the effect the exercise is testing. Ignore whether the subject is artistic. If you cannot see a difference, exaggerate the change, repeat the pair and make sure no other important setting or part of the scene changed at the same time.

5. Smartphone Sim

Use portrait mode, then turn it off—compare background blur.

Set up the subject first and make a starting photograph before changing anything. Check that the camera has focused where you intended. Make the change described in the exercise, take the comparison photograph, then review both at the same magnification.

Look specifically for the effect the exercise is testing. Ignore whether the subject is artistic. If you cannot see a difference, exaggerate the change, repeat the pair and make sure no other important setting or part of the scene changed at the same time.

Troubleshooting

If nothing happens, check the shooting mode first. Automatic modes can prevent manual changes. If the photograph is blurred, decide whether the camera moved, the subject moved or focus landed in the wrong place. If it is unexpectedly bright or dark, check exposure compensation and ISO as well as the setting being tested. Change one thing and try again.

You are finished when

• You have completed the comparisons rather than simply reading the instructions.
• You can point to the photographs and identify the visible difference.
• You can explain which change caused that difference.
• You know what you would try if the same situation occurred again.