Aperture, Distance, and Focal Length

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for DSLRs
This rather messy set of images attempts to play with three inter-dependent variables: f-stop, focal length, and distance. Most pages in this site play with a single variable but this page admits that you can NOT think about depth of field without considering f-stop, AND focal length AND distance to the subject. Easy answers are so attractive — no wonder people fall for them so often.

We used the keyboard setup so we could use both Nicole's front and back hands and the keyboard keys as a measure of depth of field. HOWEVER: we cheated — we HAD to have Nicole move her hands to different places for the 400mm vs 16mm shots. The vastly different angles of view from 400 to 16 were too great to be rigid in the setup. Rats.

Bottom Line: Depth of field depends on three factors: aperture, distance to subject, and focal length.

400mm f5.6
400mm f32
400mm f5.6
400mm f32
16mm f2.8
16mm f22
16mm f2.8
16mm f22
400mm f5.6
400mm f32
400mm f5.6
400mm f32
16mm f2.8
16mm f22
16mm f2.8
16mm f22
400mm f5.6
400mm f32
400mm f5.6
400mm f32
16mm f2.8
16mm f22
16mm f2.8
16mm f22
Left
Right

A 400mm lens at f5.6 — its widest aperture — produces a very narrow depth of field at 4 feet. Compare to a 16mm lens at f2.8 — its widest aperture — shot at only about 2 feet from Nicole in panel 4.

You barely get a single key in focus here, compared to what you get with smaller f-stop in panel 2, or more distance in panel 3.

The depth of field calculator says:
Near focus limit = 48 in
Far focus limit = 48 in
Total depth of field = 0.08 in (almost NONE)

This is the image with the narrowest depth of field of all 8 panels.

This 400mm lens at 4 feet at f22 produces much more depth of field than at f5.6, to the left, but much less than the same lens at 16 feet, seen in the 3rd panel.

Here you get about 5 black keys in focus, but neither hand.

The depth of field calculator says:
Near focus limit = 47.8 in
Far focus limit = 48.2 in
Total depth of field = 0.17 in (less than a quarter inch!)

This 400mm lens at f5.6 produces a very different depth of field at 16 feet from the subject than at 4 feet, as shown in the panel to the left.

At this distance we also get about 5 black keys in focus, but still neither hand.

The depth of field calculator says:
Near focus limit = 15.9 ft
Far focus limit = 16.1 ft
Total depth of field = 0.15 in (more than at 48 inches, but not much)

Here the 400mm lens at 16 feet from Nicole at f22  produces much more depth of field than the same setup at 4 feet in panel 2. We get almost the whole keyboard in focus, and nearly both her front and back hands.

The depth of field calculator says:
Near focus limit = 15.7 ft
Far focus limit = 16.3 ft
Total depth of field = 0.61ft (still not much)

At 16mm at f2.8 and about two feet from Nicole, we get many keys in focus, but not quite her front or back hand. (Note we had to move her hands to get the shot to work at all.)

The depth of field calculator says:
Near focus limit = 1.67 ft
Far focus limit = 2.49 ft
Total depth of field = 0.82 ft (quite a bit)

I also had to crop this image to make it comparable to the others. Below is the uncropped image:

uncropped 16mm

Then at 16mm at f22 and about 2 feet from Nicole, we get almost the whole keyboard and both hands which are toward the ends of the keyboard.

The depth of field calculator says:
Near focus limit = .78 ft
Far focus limit = infinite
Total depth of field = infinite (!)

Here we are about 6 feet from Nicole at 16mm and f 2.8. Even at this wide aperture we get almost the whole keyboard, up to her hands, in focus.

The depth of field calculator says:
Near focus limit = 3.75 ft
Far focus limit = 15 ft
Total depth of field = 11.3 ft (!)

This image also needs some cropping to make it easier to compare. Below is the uncropped version:
uncropped 16mm at 6 feet

But at 6 feet away and at f22 almost everything is in focus — but NOT the curtain behind Nicole. Since we set our critical focus point to be in between her near hand and her face, the background curtain is a bit soft.

The depth of field calculator says:
Near focus limit = 1.03 ft
Far focus limit = infinite
Total depth of field = infinite (!)

(We did not get infinite far focus because we focused not on Nicole's face at 6 feet, but closer to her front hand.)

This is the image with the MOST depth of field of all 8 panels.

A 400mm lens at f5.6 — its widest aperture — produces a very narrow depth of field at 4 feet. Compare to a 16mm lens at f2.8 — its widest aperture — shot at only about 2 feet from Nicole in panel 4.

You barely get a single key in focus here, compared to what you get with smaller f-stop in panel 2, or more distance in panel 3.

The depth of field calculator says:
Near focus limit = 48 in
Far focus limit = 48 in
Total depth of field = 0.08 in (almost NONE)

This is the image with the narrowest depth of field of all 8 panels.

This 400mm lens at 4 feet at f22 produces much more depth of field than at f5.6, to the left, but much less than the same lens at 16 feet, seen in the 3rd panel.

Here you get about 5 black keys in focus, but neither hand.

The depth of field calculator says:
Near focus limit = 47.8 in
Far focus limit = 48.2 in
Total depth of field = 0.17 in (less than a quarter inch!)

This 400mm lens at f5.6 produces a very different depth of field at 16 feet from the subject than at 4 feet, as shown in the panel to the left.

At this distance we also get about 5 black keys in focus, but still neither hand.

The depth of field calculator says:
Near focus limit = 15.9 ft
Far focus limit = 16.1 ft
Total depth of field = 0.15 in (more than at 48 inches, but not much)

Here the 400mm lens at 16 feet from Nicole at f22  produces much more depth of field than the same setup at 4 feet in panel 2. We get almost the whole keyboard in focus, and nearly both her front and back hands.

The depth of field calculator says:
Near focus limit = 15.7 ft
Far focus limit = 16.3 ft
Total depth of field = 0.61ft (still not much)

At 16mm at f2.8 and about two feet from Nicole, we get many keys in focus, but not quite her front or back hand. (Note we had to move her hands to get the shot to work at all.)

The depth of field calculator says:
Near focus limit = 1.67 ft
Far focus limit = 2.49 ft
Total depth of field = 0.82 ft (quite a bit)

I also had to crop this image to make it comparable to the others. Below is the uncropped image:

uncropped 16mm

Then at 16mm at f22 and about 2 feet from Nicole, we get almost the whole keyboard and both hands which are toward the ends of the keyboard.

The depth of field calculator says:
Near focus limit = .78 ft
Far focus limit = infinite
Total depth of field = infinite (!)

Here we are about 6 feet from Nicole at 16mm and f 2.8. Even at this wide aperture we get almost the whole keyboard, up to her hands, in focus.

The depth of field calculator says:
Near focus limit = 3.75 ft
Far focus limit = 15 ft
Total depth of field = 11.3 ft (!)

This image also needs some cropping to make it easier to compare. Below is the uncropped version:
uncropped 16mm at 6 feet

But at 6 feet away and at f22 almost everything is in focus — but NOT the curtain behind Nicole. Since we set our critical focus point to be in between her near hand and her face, the background curtain is a bit soft.

The depth of field calculator says:
Near focus limit = 1.03 ft
Far focus limit = infinite
Total depth of field = infinite (!)

(We did not get infinite far focus because we focused not on Nicole's face at 6 feet, but closer to her front hand.)

This is the image with the MOST depth of field of all 8 panels.