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Kevin is here, Wayne is back from Norway, and the Shutter Brothers are together again and ready to take a deep dive into everything about depth of field - what is it, how can it be controlled, and why it matters. Learning how to make depth of field work for you can take your photography to a higher level, and that's a good thing! (You can find Wayne's notes on depth of field below.)
Wayne also shares his recent experiences in Norway and the approach to photography he took while there. He had many memerable experiences along the way, including a visit to a truly awesome analog photogrpahy shop in Bergen (where Wayne was able to replenish his film supply). He used all three of the cameras he brought wih him, and he shot mmost of his film. We can't wait to see the results!
Finally, the Shutter Bros read some interesting listener email from a couple of Mikes, one of which may have an impact on Kevin's Condo Bathroom Darkroom Project.
1. What is DOF?
Basically, it’s the distance between the closest and farthest points that are in “acceptably” sharp focus, kind of a “zone” of sharpness.
What is “acceptably” sharp?
A point focused on the film is considered sharp as long as it is perceived as a point. As you focus in front of or behind a point, that point becomes a small blurry disc. When the size of that blurry disc, known as the circle of confusion, becomes perceptively larger than a point it’s no longer considered “sharp”. The size of an acceptable circle of confusion has been standardized and varies with film format. Sharpness is also measured in terms of line pairs per millimeter (lp/mm).
|
Negative Format |
24x36 |
6x4.5 |
6x6 |
6x9 |
4x5 |
|
Circle of Confusion (mm) |
0.022 |
0.039 |
0.042 |
0.052 |
0.089 |
|
Min Negative Resolution (lp/mm) |
45 |
26 |
24 |
19 |
11 |
These numbers assume a minimum viewing distance equal to the diagonal of a full frame print.
|
Print Size (inches) |
4x6 |
5x7 |
8x10 |
11x14 |
16x20 |
|
Viewing Distance (inches) |
7.2 |
8.6 |
12.8 |
17.8 |
25.6 |
2. How to control DOF?
(1) f/stop: The depth of field doubles if the f/number is doubled. For example going from f/8 to f/16 will double the depth of field.
(2) Focal length of the lens: Depth of field is inversely proportional to the square of the focal length. Reducing the focal length by one half will increase the depth of field four times.
(3) Distance to the subject: Depth of field is proportional to the square of the distance. Doubling the distance to the subject will increase depth of field by four times, triple the distance, the depth of field increases nine times.
(4) Amount of enlargement and viewing distance.
(5) Use of view camera movements or a tilt/shift lens can alter the plane of focus.
(6) Use neutral density filter if you’re after shallow depth of field.
3. How to know actual DOF?
(1) Depth of field scale on the lens.
(2) Depth of field preview, if your camera has it.
(3) Web sites and phone apps.
(4) Spend some time with a good web site or phone app and make yourself a chart.
(5) Many old Kodak photo data guides had depth of field calculators.
4. Tips on focusing and subject placement.
(1) Position camera to place important elements the same distance from the camera.
(2) Focus on closest point you want in focus and check distance on focusing scale. Repeat for farthest distance and either use the depth of field scale, app, chart, or calculator to place those distances on the extremes of whatever f/stop they fit.
(3) Focus 1/3 of the way between the near and far points and stop down as much as you can.
(4) If you’re going after shallow depth of field, use a long lens and use the smallest f/stop you can. Use a neutral density filter if you have to.
(5) Use the hyperfocal distance.
5. What is hyperfocal distance and how is it used?
Hyperfocal distance is the near limit of the depth of field, for a given lens focal length and f/stop, with the lens focused on infinity. If you refocus the lens to that distance, the depth of field extends from half that distance to infinity. This is especially useful for scale focusing cameras.
