 John Tomley |
Minimum Depth od Field Hi, Is there any way of determining the minimum depth of field one can achieve given the choice of lens, f stop and selective focusing. Example- 100-300 zoom lens set at 300mm, F5.6 and focused on an object at 10 feet from the lens.Can the near and far distances be determined in advance without carrying a palm pilot with software installed. Thanks
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Jon Close |
Yes, but the palm pilot isn't a bad solution. The design of most autofocus lenses makes it impractical to imprint a depth of field scale on the barrel. But I've downloaded a nifty freeware PC program called DOFMaster (link) that allows you to print simple scales for use in the field. The link also has download for displaying the scales on a Palm Pilot.
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John P. Sandstedt |
Check you manufacturer's specs. You should have received a depth of field chart with the lens. Call or e-mail your lens's manufacturer or, go to the library. Depth of field is a mathematical [optical] property and isn't specific to a particular lens. Rather, there are simple equations in many photography that allow DOF to calculated based on aperture, distance to subject and lens focal length. Of course, now we have these new-fangled zoom lenses. SO look for "older books like Aaron Susmann's Handbook of Photography 1973 or Andreas Feininger's Complete Photographer. Or, go to almost any one of John Hedgecoe's or Michael Freeman's Photography Handbooks. There you'll fine DOF tables.
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John Tomley |
Hi to both Jon and John Thanks for the replies. I have downloaded the software for printing out the DOF scales and will make up the circular calculator as shown. I will try to get hold of the books that John has suggested and read up on what they say. I've experimented with the lenses I have (All second hand and no DOF charts) and if I can ask another question it is - Does moving closer to the subject and shortening the focal length have any better or worse effect than using a longer focal length lens. Assume that the subject fill the viewfinder at the same scale.
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Jon Close |
If you change both the focal length and the subject distance such that the subject is rendered the same size, but keep the aperture unchanged then DoF is the same. For example, at f/8, a 200mm lens focused to 10 feet, 100mm lens focused to 5 feet, and 50mm lens focused to 2.5 feet all give give the same magnification of 0.07x, and all give DoF from 1 5/8" in front to 1 3/4" behind the focused distance. If you change focal length and focus distance such that magnification is increased, then DoF is decreased, and vice versa. Another nifty freeware program I used for that example is f/Calc from http://www.tangentsoft.net/.
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Doug Elliott |
John, What are you trying to photograph? I just did a High School Senior's ring. I used a 105mm lens and shot at 2 seconds at f/16. I also shot it at f/8 the differece was about 1 inch. At f/8 the engraved mascot was out of focus. At f/16 the jewel in the front it's internal start bust and the mascot were in sharp focus. It was 85% of the frame because I wanted to use it in a collage of the senior. I did some reseach and here is the formula for DOF. Here is the math stuff for your review. Note 1: Based on acceptable sharpness for an 8x10 inch print. Note 2: Multiply Inches by 25.4 to convert to Millimeters. Divide Millimeters by 25.4 to convert to Inches. Hyperfocal Distance
Far Focus Limit
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John Tomley |
Thanks on c for the info. To Doug - I am trying to pre determine the amount of depth of field I can achieve rather than say use 5.6 (The largest apeture I have on the 300 mm zoom lens) and take what I get. I would like to know, perhaps using a table, the DOF at F5.6 and F8.0given the same settings for focal length and distance to object. Did you know in advance that the difference in DOF was 1 inch orthats what it turned out to be.
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