Depth of Field in the field

[Don Wallace]

What is a practical and simple way to calculate dof in the field? I do a lot of "people" photography (not just portraits) outdoors and bring a set of homemade plasticized dof tables with me to cover most situations. Is there a handheld calculator I can buy that allows me to get fairly precise dof answers? From what part of the lens do I measure?

Finally, are there any good primers on how to use dof effectively in real situations? I really don't want tons of math - just some basic info on "how to get that rock in the foreground in focus and the trees in the near distance out of focus."

[Bob Salomon]

Rodenstock makes a handheld calculator with DOF for all format from 35mm to 810 in level and inclined positions at several image ratios. The other side calculates Scheimpflug. Easily fits in a shirt pocket and has a mm scale ruler to measure the displacements between the near and far point on the gg and on the rail/bed.

[jose angel]

I run Vademecum on a Palm device. All the calculations you can imagine. I found this combo the best I have seen ever. Precise and relatively fast to use.

[Walt Calahan]

Jose, do you have the URL of the Palm calculator "Vademecum" that you can share with us. I Googled Vademecum and got toothpaste in Europe. HA!

Thanks in advance.

[Denis Pleic]

Walt, the software is Bob Wheeler's:

http://www.bobwheeler.com/photo/Software/software.html

Denis

[Dan Jolicoeur]

D(mm) F

1--------16.6

2--------22.6

3--------32.2

4--------32.6

5--------32.9

6--------45.2

7--------45.4

8--------45.6

9--------45.8

10-------64

http://www.largeformatphotography.info/fstop.html

I have this chart taped to my ground glass protector taken from the above link on the front page of this forum.

I simply measure the Delta distance moved between the near and far focus, doesn't matter where you measure it, camera bed movement or calculated turns of a knob.

You may find it usefull to read the front page of this forum titled articles under "Taking the Picture"

Regards, Dan

[Leonard Evens]

The easiest way to estimate dof in the field is to use the so-called focus spread method. This is described in detail elsewhere on the large format webpage. What you do is focus on the nearest point you want in focus, note the position along the rail (or bed), then focus on the furthest point and do the same. The distance along the rail between those points is the focus spread. You then place the standard halfway in between and determine the needed F-stop based on the focus spread. Paul Hansma has suggested a method of balancing defocus and diffraction which yields the table that Dan gave above. I find that to be too conservative. Another rule which ignores diffraction says to multiply the focus spread by 10 and then divide the result by 2 to determine the F-number. I find that the best choice is somewhere between these two extremes.

A variation of this method due to Steve Simmons doesn't require any numbers at all. Focus so that the nearest and furthest points you want to be in focus appear on the gg to be equally out of focus. Then, using a loupe, stop down until those points come into focus. This works quite well if you don't have to stop down too far, but few of us can make out anything on the gg at apertures smaller than f/16 or f/22. It also can be used as a backup for the focus spread method.

In using the focus spread method, it helps to have a distance scale on your focusing knob. It is not too hard to put such a scale on your focusing knob. I describe how I did it for my Toho FC-45X at www.math.northwestern.edu/photos/pages/dofessay.pdf. Some Sinars have a scale marked in F-numbers on the focusing knob, and there is an alternate method based on the same ideas I've described here which you can use with it. The large format webpage has a description of how to make a Sinar type scale of your own, and how to use it.

[Graeme Hird]

"What is a practical and simple way to calculate dof in the field?

Use a loupe on your ground glass and set the aperture appropriately. DoF with LF gear is an esoteric concept in any case.

Cheers,

[Dan Jolicoeur]

DoF with LF gear is an esoteric concept in any case.

Hence the Category: Beginner's Questions.

What is wrong with expanding the inner circle?

[paulr]

"Paul Hansma has suggested a method of balancing defocus and diffraction which yields the table that Dan gave above. I find that to be too conservative."

just intuitively, those numbers look incredibly conservative to me. i'm guessing i'd be shooting most of my pictures at f64 if i followed that, but i rarely go below f22 or f32.

has anyone else actually experimented with this kind of thing?