DOF charts

[xkaes]

Anyone ever use what I call a DOF chart? Here's one of mine:



I have one for each of my lenses. (FYI, I print them out in B&W on 8.5 X 11 paper, so they appear basically reversed from the above picture. PLUS, the positioning of the f-stops is messed up in this transfer to JPEG format.) I use them to determine what will REALLY be in focus. Sure, I have a nice, adjustable 7X Wista loupe for the groundglass, but a DOF chart with a rangefinder is more accurate.

I use an Ideal Rangefinder which is very small and light.



Other companies have made them as well, from Kodak to Leica. They can be purchased for next to nothing -- well, maybe not the Leicas. My Ideal model focuses from 2.5 feet to infinity, an is adjustable should that be necessary. No battery needed. For closer focusing, I use a tape measure.

I have never seen DOF graphs available commercial, but perhaps I have not looked hard enough because I made my own. I started with a circle of confusion of my choice and wrote a program for each lens in Turbo Pascal and then plotted the results in Harvard Graphics on logarthmic distance scales. On the scene, I choose the near and far points that I want in acceptable focus. Then I use the rangefinder to determine their exact distance from the film. I then check the DOF chart to determine what the f-stop needs to be to achieve that -- without any tilts or swings. But tilting and swinging is always an option if I need to use them, but I'll still place my focusing in the center of the range -- again with the help of the rangefinder.

[ic-racer]

Many large format photographers use some mechanism to determine the focus spread on the focusing standard. This allows calculation of the optimum aperture based on both Airy disks and CoC.

[Bob Salomon]

Anyone ever use what I call a DOF chart? Here's one of mine:



I have one for each of my lenses. (FYI, I print them out in B&W on 8.5 X 11 paper, so they appear basically reversed from the above picture. PLUS, the positioning of the f-stops is messed up in this transfer to JPEG format.) I use them to determine what will REALLY be in focus. Sure, I have a nice, adjustable 7X Wista loupe for the groundglass, but a DOF chart with a rangefinder is more accurate.

I use an Ideal Rangefinder which is very small and light.



Other companies have made them as well, from Kodak to Leica. They can be purchased for next to nothing -- well, maybe not the Leicas. My Ideal model focuses from 2.5 feet to infinity, an is adjustable should that be necessary. No battery needed. For closer focusing, I use a tape measure.

I have never seen DOF graphs available commercial, but perhaps I have not looked hard enough because I made my own. I started with a circle of confusion of my choice and wrote a program for each lens in Turbo Pascal and then plotted the results in Harvard Graphics on logarthmic distance scales. On the scene, I choose the near and far points that I want in acceptable focus. Then I use the rangefinder to determine their exact distance from the film. I then check the DOF chart to determine what the f-stop needs to be to achieve that -- without any tilts or swings. But tilting and swinging is always an option if I need to use them, but I'll still place my focusing in the center of the range -- again with the help of the rangefinder.

You can download a DoF chart for 45 to 810 from the Linhof web site. You can buy a dof and scheimpflug pocket calculator for all formats from 35 to 810 at all ratios from 1:1 to infinity from Rodenstock. It uses no power, other then your fingers and fits in your shirt pocket.

[goamules]

There was a guy the other day that was trying to tell me the DOF varies for different lenses that have the same focal length and aperture. I thought that was optically impossible, that DOF is only based on FL and aperture. Am I wrong?

[Randy]

There was a guy the other day that was trying to tell me the DOF varies for different lenses that have the same focal length and aperture. I thought that was optically impossible, that DOF is only based on FL and aperture. Am I wrong?

I have wondered the same thing but never tried to find the answer.

[jp]

There was a guy the other day that was trying to tell me the DOF varies for different lenses that have the same focal length and aperture. I thought that was optically impossible, that DOF is only based on FL and aperture. Am I wrong?

I think normal lenses will behave according to the chart.

Soft focus lenses with spherical aberration will have increased DOF compared to a sharp lens.. Due to the layered focusing

Lenses with altered correction for SA will have DOF that does not conform to the usual ratios of front and back DOF, like the Nikon 105DC with it's DC dial.

[xkaes]

Are you talking about this? I see nothing about focal length nor DOF.

[goamules]

Thanks for the fast dialog on my question. Yeah, this was on the Rangefinder forum, where they wax eloquently about intangibles like "3D look" of Leica lenses. The OP was asking "what Leica best shows the 3D look they're famous for." I answered something along the lines of "um...I've never really seen a 3d shot, outside of a 3D movie theatre and wearing glasses. Those that call something 3D are just being subjective, others don't see it." My statement was that all lenses will look the same for depth of field, if at the same aperture/FL. And that some aberrations are all that is different, but they don't really create "3D." When I proposed some experiments with 2 different lenses, shot identically to determine which was "more 3D", I was soundly beaten to pulp...

[xkaes]

It's not just focal length and aperture. Before that is the circle of confusion. The FL and f-stop are pretty well defined, but the circle of confusion is a choice, an opinion. What one person or company considers acceptable, another won't. That's why one company's DOF tables will differ from another company's, even when the FL and f-stop are the same. The larger the circle of confusion that you consider acceptable, the wider the DOF will be.

[Bob Salomon]

Of course you don't. You tell it the near point on your rail extension and the far point. You then tell it the image ratio you want and the tilt of your camera to the subject. It will then tell you where to place the back, the required aperature and any needed exposure correction.