Is there a table anywhere that gives the minimum value for DOF when focusing on infinity at specific apertures?

EG. my 35mm f/1.4 might keep everything from 5m to infinity in focus at F2. This could save my butt when it gets dark...

Where could I find this info?

Search these forums. Jonathan has a spreadsheet (I think it is his) and there should be a link to a webpage that does the same.

You have to know how big you want to print and how close you plan of viewing the print to make a decision about DOF.

If you want to make 4x6 prints, yes f/2 is enough to get good DOF. For a bigger print, maybe f/2 isn't enough.

A DOF chart probably wont give you a completely accurate answer, unless you factor all these things into account.

An easy option might be to try a test shot in daylight conditions at varying apertures, and see which aperture gives you enough DOF for your purposes.

Dof master?
http://www.dofmaster.com/dofjs.html

Jonathan's is here.
DoFMaster uses the traditional criteria while Jonathan's uses pixel pitch as the CoC.


As Sheldon says, you need to know print size and intended viewing distance and digital has had an impact on how folks crop/uprez/downrez/print etc, so if precise DoF control is critical to your aims, you need to study, not just consult a table

Andy

Try this: DOF Calcuator (Cambridge in Color).

Note that many standard tables for DOF are rather lax, and if you have 20/20 vision and view the prints at normal distance, the DOF decreases dramatically.

Bill

http://www.visual-vacations.com/Photograph...calculation.htm

When Jonathan says vertical height of sensor, which direction is that...does he mean the height when holding the camera in the traditional hand-held orientation?

The smallest dimension of the sensor, in pixels and millimeters.

DoF calculators do not take lens quality factors into consideration. My experience is that many lenses are quite poor at very wide apertures of F2 and wider.

I don't know how the Canon 35/1.4 rates at F2, but at F1.4 it seems worse than the cheapest lens (at f8) that money can buy. At 10 lp/mm the MTF graph never rises above 80% and at 40 lp/mm never rises above 40%.

The usual counter argument is, you don't use wide apertures to get crisp resolution but to get shallow DoF.

My argument would be, if you haven't got crisp resolution at the plane of focus, you haven't got the shallow DoF that the DoF calculators would imply.

To take an extreme analogy, pin-hole cameras produce great DoF, but the images are not sharp anywhere.

Perhaps I should add, I've excluding esthetic considerations from the above comment, such as niceness of bokeh.

Another consideration, if you are trying to get good DoF (as opposed to shallow DoF) at wide apertures, is resolution fall-off near the edges. Wide angle lenses are particularly susceptible to this at wide apertures.

When attempting to get a shallow DoF, performance at the edges is usually not a concern. But focussing at infinity, or close to infinity, with the purpose of achieving maximum DoF, I imagine that performance at and near the edges would be a concern. So basically, at F2, you could expect below par resolution at the plane of focus and very much below par resolution near the edges. Sound enticing?

thx. as I look back at the question, I was over-thinking the issue and the answer is obvious.