DOF Calculation & Crop Factor & Resolution

[dsze]

Spent some of the rainy morning today trying to become more familiar with common DOF's and I have a couple of questions.

1. When calc. DOF on my 10D I, should be using the 1.6X for the focal Length and NOT what is written on my lens (the 35mm equivelent)...correct?

2. What resolution should I be seeking on my 10D for this calculation? 67.665 lines/mm? more? less?

-based on the calculation: 1536pixels/22.7mm=67.665

I'm trying to set up a DOF program on my PDA. :wink: For those boring meetings/inservices; might as well be learning some photog. stuff right?

thanks for any advice!
-daniel

[Scottes]

1) No. You should be using the actual length, and a CoC of 0.019

[dsze]

By actual length, you mean the focal length, not the distance to the subject right? And why not factor in the 1.6X? I'm just curious.

thanks,
daniel

[amorrison]

Here is a simple spreadsheet I built to do DOF for a 20D. Maybe you could adapt it to a PDA.

http://agmorrison.com/pics/lens_DOF.xls

[Scottes]

Yes, the actual focal length of the lens. The CoC is based on the the sensor size and thus incorporates the crop factor. Also, calculations should be based on the distance from the sensor, not from the end of the lens.

[dsze]

very nice spreadsheet amorrison!

-daniel

[Jesper]

Here is a DOF calculator for your PDA: DOFMaster (http://www.dofmaster.com/)

The equations for calculating depth of field are given here: http://www.dofmaster.com/equations.html]the equations. You should not multiply the focal length with 1.6. The thing that changes for different cameras is the circle of confusion (c in the equations).

Also have a look at the articles on that website, there's a lot of information about DOF there.

[dsze]

Jesper, thanks. That one looks good because it already includes digital as one of the format choices. The PDA version appears to only be for PalmOS though. I've got a PocketPC. :(

-daniel

[Jon]

Jonathan Sachs has one for the Pocket PC. Google for him, or for his "Ephemeris" program (for sunrise/sunset/moonrise/moonset/phase of moon) to find it.

[dsze]

Yes, I have the Sachs one, but he's the one who suggests using the 1.6X crop factor.

-daniel