# dof calculator

Started Feb 25, 2013 | Discussions thread
Re: dof calculator

http://www.altersky.com/photo/dof

New stuff #2: due to megapixel race the diffraction more and more becomes a meaningful thing even for big cameras :). so, i've added a resolution limit. here is the way it works:

- calculates 3 Airy disks: for red (625nm), green (500nm) and violet (400nm);
- shows the radius of the first minimum (that is, Reighley's criterion 1.22);
- in a basic mode doesn't permit to select an aperture faster than the one that makes Airy disk larger than the max circle of confusion;
- in a simple/useless modes just adds to the list of aperture values one for the diffraction limit, yet allows you to choose any value;
- in case of tresspassing the diffraction limit, colors the cells with airy disks with a border of a color of the tresspassing airy disk;
- and yes, it uses a conjugated focus instead of a lens' focal length (no idea why so many calculators use the latter). therefore, if the numbers differ from the calculator you are used to, first check for used wavelengths (most other calculators use midgreen ~546nm) and then try to compare using a very big focusing distance;

so, the usage, in a basic form you just can't choose a "wrong" aperture value.

in other modes if you choose a "wrong" value and your resolution is going to drop below your expected level (max circle of confusion), you will see a colored background in the diffraction cell.

ps. it's 5am and i didn't test it much, so, some bugs might be there :). i will test when i have time later.

p.p.s to be honest, i've not seen any other usable calculators allowing to see diffraction without scratching the head a lot. and yes, calculators that do the math "for prints" i believe are useless. i take pics for 16 years i guess, and in all that time i printed about a dozen of them, just to test a printer that i got from a friend.. :). tho, i understand that some people might have a different approach ;).

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