[Papou]

G'day gang..Some time back someone posted athread regarding fee software programs for PC and Pocket PC's and one of those programs was a depth of field calculator.
Finally got it downloaded and running both on Pc and pocket PC but have a wee problemo trying to work out what they term as resolution..
Eg
First cab of the rank is you tell it the focal length of the lens
Teleconverter if used
Then F Stop
Resolution(in Lines/mm-lines cm- orlines /inch)???..
This is the wee area i have a problem with?? the lines per!!?? as always resolution to me was Pixels etc..
Anyone shed a wee bit of light here for me please??..
Cheers

[PDL]

I may be the one who lead you down the path of DOF calculator for the Pocket PC. So here are two places to go in an attempt to understand what Lines Per Millimeter really means.

First my old friend Wikipedia - Image resolution - Wikipedia, the free encyclopedia
Not all that helpful - but at least you can get a understanding of what is meant by LPm. (Down at the bottom - they state that 35mm motion picture film can resolve 6,000 lines per mm - I don't think digital is there yet)

The second one is a article from Luminous Landscape - talking about DOF and therefore LPm.
DOF
I quote:
"Now, the camera industry figures for the purposes of calculating depth of field (and therefore Circle of Confusion) that an image is typically enlarged 5X from the negative to a print. This would mean roughly a 5X7" print from 35mm. So since 0.1667/5 = 0.0333, this is the Circle of Confusion that many 35mm lens manufacturers use when establishing their depth of field tables and lens markings. Canon, for example, confirms in their book EF Lens Work II, that they use 0.035mm as their COF for all modern EF model lenses.

By the way, .0333 translates to 30 lines/mm ( 1 / .0333 = 30). And, 30 lines per millimeter is the theoretical maximum resolution needed on a print, as described in my earlier article Understanding Sharpness. It all hangs together."
The bold is my my emphasis.

So - it seems that lens manufactures just might be using 30 LPm as a basis for their design. That is a good jump off point. DoF Master Hyperfocal Distance and Depth of Field Calculator - DOFMaster allows you to calculate your own COF and also gives a COF of .030 for 35mm (135 format).

As always, you will have to judge for yourself and make the tool fit your desires. (By the way, the article at LL is very good - especially the lower half)

Hope this helps a little.

The Elitist - formerly known as PDL

[Papou]

Greatly apprerciated.Now?? does that mean using a 50mm f1.4 lens or whatever for my K10D ide set that value to 30??..Or does it work itself out depending on lens used??...
Cheers