On 21 Jul 2005 at 16:34, Shel Belinkoff wrote: > I don't know what demosaicing is, but here's what I do know: The pic made > with the istD and the 18mm lens was shot using the highest quality JPEG set at > whatever the normal settings are for contrast, sharpness, and saturation, and > received no further processing afterwards other than to be resized. The > aperture chosen was the same for both lenses, 4.0 or 5.6 iirc.. The pic made > with the 28mm lens was scanned straight and resized in PS. There was no > sharpening or other adjustments used on the images except that a curves > adjustment was used to bring the tonality of the images closer to one > another.
Several variables are in play here that could alter the perceived DOF in the images that you presented. Firstly the in-camera JPG is subjected to fairly harsh sharpening at the default settings, far more harsh than I am when I post process my RAW images. Secondly depending on the scanner its resolution may or may not be able to resolve all the detail held in the film image. Lastly when all is said and done regardless of the number and accuracy of calculations made perceived DOF is just that, it's more complex than simply applying a calculation. DOF in a print is relative to absolute lens sharpness (a soft lens will appear to have a greater DOF than a very sharp lens as the edges and demarcation will be less pronounced) and print/image size and in the case of digital images may also be affected by the algorithm that is employed to resize it. I appreciate the fact that you took the time to produce the test shots and it really brought home the point that was being made regarding equivalent AOV and perspective but I believe that you would really have to design a very specific test to validly compare DOF between these two systems. Cheers, Rob Studdert HURSTVILLE AUSTRALIA Tel +61-2-9554-4110 UTC(GMT) +10 Hours [EMAIL PROTECTED] http://members.ozemail.com.au/~distudio/publications/ Pentax user since 1986, PDMLer since 1998
