On Wed, Mar 17, 2010 at 12:31 PM, Mark Roberts <[email protected]> wrote: > Larry Colen wrote: > >>The luminous landscape article on the 645D touched on something that >>I've been wondering about. Since it's always possible to throw away >>information digitally, but not recover it, why isn't anti-aliasing done >>in post processing if and when it's needed? > > Anti-alias filtering, *by definition*, has to be done before sampling > takes place (which in the case of digital imaging is at the sensor). > You can mitigate the effects resulting from aliasing after sampling, > but that's not the same as anti-aliasing. Pentax have decided that the > latter approach is, in fact, the one they're going to take. It ought > to be more practical with a 40-megapixel MF sensor than with > 35mm-class DSLR's. We'll have to wait and see. > > BTW: From what I've heard, cost is a major reason for eliminating the > anti-aliasing filter (it's reportedly why Kodak left it off their 14MP > full-frame DSLR). Apparently they're damned near as expensive as the > sensors they're used on.
One reason why you don't see AA on MF sensors is that you can do very good moire reduction in a RAW converter (CaptureOne in particular is excellent at this) while it's a lot more difficult to do on an ASIC without the sheer horsepower of a PC. Also if you have enough pixels, moire is less of an issue as it's related to the frequency of the detail matching the sensor's pixel pitch, that's increasingly unlikely with high-MP sensors. As a practical matter, the MF market doesn't use AA filters and the DSLR market does, Leica (and Kodak when they still made DSLR's) both are using technology from the MF market and thus use similar design choices to the MF cameras. -- M. Adam Maas http://www.mawz.ca Explorations of the City Around Us. -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
