On 27 Jun 2004 at 16:09, Shel Belinkoff wrote: > Here's a question since not everyone has PS CS or other programs: Why can't > these lenses be made so there's no or minimal CA? Seems to me that all the digi > folks have gotta put up with this crap, and the solution offered is to go buy a > $600.00 program to remove it in the editing process. Regular lenses pretty well > dispensed with that years ago. Feh!
Mast all wide angle lenses exhibit some CA, the problem with digicams is a little more complex, sensors have two characteristics that are very different from film. Firstly for all intents you can consider film to have no depth, light that strikes it at an acute angle will be recorded pretty accurately, with sensors that have micro-lenses which are position above the actual light sensitive substrate. So this means that acute light angles are going to cause all sorts of problems such as vignetting and spill to adjacent sensor sites. Secondly unlike film the majority of sensors measure the primary colours in slightly different positions, these measurements are then used to approximate the colour that would likely have been at the actual pixel site. As you can imagine this approach can be easily derailed and the colour separation caused by CA is something it doesn't handle well, in fact most demosaicing algorithms tend to magnify the effect in the final image. These are just some of the limitations we have to deal with using the current technology, digital image capture is no panacea but it does have a lot of positive aspects too of course :-) 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
