Lens are designed by a process called ray tracing. What that means is simply drawing lines simulating light rays through a set of lenses. Change the lens design slightly and do it again. They go through this process many many times until as many aberations as possible have been eliminated. As you can imagine before computers that was a long drawn out laborous project. Usually it ended at a point that was considered "good enough". Some of those lenses had that indefinable quality.
Now with computers it is fairly easy. So they keep going until the lens design is fully optimised. However, lens design is a trade off, do you want maximum sharpness, maximum contrast, maximum smoothness? Do you want it to work best close up, or at infinity? Or do you want to design for a compromise of all of these. With your nifty supercomputer you can do anything you want, but some of these things are mutually exclusive. You can not have it all.
So tell me if you can design your lens for the best looking photograph, or the best magazine test results but not both; and your job depends on you employer making money with your choice; which do you choose? Pentax being different chose photo quality in the past. Since I have never used their newer lenses I do not really know if they still do.
mike.wilson wrote:
Wonder if it has anything to do with coating. This was very hit & miss for the first 100(?) years of photography.
-- graywolf http://graywolfphoto.com
"You might as well accept people as they are, you are not going to be able to change them anyway."
