Originally posted by y0chang Digital sensors have micro lenses that gather light at oblique angles. Film lenses are not optimized for these micro lenses means that there is a loss of resolution and vignetting.
Leica has struggled with this issue since the light angles of their rangefinder lenses hit the sensor at crazy angles due to the short registration distance.
LEICA Barnack Berek Blog: THE FUTURE OF SENSOR TECHNOLOGY AT LEICA
Also it was mentioned that the FA limiteds were designed and tweaked by painstakingly examining images that were made on film. This is contrast to the usual computer-assisted optical design method. That means they were never tested for Digital.
I was thinking the same thing. That doesn't mean that they aren't still better on digital if you are making prints, but most of my images are viewed on a 55" 4k TV. So neither my input device nor my output device was used in the design criteria.
So I wonder if the criteria still hold up. I've never seen any quantifiable data suggesting film and digital sensors have to be different. This is as far as I know an un-researched area of knowledge, at least in terms of publicly available documents. I wonder if anyone will ever again use this design process, or if remnants of this process still linger at Pentax.
The common practice of releasingf specs based on analysis of the design by a computers certainly would suggest not. It would suggest they aren't even doing testing on the actual product, but using numbers of un-known reliability. After all, most of us don't care what the theoretical possibilities are, we are more concerned with the performance of the finished product.
That being said, those of us who use film area lenses have to be sensitive to conditions that might cause purple fringing, which apparently was not an issue on film.
All of my film era lenses purple fringe more than my more modern designs.