jjlphoto wrote:
1- Regarding CA, film lenses had light rays falling on a surface that had physical depth due to the colored layers, hence the coatings and diffractions were optimized for the rays to penetrate those depths differently. With a sensor totally flat, digital lenses are optimized to bring all RGB rays onto one surface.
I find it hard to beleive that they can design and can control the lens performance to the extent that each 3 colors focus to a different distance that are mere microns apart. And what about colors other than red, green or blue? It seems that for most lenses they were lucky if they could get all the colors to focus on the same plane, much less control it so each color focuses precisely in a different plane.
jjlphoto wrote:
2- Regarding precision- film lenses were somewhat compromised to allow for depth of focus that corresponded to the somewhat convoluted nature of film itself, and the sagging and buckling it would normally have. Digital lenses have a shallower depth of focus (and hence better resolving characteristics) because the sensor is now perfectly flat.
Further to point number 1, these differences swamp the differences in the optimum focus point between the layers. I also don't understand how they can change the "depth of focus". There is no "depth" to the focus plane. If there is a compromise, what is the nature of that compromise and how is it achieved?