"What I dont seem to understand is why the new digital lenses arent optimised at the smaller apertures, say f22? Generally I would think most users of larger format lenses would want max depth of field with sharpness.
Hello IvanDiffraction Limited
is the key issue here. Reading this web page is helpful...http://www.cambridgeincolour.com/tutorials...photography.htm
Past F11 on my 33mp, 6x4.5 sensor with my digitars I am diffratction limited. I gain corner sharpness and have less lens falloff when stopping down more, but the picture is softer in the center.
With my 35mm digitar I always shoot at F11. This lens is equivilent to a 90mm lens on my 4x5. I would guess that with the 35 digitar set at F11 the depth of field is similar to the 90mm lens set at 22 or 32 on a 4x5 camera. So I have gained 2-3 stops of light with the same depth of field by going to the smaller format.
The lenses are not optimised for F11 versus F22 for the reasons you are thinking. By using the calculator on the cambridge site you will see that you can stop down more and still get a sharp image by using: A larger format, lower resolution film or sensor, or printing smaller.
As you make the sensor smaller, higher resolution, or make larger prints, your lenses will become diffraction limited sooner as you stop down (but the shorter lenses on the smaller formats need to be stopped down less).
It is not about lens design or optimization, but about laws of physics, so to speak.
I hope this is in English... this is a tough topic to write about clearly.