Quote Originally Posted by Franglais
I was trying to use vague marketing terms like "digital" meaning in this case "designed to be used only on a 'crop' APS-C sensor and not for use on a 'full-frame' 24x36mm sensor or on 35mm film".

People seem to think that there's a magnifying glass or something on the end of the lens that changes the view to adapt it to a digital sensor. There is no such thing - a magnifying glass would change the focal length.

I don't think anyone designs lenses for film any more. The manufacturers are gradually renewing their whole range of lenses (including primes) for digital. I can think of a few more changes they are making:

- avoid designs where the rear element is very small. If the light hits the sensor at an angle then it may not get into the individual photosites. This is a problem with 24x36mm sensors at the edges of the field. Many Leica rangerinder lenses have small rear elements. The M9 has specific sensor design with microlenses that are modified on the edge of the filed to look towards where the light is going to come from
- better lens coatings as you said. The sensor is shiny and reflects light back onto the rear lens element. If the rear element reflects the light back onto the sensor you get ghosting
- lower chromatic aberration. This is where a while line is split into a rainbow-coloured line. Each "pixel" on the sensor is actually four elements of different colours side-by-side, splitting the colours makes a mess of the fine detail in an image
- increase definition at the expense of contrast. You can always put the contrast back in postprocessing in the camera, but you can't invent detail that isn't there. Same with light falloff and distortion - if the designer knows that the lens is going to be used on a DSLR then he can leave some errors uncorrected (to improve other things) knowing that it can be fixed automatically in the camera without the user even knowing. (Don't ask me for examples - this is just something that the French press have been hinting at in the latest Nikon DSLR's)
:thumbsup: Yep

What I find amazing these days is the number of people that seem to believe that Digital re-invented the photographic wheel. All digital sensors did was make the ride better, the physics/science of photography stayed the same.

Just as the putting of an iron band on the first wooden wheels just made the wheel last longer. The wheel was and still is round. Still is after the addition of rubber, pneumatic tires, tubeless pneumatic tires etc. Of course the old wooden wheel, iron wheel and rubber wheel didn't need a tube or a valve stem. Those are just slight differences with the different road contact surfaces of the wheel.