If I were really serious about highest quality with a digital back for macro, tabletop photography I'd use a digitar lens optimized for parallelism of exit rays and at a maximum of about f/8, preferably less. I'd get the required DOF by using some of the newer focus stacking software and hardware.
Nate Potter, Austin TX.
When you do a 500 item catalog, it's not always possible to make every image from 100 captures.
At 5.6 the result would be the sharpest, but it would take a lot of time even with an electronic rail.
Indeed, you'd have to automate the distance scan using a stepper motor and sync each advance to a shutter actuation. 100 actuations could be done in less than 100 seconds per image. However, a 500 item catalogue would eat up 50,000 actuations on the DSLR. I suspect it takes longer to do the setups. Such DOF may be irrelevant for your purposes though.
Nate Potter, Austin TX.
None of the analog or digital lenses will be sharpest at 5.6, nor would they have their maximum coverage.Originally Posted by shlomibe
Assuming the camera is designed for digital so it can make the small movements digital requires and that the proper exposure is used the sharpest results will be at the diffraction limited f stops. F8 to 11 on most digital lenses and F22 on most analog 45 lenses.
Schneider say explicitly their best sharpness is at 5.6.
Ask them again.
Well, if you are not going to take the word of the Schneider engineers... why would you take the word of any of the members here? You are just going to have to conduct your own tests since you are not going to take the word of anyone here or at Schneider.
Specifically at f/22 all the lenses the OP mentions will show about the same degree of diffraction which will be around 30µm. Any slight variation due to a particular optical design will be insignificant IMHO. More variation in resolution between the candidates mentioned will be found at the larger apertures where the optical arrangements (formulas) leads to more variation in the degree correction of the image degradation parameters.
You don't need to do any lens testing to know the situation at f/22 insofar as diffraction is concerned.
Nate Potter, Austin TX.
Schneider engineers have their commercial agenda.
They've made a decision to optimize their digital lenses to f/5.6, and therefore have no interest to help me find the best lens for f/22.
IMO their decision is aimed at amateurs and pixel peepers, and they aim to create lenses which will show the best possible sharpness, which due to diffraction can be achieved at f/5.6. It is useful for professional photographers - not very much.
Regarding conducting my own tests - I would need 2-4 of the pertinent pretty expensive non refundable lenses at my disposal, which is not easy to get.
At this point, considering the feedback and materials I got, I've arrived at the conclusion, based on impressions not on concrete tests, that MFD lenses are the best solution for me.
Regarding "why would you take the word of any of the members here" - the reason is that forum members mostly don't have a commercial agenda.
Schneider's MTF charts show their digital lenses performing best at f8 or f11. I haven't seen any that were better at 5.6.
I think you'll see some differences at f22, but they may not be differences worth paying for. At least not as far as sharpness is concerned. The digital lenses are mostly diffraction limited at this point. The better macro analog lenses will be close behind. At wider apertures the analog lenses can't compete.
If you're looking for people with experience with these lenses on digital backs, try the getdpi.com forum.
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