Originally posted by newarts I don't follow this. Why would the zeiss perform worse with no intervening lens than with an intervening lens (the 300:50 arrangement)? How could the resolution of the 50mm Zeiss be improved by even a perfect 300mm lens?
The Zeiss focusses at infinity. This is its sweet spot. Macro lenses are designed for short subject distances, normal primes aren't.
A reverse mounted 50 is forced to operate close at its near focus distance. At 6:1, the bellows would have to be 7f or 350mm which is still less than the 460mm near distance limit of a (Zeiss) 50.
Not only the lens woudn't be used at a non optimal setting, it would be used outside of its specification. And this where we require it to outresolve a sensor by 6x! I wouldn't expect usable results.
(When pixel peeping but this is what counts as otherwise, I can use the DA35 and crop. The DA35 is an exceptional lens and cropping a DA35 may beat a bellows approach -- what most people forget: a 5:1 macro resized for the web (900px) only is a 1:1 macro...
So, to the OP ... Wanting a 5:1 macro for a 24" screen (1920px wide) means wanting a (
tac-sharp) 2:1 macro really)