Originally posted by bdery You have looked at primes, and considered mostly older lenses. These, in general, offer sharpness that is less uniform across the frame. Center might be superb, while corners might be soft. Newer lenses are designed (again, in general), with sharpness across the frame as more important. In particular, field curvature is taken into account better than in "the old days".
Sorry I have to contradict to this statement. I think there is no such general rule to the uniformity of the sharpness about the whole frame. For every new lens designed the various characteristics of a lens are set by its developer newly. And if a developer pronounces center sharpness in a new lens you will not have uniform sharpness.
This is absolutely true for my DA 18-135 which has absolute no sharpness at the borders at 135 mm. The priorities where somewhere else obviously.
One may argue that pimes are better in this way, until having a look at the Sigma AF 30 mm / 1.4 which behaves like the worst portrait lens ever in this respect. And that is a full frame lens, not one designed for APC as a standard lens with portrait in mind. This lens is clearly beaten in uniformity across the frame by the much older Tokina RMC 17 / 3.5 which is on par with the SMC DA 15 / 4.0 on the borders and corners at 5.6 but falls behind the DA 15 in the center of the image where this outperforms the Tokina and it's own borders clearly. No uniformity again. But of course better performance over the older lens in all.
All tests cited can be found here:
Pentax K Lens Tests
This aside, what I am really interested in is, will the stiching solution work? Has anyone done it already? Don't you have problems with the sharpness at the seams?
Using a 50 mm macro would be the obvious solution then, wouldn't it?