Originally posted by macTak The K and M 50/4 Macro and the A50/2.8 macro all have curved rear elements and so shouldn't have this issue (I too experianced it with the Tamron). Intersting that the FA50/2.8 has this issue; it's element isn't flat, though it is not far from it.
Thanks a lot guys
With the FA-50mm I only have the problem at the three stops f. 25-29-32. But sometimes I need to use these stops, since a tremendous ammount of light is necassary/desirable.
I normally use focus stacking for jewelry and such. But I have to use more shots at F11 than F32 :-) More shots represents a problem with 50mm, since the sort of wide angle image will get distorted too much when movig the lens forward (w. a focus rail). So if I take too many shots for stacking, Photoshop will have problems blending the layers properly. It's much easier with a 100mm :-) But sometimes - for larger objects - the 100mm gets too close. So - sharpness is not an issue, as I use stacking - my images are very sharp. I just wish I didn't get the blue spot.
Full frame is not really an issue yet, since the new FF Pentax haven't arrived yet..
I may try to use the 645D for which I have a tremendously good 120mm macro lens :-)
Regards
Jens