Image quality 90 macro vs. 60 macro

Started Feb 16, 2023 | Discussions thread
Jonas Palm Senior Member • Posts: 1,206
Re: Good service to the community

JasonTheBirder wrote:

Thanks! I think this kind of test is very useful. Direct shots of paper and details can tell you a lot about the differences between two lenses. At high magnifications, lenses can show distinct optical problems not visible at low magnifications.

As a case in point, I've found the Venus Laowa 50mm f/2.8X macro to be excellent at f/2.8 to f/5.6 past 1:1 magnfication. But at f/8 and beyond, the lens falls apart, whereas that is not the case at normal distances like landscape.

I know part of the trouble at high magnification is diffraction but I wonder if some lenses do much better than others comparitively (like % decrease is minimized) and if so, why is that the case? Or is it just a matter of the lens being overall better at high magnifications?

Diffraction is independent of other lens flaws. Contrast differences at f8 in m43 is in this case probably down to differences in exact focus (extremely critical at close range, it really is a plane of focus) or how well corrected the lens is at different focussing distances. The Olympus 60mm f2.8 doesn’t get enough credit for its three different focussing groups! It is also an aspect where I suspect the 90mm f3.5 can be doing a really good job. It’s difficult to test and assess stringently, and so doesn’t get all that much attention. 
With all due respect to Martins testing, I would be hesitant to draw many conclusions from single lens sample, single shot comparisons. There are just too many things that can be slightly off for general conclusions to be drawn.

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