using a telephoto lens as a tube len for infinity corrected microscope lenses - impact on image quality?

[pu5z3k]

Hi,
as in the topic, I wonder what quallity impact has using a telephoto lens as a tube-lens on the final image quality.

Is it worth paying more for a better quality lens for this? does its light matter (f2.8, f5.6)?

I am currently thinking about buying the Lumix 100-300 and there are two versions (the older one is optically worse) - but much cheaper.

Currently, I use a 40-150 2.8 Pro lens, the quality of which is captivating in a set with the Mitutoyo 5x, but even at 150mm there is still a slight vigneting effect.
On the mitutoyo 10x, this effect is even more vissible, in addition, you can see a decrease in image quality in the middle of the photo from the center

It's hard for me to find a good article on this topic - that's why I am asking you for help.

[Lou Jost]

There are several tube lens tests here and on Robert O'Toole's website closeuphotography.com/

You don't need to limit yourself to MFT lenses. In fact, I think larger-format lenses are more uniform in quality across the image.

[JKT]

In general higher f-number is more likely to cause vignetting, BUT there are many other factors in play as well. The first thing to remember is that the diagnostic value is actually the aperture diameter. So in that sense 200mm f/5.6 is equal to 100mm f/2.8. Another thing to remember is that the lens design has a huge impact on vignetting. I would not expect 180mm f/3.8 to vignette, but it does ... seriously. I suspect the input pupil is too far back inside the lens ... or something. Testing is usually in order.

[Lou Jost]

Zooms tend to vignette more than primes of the same focal length, and tend to vignette greatly when zoomed to shorter focal lengths. For example, most FF 135mm prime lenses don't vignette much ( if at all) on MFT sensors when used with a Mitutoyo objective, but an 80-200mm FF zoom lens can start vignetting at 150mm.