Sony 90mm quality degradation when stopped down?

[hedonist222]

I recall quality from the Canon 100 f/2.8L began degrading at f/24.

 

I have not yet tested the Sony 90mm yet.

 

Has anyone established this yet? 

[Architeuthis]

Hi Hedonist,

 

The loss of resolution, due to diffraction, is pretty similar between these two lenses (stopped down the resolution of different sensors is by far not limiting):

 

https://www.lenstip.com/214.4-Lens_review-Canon_EF_100_mm_f_2.8_L_Macro_IS_USM_Image_resolution.html

https://www.lenstip.com/561.4-Lens_review-Sony_FE_90_mm_f_2.8_Macro_G_OSS_Image_resolution.html

 

The smallest aperture possible with Sony 90mm is f/22 (probably because of the problem of loss in resolution).

It is, of course, a matter of personal taste, and much more of the required DOF, how much one stops down such a lens, but (theoretically) best results are obtained at f/4...

 

Wolfgang

Edited September 22 by Architeuthis

[Chris Ross]

All macro lenses lose resolution as they stop down due to diffraction. Here is the MTF testing on lensTips:

 

https://www.lenstip.com/214.4-Lens_review-Canon_EF_100_mm_f_2.8_L_Macro_IS_USM_Image_resolution.html

 

and the 90mm macro:

 

https://www.lenstip.com/561.4-Lens_review-Sony_FE_90_mm_f_2.8_Macro_G_OSS_Image_resolution.html

 

The numbers are not directly comparable as they are tested on different sensor resolutions but you can see a drastic drop in quality at f16-22, so I expect you will see degradation at similar apertures on both lenses.  The plots basically measure resolution and you can see it reduces after f11 or so.  Optical limits also has a plot which is a little more complete for the 100mm f2.8 only, the dramatic drop beyond f16 is more obvious:

 

https://opticallimits.com/canon/canon-rf-100mm-f-2-8-l-usm-is-macro/

 

 

[hedonist222]

7 minutes ago, Architeuthis said:

Hi Hedonist,

 

The loss of resolution, due to diffraction, is pretty similar between these two lenses (stopped down the resolution of different sensors is by far not limiting):

 

https://www.lenstip.com/214.4-Lens_review-Canon_EF_100_mm_f_2.8_L_Macro_IS_USM_Image_resolution.html

https://www.lenstip.com/561.4-Lens_review-Sony_FE_90_mm_f_2.8_Macro_G_OSS_Image_resolution.html

 

The smallest aperture possible with Sony 90mm is f/22 (probably because of the problem of loss in resolution).

It is, of course, a matter of personal taste, and much more of the required DOF, how much one stops down such a lens...

 

Wolfgang

 

Thank you for this helpful input, Wolfgang. 

 

You are most correct in that, aside from degradation, there are other more commanding variables.  Such as DoF as above. 

 

I actually did test the lens from f22 to f16 but I am opting not to rely on it (test results) because my subject was not stationary. It was fast moving a nudibranchi and therefore my area of focus shifted between shots. 

I will repeat this with a polyp or similar soon. 

Edited September 22 by hedonist222