Using a speedbooster and its impact on image quality.

[3dpan]

My experience involves using a Viltrox Speedbooster for astrophotography.

A star field is a very severe test of a lens "IQ".

I found that the Viltrox introduced tangential astigmatism to lenses 135mm and shorter.
Specifically
(i) Samyang 135/2
(ii) Olympus 100/2
(iii) Samyang XP 35/1.4

Longer lenses eg Nikon 180/2.8 D and Zeiss Mirotar 500/8 did not show any tangential astihmatism.

I think this proves that the astigmatism is in the shorter lenses and not in the adapter. Which is also what would be expected - have you tried those lenses with an adpeter without optics in it?

I raised the question with Metabones, does their Speedbooster exhibit the same affect ? and sent them example images.

No reply after two years so I assume they don't know/don't care.

I have just checked my files, using the OM 100/2.0 on a star field. (and Olympus E-M5 II)

Lens with plain adapter, no sign of tangential astigmatism (TA). Example below, uncropped.


OM 100/2.0 @f2.8 -- plain adapter



But, same lens with Viltrox SpeedBooster, obvious TA. Example below, uncropped.


OM 100/2.0 @ f4 + Viltrox 0.7X Speedbooster

 

[Mark9473]

Thanks. Nice images.

I have some old bookmarks comparing the Viltrox and the Metabones. I 'll see if I can find them.