Aperture afecting barrel distortion (EF 50 1.8 + Canon adapter/Viltrox)

Started 2 months ago | Discussions
cancolour New Member • Posts: 9
Aperture afecting barrel distortion (EF 50 1.8 + Canon adapter/Viltrox)

Someone tell me what I'm doing wrong here, this is really strange.

I was looking through some test shots of the EF to EF-M adapter + 50MM 1.8 STM combo and comparing them to the Viltrox + 50MM 1.8 STM, when I noticed that the barrel distortion appears to decrease with stopping down on the Viltrox. I checked this against the Canon adapter and the effect is there as well, it's just harder to observe because the distortion is more pronounced on the Viltrox.

It's hard to see this in browser, but it's obvious in the bottom center around the 10 mark when rifling through the images. All shots were taken on a tripod; lens corrections are turned off in camera and in software.

Could this be attributed to differences in focus and the depth of field? (I did refocus for each shot) Interestingly, I couldn't observe this effect with my EF Tamron 1.8 SP, where barrel distortion appears to be constant with both adapters, but that lens is sharper overall so maybe that's part of the explanation.

Canon Adapter + EF 50 1.8 STM

Viltrox + EF 50 1.8 STM

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