One-sided (asymmetrical) light falloff issue (Samyang 85mm 1.4)

Hey all,

I recently bought myself a Samyang 85 1.4 and I love it.
However, I seem to have a problem with light falloff.

I know that this lens has some apparent vignetting at wider apertures, but this looks a bit different and more extreme than usual.
The vignetting that I get in pictures (which does not disappear until f/5.6) is asymmetrical; it seems to be present only in one side of the picture. I will show you some pictures to illustrate the problem.

I'm going to guess that you have a blade problem. Send it in or return it.

KirkS518 wrote in post #16960593
I'm going to guess that you have a blade problem. Send it in or return it.

That's what I was thinking aswell, yes. However, this problem is also present when shooting wide open @ 1.4. I will post some more examples.

Here is a clear example:

For these pictures I shot at different apertures. Those on top are taken with the camera's right side facing downward and those on the bottom are taken with the camera's right side facing upward.

As you can see, one part of the image is clearly underexposed and the other part is overexposed. Using a narrower aperture like 5.6 results in the entire picture being underexposed.
Conclusion = there is a lot of light fallof on every aperture.

I assume that the problem does not happen with your other lenses. Otherwise it could be a shutter problem with your camera. The shutter blades move vertically across the short side of the sensor. If one of the blades is slowing down or speeding up, it would cause one side of the frame to be exposed differently.

But my explanation cannot account for the entire picture being underexposed at f/5.6. Please tell us what metering mode you used for your test shots.

I'd say it's an aperture issue. I had an issue with my first copy of the Samyang 85mm in which it wouldn't stop down for a few seconds after I adjusted the aperture dial, sometimes it wouldn't adjust at all, other times it would work fine, so it wouldn't' surprise me if someone else had a funky aperture issue.

That said, I'm super happy I got a second copy, it's a fantastic work horse of a lens

RodneyCyr wrote in post #16962142
I assume that the problem does not happen with your other lenses. Otherwise it could be a shutter problem with your camera. The shutter blades move vertically across the short side of the sensor. If one of the blades is slowing down or speeding up, it would cause one side of the frame to be exposed differently.

But my explanation cannot account for the entire picture being underexposed at f/5.6. Please tell us what metering mode you used for your test shots.

My other lenses are fine. It's weird because I can't really see anything within the Samyang lens that looks off.

For the shots I used evaluative metering.

I have already contacted the shop I bought it from and they are willing to send me a new copy, which is great.

So I returned the lens and got a replacement. This one is free of all issues!

I would say the lens elements are off center. Happens with all makes of lenses.

People pay alot of money for a GND filter.. Glad you got it squared away!

I would like to add that this problem was only present when using fast shutter speeds like 1/1000 and above...

What would be the explanation for that?