Asymmetrical vignetting on EOS R at wide aperture with Laowa lens

[Massafornian]

Camera: EOS-R
Lens: Venus Laowa Argus 45mm f/0.95 (manual lens)

Problem: When my lens is opened wide to f/0.95, there is vignetting that is asymmetrical—there's a gradient fade on one side of the photo. I might attribute this problem to the lens, however when looking through the live image in the viewfinder, the vignetting is symmetrical, as I would expect. Only the resulting photo has asymmetrical vignetting—this suggests that the problem is with the EOS-R. I always thought that the viewfinder is WYSIWYG, so this difference between preview and final photo is odd.

I expected vignetting with a lens this fast, but for it to be symmetrical.

I've tried other lenses and cannot reproduce the problem.

Is there a camera setting producing this issue? I've attached three photos. You can see the gradient vignette on the right side of all three photos. There's hardly any vignetting anywhere else.

Thanks,

Massafornian

[Waddizzle]

Vignetting is caused by lenses.  The issue is being caused by your Laowa lens.  This would explain why you only experience this issue with this one lens.  

If camera settings were the issue, then changing lenses should not make the issue go away. 

[Massafornian]

But why then is the viewfinder preview not showing the same thing as the resulting photoe?

[ebiggs1]

"Vignetting is caused by lenses."

The VF is an electronic device and not exactly what the sensor is seeing.

[ebiggs1]

I had never even seen a Venus Laowa Argus 45mm f/0.95 so I had to look it up. Even though it is several hundred bucks it is a cheap lens. It is going to suffer from all the lens issues top manufacturers like Canon and Sigma or Tamron try to eliminate. I would guess if Canon made such a lens it would be several, many, thousands of dollars. 

Just use it and enjoy it for what it is. I don't know if PS has a lens correction profile but if it doesn't you can make one for it. Choose Filter > Lens Correction>Custom. Or click 'Search Online' to look for additional profiles created by the other Photoshop folks.

[Massafornian]

Thanks for your feedback.

I've decided to sent the lens back.

-Massafornia

[SteveN_SHIJ]

I feel sorry that I didn't see this question earlier. I believe it is a good lens. I own a 33 0.95 argus on my eos r7 mirrorless body.

[ebiggs1 · Accepted solution]

Frankly I would too. Sorry it didn't work out but you know the old saying if it looks too good to be true it probably is.

Even a f1.2L is extremely difficult to make. Drop to F1 and it doubles the problems. Drop to f.95 and well you know exponentially more problems.

[SteveN_SHIJ]

Oh my gosh, I can't believe no one pointed out such a simple issue. This is not a problem with the laowa lens, nor can it be said to be a problem with the Canon camera body. The problem with uneven exposure is that you are using the default shutter setting, electronic 1-st curtain shutter. This is an inherent problem with electronic front-curtain shutters. Because the electronic front curtain and the mechanical rear curtain are not on the same plane, which leads to uneven explosure and cutting off the bottom of the bokeh at high shutter speed and/or fast apeture. The solution is to switch to a fully mechanical shutter or electronic shutter. It makes sense that the electronic first curtain shutter is the default setting, because it is not like an electronic shutter that will cause the cmos ADC to switch from 14bit readout to 12bit, resulting in a reduction in dynamic range, nor will it produce shutter shock like a fully mechanical shutter does. It also actually extends shutter life because the mechanical front curtain has twice as much movement as the electronic front curtain shutter curtain.

[SteveN_SHIJ]

The same goes for the fact that you can't see exposure unevenness in live view. Live view is CMOS outputting pictures to LCD/EVF at low resolution and high frame rate in an energy-saving mode. Actually it is using a fully electronic shutter.