Correcting for linear "vignetting" from Shutter

Hey everyone,

I’ve recently gotten a Viltrox 56mm f1.7. It works great, however it does have a design flaw which seems to affect some fast third party lenses on alpha 6000 cameras, where electronic first curtain shutter leads to slight shadowing from the shutter at speeds higher than around 1/2000. This has been previously described in other forums, e.g. A very strange behaviour with the Viltrox 56mm F1.7 E.

Here’s an example of the issue at it’s worst, 1/4000 on a bright sky:

Fortunately I rarely have any need for shutter speeds that fast and can easily disable EFCS if I do. However, I have ended up with a handful of otherwise nice images affected by this that I’d like to rescue. I’ve found some success using the vignetting module in darktable with a square shape to brighten these areas, but it’s very fiddly and never quite perfect.

Ideally, I’d want to characterize this “vignetting” once and then apply it to other images, like is done with the lens correction module. But it seems like lens correction only supports circular vignetting and can’t do corrections depending on shutter speed.

Do you have any ideas, or are there any existing solutions for this problem?

A very minor problem in my view. The correct solution to this problem in my way of thinking is to apply a second instance of exposure and use a gradient drawn mask to equal out the exposure across the frame. This is not a vignette problem in my view but rather an uneven exposure across the frame. Should be really easy to fix. If you supply a RAW file we could test my suggestion or any other suggestions people may have.

Thanks, I’ll give it another shot that way! I’ve attached the raws for the demo image as well as a defocused picture of a white lampshade at the same settings

DSC03286.ARW (23.6 MB)
20241225_0008.ARW (24 MB)

Here is a quick go at the chimney. The lamp is possibly showing horizontal vignetting as well as corner drop off vignetting. That one would be more painful to fix.


20241225_0008.ARW.xmp (11.4 KB)

4.30 in the morning I should go to bed now.