One of the things currently missing from Reshade is a good vignette shader. The one we currently have has no highlight priority which results in dimmed highlights.
Here is a comparison:
Vignette from Reshade (notice dimmed highlight in the sun): grab.by/Jxcq
Vignette using Lightroom 6: grab.by/Jxcu
I would also consider simpler controls that are easier to understand for a new vignette shader. Lightroom's vignette controls are very easy to understand and give great results (grab.by/Jxcw) It's also easier to achieve more square vignettes for widescreen monitors than it is in Reshade.
Last but not least, the ability to move this shader to the front of the pipeline and to the back is pretty important. This way users can decide if the want lens vignetting or post vignetting. There is a difference.
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