Hi Sam!
I need a bit of clarification here:
1) doing a local low res test render they look great
2) when I try to render over deadline or through DR at high res, they come out much darker
3) I've tried doing a quick render at high res (6k vs 2k) and after 3 passes the caustics once again look great
Do I understand right that the issue with dark caustics only appears when rendering in high res over Deadline or DR?
What exactly do you mean by high res?
Generally, there is a known issue with caustics rendering darker as the resolution goes up. This can be worked around by increasing the "initial lookup radius" in the caustics solver's devel settings.
I would recommend doubling the value first, and checking how it works. If they are not bright enough, you can try doubling it again, and so on.
I am not sure if increasing the photon count is a good idea, but if it doesn't result in super high RAM usage and too slow rendering, you can keep the boosted number.
Also, caustics don't currently work correctly with render regions. If you are rendering a region, it just won't work. The only way to make sure they render fine is running a full production render.
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