Issue with renders losing colour-depth? Maybe?


#1

Hey everyone,

I’m trying to figure out an issue I’m having. I’ve got an animation rendering out. This is using Corona but I’m thinking the issues is related to C4D, but I also am just speculating and don’t know what’s going on.

Basically, the animation is rendering out and you can see each individual frame completing in the picture viewer. The frame completes, the status dot goes green to indicate that it’s done and stored in RAM. Now, the issue seems to happen when the RAM gets full and the render status dots go grey, indicating that they’ve left RAM and are now temp files stored on the hard drive.

As soon as that transition happens, the frames file size drops significantly (1MB down to 340kb) and it looks like the image goes 8-bit as MASSIVE banding happens. You can see it in the shadows on the floor, under the vanity, etc.

If I sit at the machine and save each completed frame as it goes green, but before it goes grey, the image saves out fine.

Any help resolving this would be appreciated. I’m really hoping for a fix as support hasn’t been able to do much other than point blame back and forth with no real solution.

Example:


#2

What file type are you saving the frames as? Are you using a format that can store the colour depth you want?

A drop of file size of that magnitude would suggest you are saving frames as JPEGs, which you should definitely avoid…


#3

Currently saving them out as EXR to maintain Corona post-edits but, as long as I save them before they leave RAM and get saved as a temp file by C4D, they’re fine. If I leave the animation rendering, once the RAM is full (around 140 frames in) the frames that it then transfers to the hard drive go from looking great, to that 8-bit colour banding.

Not sure if that makes sense… basically, they render as they should and, as long as I save them before the green status dot goes grey, they’re fine. If I don’t catch them before they leave RAM, they take a major hit to quality.


#4

This doesn’t make sense: C4D doesn’t wait to save your frames, it saves them as soon as the frame is finished rendering (using the settings you close in the Render Options > Save dialog).

C4D doesn’t save temp files per se, and the free RAM state of the Picture viewer does not determine when things get saved.

Corona may have some funky save behaviour I am unaware of, however, but I don’t think that it could cause this issue. Especially with the drop in file size, which is very, very small for an EXR. Are you sure you are not somehow saving as JPEG or something else?


#5

I’m sure they’re not being save out as jpgs and I’ve checked for any compression settings. I’m really confused. As the frames complete in the C4D picture viewer, they all appear normal and with the green status dot. I can save them out individually from there with zero issues. If I let this render out over night and I don’t save the individual frames before the dot turns grey (which I believe means no longer cached in RAM), then they start to get that file size loss and banding.

Normally I’d let the entire animation render out and then save the frames and it’s fine. I’m not sure what it causing this… and it’s confusing me so much since they save out fine if I get to them before the dot changes to grey.


#6

This is not normal C4D behaviour, so I would check with the Corona devs if you haven’t already…

Other possibilities: Render to a different format (.HDR, PSD), or even a 16-bit mov.


#7

Thanks for your help. I’ve reached out to them and Maxon in hopes that someone can figure this out. Haven’t encountered something like this before :confused:


#8

How do you normally save the images? Can you post a screenshot of the C4D render dialogue? If there’s some sort of Corona post pass happening, AFAIK it should be applied after your renders have been saved to disk (i.e. in their final .exr format).


#9

Corona renderer forum is meant for this kind of question. Perhaps try here https://forum.corona-renderer.com/index.php?PHPSESSID=7l1a3h0elgg1ainu6rh0rr835e&board=23.0