ffmpeg – Best Lossless Video Codec for 8 bpc RGB image sequences?

I render 3D animations, many of which take days or even weeks to render at a time, and I need to keep a lossless archive of the output files. The output format from the render engine is 8 bit per channel (24 bit) PNG sequences, which are then modified heavily in After Effects to create a final composite.

I would like to find a way to compress these PNG sequences without losing any quality. Because there are many pixelwise operations happening in After Effects to the original source PNG files, it is imperative that I find a way to preserve the animations truly losslessly. Near lossless is not acceptable for this use case.

I have tested several codecs in ffmpeg, and so far, libx265 and libx264rgb seem to trade blows. Here is a table showing the filesize in GB I get when compressing losslessly using various codecs in ffmpeg (each column) for a variety of different animations I have made (each row):

I think both of these codecs have been around for a while, so I was wondering if anything else has come out recently that could get the file sizes down a lot more? Or are libx265 and libx264rgb the pinnacle of true lossless compression?

In case it is relevant, these were the commands I used to compress for each codec:

cmd = f'ffmpeg -ss 0 -i "{unc}" -t {tt} -y -c:v huffyuv -lossless 1 "huffyuv_lossless/{name}"'

  cmd = f'ffmpeg -ss 0 -i "{unc}" -t {tt} -y -c:v ffvhuff -context 1 "ffvhuff_lossless/{name}"'

  cmd = f'ffmpeg -ss 0 -i "{unc}" -t {tt} -y -c:v utvideo "utvideo_lossless/{name}"'

  cmd = f'ffmpeg -ss 0 -i "{unc}" -t {tt} -y -c:v ffv1 -preset slow -qp 0 "ffv1_lossless/{name}"'

  cmd = f'ffmpeg -ss 0 -i "{unc}" -t {tt} -y -c:v libx265 -x265-params lossless=1 "libx265_lossless/{name}"'

  cmd = f'ffmpeg -ss 0 -i "{unc}" -t {tt} -y -c:v libx264rgb -preset slow -crf 0 "libx264rgb_lossless/{name}"