"I have not failed 700 times. I have succeeded in proving that those 700 ways will not work. When I have eliminated the ways that will not work, I will find the way that will work."
---THOMAS EDISON on inventing the light bulb.
The QuickTime Animation codec can be lossless. The Lossless preset that ships with AE, for example, is lossless provided that you don't wish to keep any more color information than 8 bits per channel. It does not introduce any compression artifacts at all.
As far as I know all ProRes variants are lossy to varying degrees. That said they can hold more than 8 bits per channel of color information as well.
As you've seen from the responses already, it's not as simply a question as it seems :)
[greg howell]"Is the animation quicktime codec (native to AE) truly loseless? If i render again, and again, and again will i lose any information?"
If your project is set to 8bpc, then yes, Animation is lossless. You can render again and again with no visual or mathematical loss.
[greg howell]"If not, which codec is truly loseless?, ProRes 4:4:4:4?"
ProRes 4444 is not mathematically lossless. It is very high-quality, and as John and Darby have suggested, it supports deeper color.
If your project is set to 16bpc, you may be better off using ProRes 4444 as an intermediate than Animation. The ProRes 4444 is mathematically lossy, but it will take a few generations before that loss becomes noticeable. The additional color depth ProRes 4444 preserves (up to 12 bits) would make it a better choice here than Animation.
If you need a lossless intermediate, I'd suggest using an image sequence. PNG or DPX are lossless for 8bpc or 16bpc. OpenEXR can be lossless at any depth (although it defaults to half-float whereas Ae uses 32bpc, potentially leading to very small precision differences), and TIFF and PSD are also lossless at any depth.
If you are working at 16bpc or 32bpc and want to preserve the extra depth, make sure your output module is set to Trillions of Colors for 16bpc or Floating Point for 32bpc.
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