The Animation CODEC is capped at 8 bits per channel (or millions of colors). If you switch to GoPro Cineform 4, Uncompressed YUV 10-bit or Apple ProRes 422, you can get to trillions of colors (16 bits per channel). For floating point (32 bits per channel), I've always understood that you have to switch to a still image format that supports that and render an image sequence. You're on Windows, right? Try GoPro Cineform 4 or 5 (five is the highest setting). One of the many challenges of working at a very deep color depth is having to wrestle with a what the picture looks like when the color depth inevitably gets reduced. For what it's worth, "Use maximum render quality" is specifically for when exporting from Premiere Pro and you've scaled source footage below 100% allowing for finer detail in the reduced picture. If going the Image Sequence route, I'm 99% sure that OpenEXR, Radiance and TIFF are the only three still image formats that will go as high as floating point (32 bits per channel). Targa seems like it might, but when you see "32" for that format, that's 32 bits per pixel which is 8 bits per channel. Of course, none of these are video formats.
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