I have an undistorted workflow issue.
The undistorted resolution is an arbitrary value intended to contain the resized bowtie.
However in Flame I can export an EXR sequence at the 2446 x 1702 resolution but not a JPG
When I export a JPG sequence it forces the width to 2448 and does some ugly padding through the centre of the frame.
I took a look at some other formats and it seems to be an 8-bit 16-bit problem. When I export a 8-bit TIF it reformats the width. When I export a 16-bit TIF it doesn’t.
Are there only a set number of resolutions that can be used at 8-bit?
I’ve run into this exact same issue before and came to the same conclusion. I don’t recall the math off-hand but yeah, there’s something about 8-bit images and them having to be divisible by a certain number. Interestingly you have nice even numbers so perhaps it’s related to the aspect ratio.
In the end we went EXRs all the way to avoid such unexpected headaches.
Jpeg uses DCT - based compression math, and because of analyzing data by blocks, JPG pixel size should divide on 8 or 16 (do not remember exactly) - DCT algorythm analyzing data by 16x16 pixels block
UPDATE: So I can export the resolution but if I try and import it at 8-bit it will try and pad the resolution (badly)
If I force the bit depth to be 10-bit I can get the resolution I need. Just a little extra info I have just discovered.
I was trying to find a suitable working resolution. Footage shot on the ArriLF @ 4448 x 3096 and I needed to protect for a vertical resolution of 1920.
Made sense then to do all VFX at the plate resized to 2758 x 1920 except 2758 was getting rounded up to 2760 when ever an 8-but file was used.
Ah! Just one to watch out for. To be honest I have been getting some very funky stuff from 8-bit files recently so I have been promoting them to 10-bit anyways.
Smarter everyday!
I have just watched this video on JPEG compression.
It talks in depth about DCT (Discrete Cosine Transform) and h.264 compression.
