Interesting discussion indeed, Ida.
Always interesting to see how others look at image quality and do their post process.
I start to believe that the anamorphic 5.7k raw on 5D3 is a true 5.7k raw with a compression ratio of 6 or above, as the horizontal binning has a compression ratio of 3 or above, and the 14-bit lossless LJ92 has a compression ratio of 1.5-2.5, depending on scene complexity and ISO level. The image quality may be "mediocre" comparing to the native uncompressed 6k raw, but should be much better than 1920x2340 if AR is 2.40.
Currently, Red Komodore has a 6K raw with compression ratio choices of 3 to 12, the same as the BMPCC 6K Pro. If implemented the same as the Canon R5, Canon 1DX3 and C500MK2 have 6k raw with a compression ratio of 6.
...
...
My bet is that all of these cameras will be similar in terms of image quality if not pixel peeping, as long as the operator is an expert on the camera and on the raw process to release the full potential of the system.
In terms of resolution, the 5d3 and other ML cameras will never win in anamorphic modes, on resolution/detail that is.
The other cameras don't use pixelbinning or lineskipping as technique to lower compression rates.
The biggest digfference between these professional video cameras and the 5d3 and other canon DSLR's is the readout speed of the sensor.
The ML cameras can't readout fast enough to read enough pixels for 4K.
For example, the 6d sensor can be read out at a speed of about 90 megapixel per second.
UHD 3840x2160 x 24(fps) = about 200 megapixel per second...so not possible on 6d (that's the reason why highest crop mode on 6d in 25 fps = 2880x1200 which is about 86 megapixel per second)
The 5d3 sensor has the fastest readout speed of all ML cameras, that's why it has higher resolutions available in crop and anamorphic modes, but still not fast enough to readout 3840x2160x24fps.
But how these 6:1 compression ratio's work is a bit of a blackbox.
My bet is that most detail is cut off in dark(er) areas of the image.
Still also not sure how raw the BRAW of the blackmagic cameras is, or how raw the CRM files of the Canon 5dR are.
Blackmagic used to have raw cinema dng, which is as raw as raw gets.
But the more you read about BRAW, the more it sounds like a video codec, some say the image is already debayered in BRAW
What is also a mystery to me is canon cinema raw light format (which is the only raw format in the Canon 5dR).
Cinema raw light has a high compression rate and there are no software tools available to extract a raw image sequence out of it.
Which is weird, if I buy a camera that shoots raw, I'd like to be somehow able to extract an image sequence out of the files in a raw format, like CR2, CR3 or DNG.
Doesn't matter if the CR3 or DNG's are lossy compressed, but I like to open them in different photo and video editors to compare different outputs.
That said ML raw has some pros against the 6:1 compression techniques.
ML raw gives you true 14 bit lossless raw compression. (or lower, like 10 bit if you want to, but still lossless compression)
So color detail and shadow area's are probably better compared against 6:1 compression techniques.