Ron Michaels wrote:Why is grading on a computer display connected directly to a gpu so inaccurate (aside for perhaps web delivery purposes)? If the entire pipeline is say 10 bit from software to display, and the display is calibrated to rec709, what is the issue? Is it video/data levels or something to do with grading in a rgb color space, all of the above or more? Again, my apologies for the newbie questions....
If you use the same good monitor then it's not (
OR IT DOESN'T HAVE TO BE) less accurate at all.
Issues are on the software side, which are in most cases not written to give accurate GUI preview.
If you use software which has been written this way (using e.g. OpenGL surface), like Scratch then accuracy is even better as data is always 4:4:4 and doesn't have to go through any RGB<->YUV conversions. GPU pushes data directly to display over DP or HDMI, where in case of SDI card data has to be first converted to one of the supported pixel formats (quite often this is YUV 4:2:2) and than card pushes it to the display (which has to convert it back to RGB). There is also less delay and overall system resource are less stressed in case of GPU monitoring.
Look at printing industry- do they use SDI preview? They can produce accurate prints which are quite often even more difficult to achieve than video preview.
Whole thing is a legacy issue and laziness (and deliberate politics) of companies which in most cases have no interest to implement this as they (or their "friendly partners") make money on selling SDI hardware. SDI is good when you need long distance cables, but for private studio DP or HDMI is at least as good.
Once you have formed correct RGB data then fact if it travels over SDI or HDMI/DP makes not much of a difference. It's digital world, so if the data which left GPU is correct then it can be 100% the same regardless of SDI or DP cable (DP actually offers more bandwidth, but shorter cables). Key point here is to make sure that data which leaves GPU (in other words- hits DP/HDMI cable) is CORRECT. There are ways of achieving this, by separating from OS color management engine (eg. using OpenGL technology).
Today consumer technology in some case is more advanced than pro, which use to never be the case old days. Things are changing and you have to adapt/follow it or you will have hard time to survive.
Resolve is just not one of these tools, specially on PC.