I have two computers sharing the same screens but with different video cards. When I view a video I have uploaded onto YouTube on the different computers (same screens), the video image looks vastly different. (Yes my screens are callibrated)
The problem is that images that look fine on my new expensive editing computer look absolutely dreadful on the other old cheap computer.
If I put a white image over a white background, one white will be true white while the other is darker and yellow making things that should be blended together appear completely different colors and shades. In some cases, objects which are completely invisible on the editing computer are visible on the other cheaper computer.
It seems that the older cheaper graphics (NiVidia Geforce 450) card is showing more detail than the expensive new card (Nividia Geforce GTX 970).
I cannot possibly keep uploading videos & checking them on the other computer each time I make an edit or adjust a color grade.
I don't know if this will be helpful to you or not but I would first do a test to rule out the monitors as the problem because I'm not yet convinced that the issue is with the graphics card or the older computer but let's see.
I'd first simplify your setup for this test and attach each computer to each monitor individually to make darn sure.
1. Old computer to monitor A
2. Old computer to monitor B
3. New computer to monitor A
4. New computer to monitor B
In other words, for this test, don't use the dual monitor setup but go old school so that you can determine where exactly the issue may be coming from.
Thanks for your suggestion. I will try it.
I did discover one more peculiar thing, which is that the variation in colors and shade are increased after uploading to YouTube. It seems that the encryption process used by You Tube does tend to exaggerate the contrast making the variations more prominent.