Cary Knoop wrote:For video (i.e. non-raw footage) if an input color space is defined the chosen timeline color space does not make any change to the look of the footage (it only influences how the controls work).
This is not entirely true. Timeline colorspace has no visible impact (without any grade applied) only when output color space is set. And it is expected because image is transformed from timeline space to output space and changing timeline space does not and should not change the result if these transforms are correct. But when output space is set to bypass, timeline colorspace is effectively the output space and thus changing it will change the result, as expected. Timeline color space does not influence how the controls work (although it might be interpreted as such), controls work the same numerically. But if you apply the same operations on image in different state (which is what timeline colorspace sets), you get different results.
Coming back to original question, these two sets of settings produce the same result for me with no grade applied. With grade they are different as expected, due to reasons outlined before.
What is happening is that in case 1, image is debayered and transformed to BMD Film. As timeline space is the same, no additional transforms are being applied. All grading operations are applied on image in BMD Film state. In the end, transform BMD Film > rec709 is applied. So image data goes through transforms BMD Film > rec709.
In case 2, image starts its journey after debayer as BMD Film. It is then transformed to timeline colorspace: BMD Film > rec709. Grading operations are applied. But as output is set to bypass, image is directly output without any additional transforms. So image data again goes through BMD Film > rec709. Difference between case 1 and case 2 is where the grading operations are done. Case 1: BMD Film > GRADE > rec709; case 2: BMD Film > rec709 > GRADE.