I have a QuickTime movie, created with Avid on a PC, using the DNxHD codec. When I open it in QuickTime Player on a PC, the colours are fine, but when I import it into Final Cut on a Mac, the colours are a lot brighter- gamma shift, apparently.
I’m looking at the result on a calibrated broadcast monitor through the HD-SDI output of a BlackMagic card, which I believe means I can’t blame it on the monitors.
Changing the User Preference for how RGB video is handled gamma-wise doesn’t appear to make any difference?
Googling for ‘gamma’ and terms like ‘PC’, ‘Mac’, etc. turns up a lot of frustrated people with gamma shift problems, but I didn’t spot a solution.
How can I get this DNxHD into the Mac with the correct gamma?
Hi Stuart, what kind of broadcast monitor are you using? A CRT? And are you using the one monitor to compare? Ie. Are you pumping out your Avid output to the same monitor of your FCP output and doing the compare there?
The Avid is off-site. On-site we have the Final Cut system, and we have one Panasonic calibrated LCD monitor, sadly it’s not a CRT or grade 1.
I have ProRes and DNxHD clips of the same thing on the timeline. When I switch from a frame in one clip to the same frame in the other clip, there is a very visible difference between the two. The DNxHD version is brighter and ‘milky’.
I’ve tried exporting DNxHD from Final Cut and it has the same problem as the DNxHD sourced from the Avid.
So it’s looking to me, in this instance, that whatever DNxHD file I pull into Final Cut, it’s always looking milky?
Hmmm… Well first off The Gamma Shift of your original file (checked on both a PC and Mac) is due to the difference in Gamma level outputs. Most PC’s show a Gamma level of somewhere between 2.2 and 2.4. A Mac’s default Gamma is 1.8 I believe. Check out this link for furthur reading:
How do you need to deliver your project? If your delivering for the web (where most people view videos on pc) then I would change your mac gamma settings in the mac OS ColorSync control to the value of a PC so that you can view your file (on your mac desktop) as most would see it. Heres a link on how to do it:
Alternatively you could add a gamma correction filter from fcp and adjust it to match the output of your PC (just to see the file as you were seeing it on a PC).
I would strongly suggest checking your file on a CRT as the Gamma output would be very similar to a PC. Its also worth checking your gamma settings on your monitor and video card (if they are adjustable).
As for the Gamma jump between the two files with different codecs in the same timeline I can only assume that the DNxHD codec has a gamma value suitable for PC’s and not macs.
Hope this helps.
Ultimately our delivery is going to be on HDCAM, so it’s the HD-SDI signal (that our Panasonic monitor is showing) that will need to be right. Since that’s a hardware output, none of the ColorSync type monitor settings would make a difference- I think?
The root of the problem seems to be how Final Cut copes with the DNxHD, or rather how it doesn’t cope- as well as being very wrong in the colours, Final Cut crashes a lot when I try to get it to use the DNxHD file. I think we’re going to have to find an alternative workflow that doesn’t use DNxHD.
As a very quick follow-up, it seems that with the DNxHD file we’ve got, using Compressor and going via an uncompressed intermediate file works, while using QuickTime Pro or pulling it straight into Final Cut was causing some bad colour shifts.