Mixing rec709 with Redspace gamma

[Peter Belanger]

Can someone tell me if it's not a good idea to use rec709 but redspace for gamma? Will this cause problems? (REDCINE)

Forgive my ignorance, but what's the difference between color space and gamma space?

My DOP is telling me that rec709 has truer blues and greens, but that's using rec709 space and redspace gamma.. We will be exporting dpx out of redcine so I want to make sure we're doing it right. Should I be using redspace/redspace for dpx out.. and let color correction handle it from there?

My head is spinning.

Any help, or explanations will be greatly appreciated.

 

[David Collard]

Color Space: Any method for representing the color in an image.
Based on that definition I would say that Gamma space is any method for maximizing the bit depth of an image. It is often applied as a curve, but it should be done according to what degree you visually want to extract information from your image. It's esthetic.

Rec709 is a broadcast specification for HD. So, if you use Rec709 as your reference for gamma and color space when doing HD post production, you can be assured to keep your colors space within broadcast specifications.

Your DOP probably meant that REC709 as the guideline would give you "truer" colors in terms of using it as the baseline for your broadcast specifications. He didn't mean it would extract truer colors, only that it would be a proper guideline for HD post.

Having said that, if you're going to HD as your final for your client, I would suggest staying in REC709. However, I believe if you're outputting to DPX files for another system it might make sense to keep everything in REDSPACE. This should maximize the information that you've recorded without applying any REC709 compliance specifications to your file. Your editor could always follow REC709 when editing in HD post to a HD waveform/vectorscope, but he/she will have received DPX files that contained ALL the color information that you recorded without having applied any image processing in the first place. Red doesn't apply any image processing to the files per se, but it lets you decide how to handle the files after recording.

Hope I've helped a bit and please correct me if I'm wrong.

 

[Graeme Nattress]

For colour space, cameraRGB and REDSpace are great. Choose which you like the look of. For gamma, use REC709 for a low contrast image for further grading, or REDSpace if you need a quick "looks nice" grade.

 

[Peter Belanger]

That does help.. thanks..

 

[Michael Lindsay]

DO as Graeme says.. great advice!

What I would add is 'do not use' colour space Rec709 unless you have fully tested it.

Shoot a colour chart to help you judge...

kind regards

Michael L

 

[Antoine Fabi]

I have got the best results by filming and editing in REC709 gamma space, with a light s curve in camera to start with, to encourage me to to gently open the aperture and compress the highlights without blowing them.
Also, i have had better success with Camera RGB than REDSpace for color space.
I have difficulties with the color darkening effect of RedSpace color space, specially the reds, they look too dark and saturated for my taste. Camera RGB color space is always easy for good balance between colors.

What i've never had success with is REC709 color space.
...leads me to ask...what may i do wrong ?
I can't get true orange color without shifting every other colors.
The colors are extremely vibrant, and the saturation must be tamed, it's pleasing but i can't get good balance.

Thanks

Antoine

 

[Michael Lindsay]

What i've never had success with is REC709 color space.
...leads me to ask...what may i do wrong ?

I'm not 100% but I think you are doing nothing wrong.. Stick a colour chart up and REC709 makes a mess of it... I've asked numerous times about this on this forum and the silence coming back makes me think it is probably being worked on. (the tricky bit is that the HDSDI out uses the rec709 colour matrix)

I also think it is a great idea to have a little curve loaded in the camera to encourage correct exposure and not reliance on deep and therefore a bit noisy blacks.

I also think that it is worth creating camera curves for different lighting situations rather than using ASA.

For example I have a low light curve that delivers a 800asa shooting style but stops you using too noisy blacks. The curve actual works off 250asa setting so you know if you've blown a highlight.

Its great that Red is offering these options and when the colour weirdness is sorted I feel it will be unbeatably flexible..

regards

Michael L