RED's Blue is Crimson

[david farland]

Couldn't resist....

Seriously why are saturated blues in Red709 coming out so purple?

Saw a Adam Wilt article in ProVideo Coalition http://provideocoalition.com/index.php/awilt/story/green_magenta/P7/
and thought I'd check for myself.

Shoot a chart (in daylight), import into RedCine, select Redspace/Rec709 & export.

Here's what you get.....& IR filter doesn't make a difference.

Cheers,
Dave

 

[Mark Pugh]

removed...
pending me checking some blue-gelled shots from a shoot last night...

 

[Cail Young]

Should the background field be so blue? I thought it was white or grey on those charts.

 

[Mark Pugh]

Hi Cail
David's point is about saturated blues - so maybe he put a filter or gel over the lens to make his point... the grey neutral card gives an indication of which way the color is swinging.

 

[Mark Pugh]

Looking at the posts here - maybe this is just an Australian phenomenon.

 

[Florian Stadler]

Redspace for Camera Gamma and Rec709 for Output Color space in combination are the problem. Either do Redspace/Redspace or Rec709/Rec709.

 

[Pawel Achtel]

Looking at the posts here - maybe this is just an Australian phenomenon.

Nah, we are just picky b'tards...

Seriously, it looks to me that a skew in colour matrix conversion which, when you saturate, goes too much into red. The way to avoid this would be to saturate first (adjust gamma), and then do the colour space conversion.

 

[david farland]

Maybe leave the 'picky' bit out.

I was a bit soft with the white balance setting yesterday....4pm bit overcast and I left it on 5600K. But I was trying not to exagerate the effect!

Here some pics with WB set where it should be...7500K and colour space/gamma settings as rec709/rec709 & redspace/redspace .
Third image is Redspace with saturation popped up a bit to be closer to 709 saturation

oh dear....Dave,

 

[Pawel Achtel]

Maybe leave the 'picky' bit out.

I was a bit soft with the white balance setting yesterday....4pm bit overcast and I left it on 5600K. But I was trying not to exagerate the effect!

Here some pics with WB set where it should be...7500K and colour space/gamma settings as rec709/rec709 & redspace/redspace .
Third image is Redspace with saturation popped up a bit to be closer to 709 saturation

oh dear....Dave,

It is just a guess, but essentially it looks like colour space adjustment (colour matrix multiplication) happens first in RedCine. This is applied on rather desaturated image. Once applied, it shifts colours by certain vectors (and generally can't be un-shifted) Then, gamma is applied on what was colour-space corrected, but otherwise desaturated image. Thus, the colour shifts go "too far".

The fix could be as simple as reversing the order of processing in RedCine, but practically, I don't know how you could go around it other than simply using different colour space for the time being.

 

[Steve Sherrick]

I have found that using a combination of Rec709 colorspace and Rec709 Gamma provides bizarre shifts that I have yet to figure out. I almost exclusively use Camera RGB or Redspace as my colorspace when outputting in REC709 Gamma.