Glow and temp/tint question

Skip to first unread message

Nov 15, 2021, 1:29:46 PM11/15/21
to SCRATCH forum
Hi everyone,

Two short questions :
1/ I was wondering if there was a way to change temp/tint without affecting the luma.... (and without going on a separate layer with a color only blending mode). Let me know if I am wrong but it seems to me that temp and tint react just like gain adjustment on two different axis.... and so luma seems to be affected by every change....

2/ What is your favorite glow shader effect ? The assimilate Highlight bloom works but if there was a little more complex one in the repository... I'll be happy too.

Thanks in advance,

Best regards,

Nov 17, 2021, 1:54:22 PM11/17/21
to SCRATCH forum
Hi everyone,

Just bouncing on my own two silly questions :-P
Just found on the manual that regarding temp and tint : " With any adjustment of these parameters SCRATCH attempts to maintain a constant luminance for the image." \o/
Indeed, the different color channel are compensating when adjusting these settings, and yet there is a slight difference in luminosity (mostly when the adjustment is pretty high. It is visible when you make an adjustment on a specific layer and switch this layer from normal to color blending mode : warmer temp goes darker, cooler goes brighter).
Perhaps there is some intrinsic limitation to the accuracy of the compensation ?
Anyway, on that YRGB stuff I was also thinking that a "luma mix" slider could be a great thing even for other RGB adjustments... or is there a tip for that parameter already ?


Tobias Wiedmer // Cine Chromatix KG

Nov 17, 2021, 2:28:54 PM11/17/21
Hi Alex,

for real white balance adjustments you need to do it colourspace aware->gain adjustment in linear (you have to convert properly and you need an inverse tonemapping in case you come from a display referred space)  or offset in log space (best case scenario ACES CC, not ACES cct).

if you want to avoid any luminance shift, you could build a matchbox shader which keeps it constant by comparing lumiance before and after the adjustment. Don’t know if that is very useful, though.

maybe that helps,

Tobias Wiedmer, CSI
Lead Colourist / Colour Scientist

Cine Chromatix KG 
Goethestr. 85 
10623 Berlin 
Tel: +49 (0)30.327 805-97 
Fax: +49 (0)30.327 805-90 
Vertreten durch die 
Geschäftsführer: Janosch Benz, Ufuk Genc 
Registergericht: Amtsgericht Berlin-Charlottenburg 
Registernummer: HRA 39272B 
P before printing this email, think about the environment

ASSIMILATE homepage -
Facebook -
Twitter - @assimilateinc
You received this message because you are subscribed to the Google Groups "SCRATCH forum" group.
To unsubscribe from this group and stop receiving emails from it, send an email to
To view this discussion on the web visit

Reply all
Reply to author
0 new messages