decrease contrast in color zone system is wrong

telperion · **Joined:** Oct 11, 2014 **Posts:** 82

Attachment:

zonesystem.jpg [ 191.67 KiB | Viewed 4264 times ]

for contrast value <1.00, the contrast don't decrease but increase..

Zero01 · **Joined:** Jan 06, 2017 **Posts:** 204

Could be an optical illusion... (?)

telperion · **Joined:** Oct 11, 2014 **Posts:** 82

Optical illusion?

Attachment:

contrast.jpg [ 119.74 KiB | Viewed 4234 times ]

Wallace · **Posted:** Thu Oct 19, 2017 10:00 am **(#4)**

Have you tried calibrating your monitor,
to see if this has any effect?

dinasset · **Posted:** Thu Oct 19, 2017 10:23 am **(#5)**

It looks like that filter works that way, strange, probably in that context "contrast" means something different, IDK.
Wait on David.

dinasset · **Posted:** Thu Oct 19, 2017 10:41 am **(#6)**

The funny thing (for me, because I do not know what it's behind that filter) is that the contrast (in the image) is increased both if you set a value < 1.0 and a value > 1.0 (in the contrast parameter).
An explanation is certainly needed.

telperion · **Joined:** Oct 11, 2014 **Posts:** 82

dinasset wrote:

The funny thing (for me, because I do not know what it's behind that filter) is that the contrast (in the image) is increased both if you set a value < 1.0 and a value > 1.0 (in the contrast parameter).
An explanation is certainly needed.

Same for me,
gamma too, works in "mysterious way"...

telperion · **Joined:** Oct 11, 2014 **Posts:** 82

the original code is:

Code: Select all

#@gui Zone system : fx_zonesystem, fx_zonesystem_preview(1)
#@gui : Shadows zone = int(1,1,5)
#@gui : Highlights zone = int(10,6,10)
#@gui : Gamma = float(1,0,5)
#@gui : Contrast = float(1,0,4)
#@gui : Black point = int(0,0,255)
#@gui : White point = int(255,0,255)
#@gui : sep = separator(), Preview type = choice("Full","Forward horizontal","Forward vertical","Backward horizontal","Backward vertical","Duplicate top","Duplicate left","Duplicate bottom","Duplicate right")
#@gui : sep = separator(), note = note("<small>Author : <i>Tom Keil</i>.      Latest update: <i>2011/13/02</i>.</small>")
fx_zonesystem :
-repeat $! -l[$>] -to_rgb -rgb2lab -s c -n[0] {{$1-1}*10}%,{$2*10}%
-a c -lab2rgb -tk_fx_channel_processing $3,$4,0,0,0,0,100,256,0,0,0,2,7,0
-fx_apply_curve 0,$5,0,$6,255,-1,128,-1,128,-1,128,255,1,7,0,0,0
-endl -done
fx_zonesystem_preview :
-gui_split_preview "-fx_zonesystem ${1--2}",$-1

the -tk_fx_channel_processing is the problem.
Replaced with fx_channel_processing:

Mc Zone system

Code: Select all

#@gui Mc Zone system : mc_fx_zonesystem, mc_fx_zonesystem_preview(1)
#@gui : Shadows zone = int(1,1,5)
#@gui : Highlights zone = int(10,6,10)
#@gui : Contrast = float(0,-100,100)
#@gui : Gamma = float(0,-100,100)
#@gui : Black point = int(0,0,255)
#@gui : White point = int(255,0,255)
#@gui : sep = separator(), Preview type = choice("Full","Forward horizontal","Forward vertical","Backward horizontal","Backward vertical","Duplicate top","Duplicate left","Duplicate bottom","Duplicate right")
#@gui : sep = separator(), note = note("<small>Author : <i>Tom Keil mod by Telperion</i>.      Latest update: <i>2017/22/10</i>.</small>")
mc_fx_zonesystem :
-repeat $! -l[$>] -to_rgb -rgb2lab -s c -n[0] {{$1-1}*10}%,{$2*10}%
-a c -lab2rgb 
-fx_channel_processing 0,$3,$4,0,0,0,100,256,0,0,0,2,0,0
-fx_apply_curve 0,$5,0,$6,255,-1,128,-1,128,-1,128,255,1,7,0,0,0
-endl -done
mc_fx_zonesystem_preview :
-gui_split_preview "-mc_fx_zonesystem ${1--2}",$-1

and now contrast and gamma works as expected.

Attachment:

zonemod.jpg [ 52.07 KiB | Viewed 4098 times ]

dinasset · **Posted:** Sun Oct 22, 2017 7:05 am **(#9)**

Good finding!
Send a PM to David (Tschumperlé)

telperion · **Joined:** Oct 11, 2014 **Posts:** 82

@dinasset

maybe could be better:
adjust shadows, highlights, black and white points,
and then eventually adjust contrast and/or gamma.
What do you think?

Code: Select all

-repeat $! -l[$>] -to_rgb -rgb2lab -s c -n[0] {{$1-1}*10}%,{$2*10}%
-a c -lab2rgb
-fx_apply_curve 0,$5,0,$6,255,-1,128,-1,128,-1,128,255,1,7,0,0,0
-fx_channel_processing 0,$3,$4,0,0,0,100,256,0,0,0,2,0,0
-endl -done

dinasset · **Posted:** Sun Oct 22, 2017 8:32 am **(#11)**

It could be, but again detail your suggestion to David (the author), I do not use (any more) G'MIC for my image manipulation, I was just experimenting with this filter to confirm your submitted problem.
Thanks for your consideration and sorry for not following you further.

telperion · **Joined:** Oct 11, 2014 **Posts:** 82

added an optional color temperature correction

Code: Select all

#@gui Mc Zone system3 : mc_fx_zonesystem3, mc_fx_zonesystem3_preview(1)
#@gui : Shadows zone = int(1,1,5)
#@gui : Highlights zone = int(10,6,10)
#@gui : Black point = int(0,0,255)
#@gui : White point = int(255,0,255)
#@gui : Contrast = float(0,-100,100)
#@gui : Gamma = float(0,-100,100)
#@gui : color adj = bool(0)
#@gui : Color temperature = float(0,-20,20)
#@gui : sep = separator(), Preview type = choice("Full","Forward horizontal","Forward vertical","Backward horizontal","Backward vertical","Duplicate top","Duplicate left","Duplicate bottom","Duplicate right")
#@gui : sep = separator(), note = note("<small>Author : <i>Tom Keil mod by Telperion</i>.      Latest update: <i>2017/22/10</i>.</small>")
mc_fx_zonesystem3 :
-apply_parallel "
-to_rgb 
-rgb2lab -s c -n[0] {{$1-1}*10}%,{$2*10}% -a c 
-lab2rgb 
-fx_apply_curve 0,$3,0,$4,255,-1,128,-1,128,-1,128,255,1,7,0,0,0
-fx_channel_processing 0,$5,$6,0,0,0,100,256,0,0,0,2,0,0
-if {$7==1}
   -fx_mix_lab 1,0,0,1,{if({$8>=0},{$8/4},{$8*0.75})},0,1,$8,0,0,2,0
-endif
"
mc_fx_zonesystem3_preview :
-gui_split_preview "-mc_fx_zonesystem3 ${1--2}",$-1

Attachment:

zone3.jpg [ 65.8 KiB | Viewed 2300 times ]