Curvemeister Forum

I had some problems with this picture:
1) Do not like picture
2) Bit unclear what to adjust for.

Two questions:
Why are channels named CMYB and not CMYK?
What does wg in wgCMYK stand for?

I tried to increase light in shadows by using two methods 1, decrease CMY and 2, decrease Blacks. For each method I tried three different GCR; light, medium and heavy blacks. Bad results with light black. Tree in left/down corner did not look well. Did I not have enough ink or what happened? I preferred heavy blacks.

Further I noticed if I only changed GCR there was no change in the picture.

Please find enclosed my screen shots on 1 and 2 with GCR=heavy blacks. I prefer 1 as better contrast in picture and colours. But 2 less work.

Thomas

I had some problems with this picture:
1) Do not like picture
2) Bit unclear what to adjust for.

Sorry you do not like the image...It is actually a pretty good example for CMYK adjustments....
You really want to adjust for the best color and shadow controls.  CMYK is a more subtle adjustment space. you might find it to have the feather lite touch you want instead of the hammer like approach LAB can have.

Two questions:
Why are channels named CMYB and not CMYK?
What does wg in wgCMYK stand for?

The Standard for CMYK is to name the channel "K"  Mike probably chooses to use the term "Black" in the curve window because of the differences between wgCMYK and CMYK.  Think of them as flavors of the same process.  CMYK is chocolate and wgCMYK is more chocolate....

The wg stands for "wide gamut"  the gamut or "range" of colors possible in wgCMYK is bigger and there are some colors in wgCMYK that might not print as well when you get to a printed profile.  Not 100% sure of all the technical details but, I'm certain Mike can explain it further if you would like...I think there are some equations and diagrams that help....

I tried to increase light in shadows by using two methods 1, decrease CMY and 2, decrease Blacks. For each method I tried three different GCR; light, medium and heavy blacks. Bad results with light black. Tree in left/down corner did not look well. Did I not have enough ink or what happened? I preferred heavy blacks.

Further I noticed if I only changed GCR there was no change in the picture.

Please find enclosed my screen shots on 1 and 2 with GCR=heavy blacks. I prefer 1 as better contrast in picture and colours. But 2 less work.

Thomas

Remember that GCR is like a volume lever.  The heavier the GCR the less adjustment for the same effect.  Heavy GCR is the easiest to see on the monitor.  The printed results...well actual mileage may vary....

When you add more CMY without changing the K you get the same values but the shadows look incomplete, muddy, or somehow lacking in POP.  If you had to you could make an adjustment without the K but it would take a great deal of CMY.  I'm trying to think of a better analogy....how about this...

If you are making a color print in the darkroom, you always use only 2 colors on the enlarger. You use  Y and M, if you add C you have to zero out one of the other two because otherwise you make neutral gray and the prints look muddy.  the same is true here.  You are adjusting "inks" to print a subtractive image on paper.  The inks subtract light from the reflected white of the paper.  Every place that should be black or dark gray would need some K to complete the "blackness" otherwise too much light is allowed to reflect through the inks as they are semi transparent.

RGB on the other hand is additive.  The colors combine together to create white.  255,255,255 = white and  0,0,0 = Black.  I always think of RGB as theater lighting you can add Magenta and Green lights and get a neutral light that appears white to the eye.

Great questions...If I have not answered you or I provided answers to the wrong questions...I hate typed responses sometimes...Please let me know...I'll try another approach...

Greg

BTW your second image was the better of the two.  The details in the wreath, flower petals, and such stood out more in that version.  You could go even further in the parts of the K channel that add details to the wreath petals....remember you do not have ink limits so you can go as far as you like....

Greg