a study in brown...

[ggroess]

GCR stands for Gray Component Replacement.  (Professional Photoshop 5th edition)
It is the base amount of black ink hitting the page in a press printed image.

To get your mind around CMYK you have to remember that the CMY are color complements to RGB; exact opposites....K is the Black ink...K is one of the stronger tools we have in color correction it is extremely useful as we will see in the coming weeks. K gives the image POP and fullness.

In press printing there are limits to the amount of ink you can put to a piece of paper under a given process.  Let's say for discussion the limit is 120   to create an image you not only use CYM inks at various levels you also need to add black...the total of the inks cannot exceed 120 so you might have 20C 50Y 40M this leaves you with being able to add 10K to the mix to darken the shadows and make the overall colors richer.

You could add 3 to each color above to get the same 120 but the shadows would look flat and gray.
GCR gives you control over the amount of K adjustment you are applying to the image. 

So the GCR value is dependent on the material you are printing on and the process the printer has chosen.  You can almost always use Max Black in the class since we are not sending out to a CMYK profile for press printing.

Hope this helps...

Greg

[ggroess]

I moved the blue slider to get rid of the excess yelow. Adjusted the green slider to improve the colour. Then fiddled with he RGB slider to improve the contrast. Opened in PSE and increase brightness +20 and sharpened USM radus 1 at 100%.

I have a question please. What curve would I use that is comparible to the brightness slider in PSE?

Kind Regards

Chris Nicola

Guest for the week

The L channel in LAB is the closest analog to brightness and contrast.  It allows you to adjust the luminosity without effecting color. 

This is one of the primary reasons for using LAB.  You can adjust image contrast and brightness without dealing with color.  Click on the LAB button and then the L channel in the upper center of the window and you will see only the L channel for image adjustment.

See screen shot...
Greg

[mikemeister_admin]

A move from red clay country.More naturalistic and more green in that blade of grass.GregM
Sharpening action set to 40% opacity.The nature of the ground suggests vignetting in the upper corners,someting I had changed in the Lchannel in the first image but left here.Messing with the RGB composite channel  can cause unexpected color shifts.

[imported_BoydMac]

I adjusted the black point to the darkest area of the eye and the light end of the cure to an area that appeared reasonable to me.  It's not clear to me that the image should be a brown as it is do I played with the neutral.  The result is a image which to me appears more reasonable from a color standpoint.  I'm sure further optimization is possible and that we'll learn additional techniques in the coming weeks.  I'm already amazed by what we can do.

BoydMac

[mikemeister_admin]

BoydMac,here is your image with some embellishments.you can control the effect by increasing or holding back the action or c
hanging the layer opacity.
Part I RGB and Lab

[mikemeister_admin]

PartII HSB

I think of the line in the saturation box of the first image as a slope and the second as lifted(or curved)GregM

PS You'll never get in trouble with Greg Groess for too much color.