If you change the brightness/contrast in the L/Lab channel, you don't change any of the color information.
Aimpoints are key
By establishing neutral aimpoints, you can virtually guarantee that color will reproduce without displeasing color casts.
The highlights should contain the smallest possible dot that will print. Shadows should aim for a total maximum ink coverage of:
Coated Paper - 290%
Uncoated Paper - 270%
Newsprint - 250%
Two Rounds of Sharpening
In Lab (L-channel) to compensate for softening that occurs when scanning
After finalizing and sizing photos
Not usually a good idea to sharpen in all channels at once.
In RGB, sharpen Red and Green only.
In CMYK, shapen Cyan and Magenta, but don't sharpen Yellow. It contains too much noise, and sharpening yellow makes the image look worse.
"Sharpen the heck out of black."
Unsharp Mask Guidelines
Amount - 50 Ð 250
Radius - .5 Ð 2
Threshold - 0 Ð 20, 30
Scans from cheaper scanners require higher threshold settings
Color Correction Cheat Sheet
Five Correction Areas
Analyze tonal values - tonal range compression will remap what can be seen by the human eye into what is acheivable in the CMYK gamut (what can be printed)
Use Image>Adjust>Threshold to determine where the highlights and shadows are in your image.
Neutral Gray Aimpoints
RGB: 245R, 245G, 245B
CMYK: C5, M3, Y3 (Add 2% to Cyan since it is the weak ink.)
RGB: 10R, 10G, 10B
CMYK: 70C, 60M, 60Y, 90K
Caucasian - rule of thumb is that cyan should be about 1/5 to 1/3 the strength of the magenta, with yellow and magenta being at least equat or 5% to 10% more.
Light-skinned / 8C, 40M, 40Y
Medium complexion / 15C, 50M, 55Y
Visibly tanned complexion / 20C, 55M, 60Y
African American and Black (W. African) - increase proportion of cyan to magenta. Of all racial makeups, has the greatest diversity in color.
Hispanic - increase amount of cyan and yellow, and frequently magenta.
Asian - increase proportions of yellow and cyan to magenta. Often similar to dark-skinned Caucasians. Of all the racial makeups, has the least diversity in color.
Sharpening using unsharp masking
All scans need to be sharpened using Filter>Sharpen>Unsharp masking
Don't be confused by the name, "unsharp." The purpose of the unsharp mask filter is to sharpen the appearance of the image. It works by combining a slightly blurry (unsharp) version of the image with the original. In the resulting image, the filter causes the contrast to increase on edges where light and dark areas meet while ignoring areas where there is little change in contrast, leaving smooth and subtle transitions in low-contrast areas.
Radius - sets the width of the unsharp mask halo. Set this before setting the Amount and Threshold. A larger halo creates a more obvious appearance of sharpening.
Amount - controls the intensity of the halo
Threshold - increasing this value minimizing scanner-induced noise in shadow areas. Tells Photoshop how far apart tow pixel's tonal values have to be on a scale of 0 to 255 before the unsharp mask filter affects them.
Strengthen definition in weak image
Apply Image from one channel to another by copying and pasting in normal mode--change mode to "darker" to apply only where source image is darker than destination image. In this way, you can "borrow" the tone from any channel to intensify a weak image.