‘The Photoshop book for Digital Photographers’ by Scott Kelby

H
Posted By
Herman
Jul 9, 2003
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I recently had the opportunity, to take a look at Scott Kelby’s book "The Photoshop book for Digital Photographers".

In the chapter on color correction he describes the use of curves. He sets the default RGB values for the Black point to 240, the RGB values for the White point to 20 and the RGB values for the Gray point to 128. Next he describes the use of the Color Sampler Tools (set to 3 by 3 average) to set these points.

As a trick to find the darkest/lightest areas in an image he uses a temporary Threshold adjustment layer. This way you’ll have a visual clue in finding the shadows and highlights.

As there is no similar trick for the midtones, he suggests to set the color values to display ‘Total ink’ (in the Info palette) and to use the eyedropper tool to find an area whose ‘Total ink’ reading is 128 and use that area for the midtone.

Now I’m a bit lost here. This ‘Total ink’ reading of 128, matches the RGB values for the Gray point. However, the ‘Total ink’ reading is a percentage, black = 300%, white = 0%, 50% gray = 145%. If he is trying to find a percentage matching the RGB values of 128, this ‘Total ink’ reading percentage should be 145-146% instead of 128. Am I missing something here?

Kind regards,

Herman
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John Tee
Jul 9, 2003
Herman,

I haven’t read a serious Photoshop book yet that doesn’t contain errors. I suspect the authors grow tired of their own verbosity and lose concentration in the proof checking. I think the fact that you can recognise errors in the book means that it’s really teaching you about the subject. You are correct – 127 or 128 is the correct value for midtones if you have neutral midtones.

I have the book you speak of, but haven’t read it yet as I’m currently making my way through "Photoshop Color Correction" by Michael Kieran. He recommends RGB values of 245 for the highlight in an image, and 10 for the shadow point. (The values you quote are back to front – white is 255 and black is 0 in RGB.)

The values you choose depend on your output for a particular image, and you might adjust it differently for the web or for print.

The recommended values of 240 and 20, or 245 and 10 neglect to explain why these might be reasonable values to aim for. I correct my images to 255 (total white) and 0 (total black) because I understand the Zone System. And I understand how it relates to Curves. I thought I must be the only person the world who understands this, as I’ve read so many Photoshop books that never mention the relationship – that Curves can be displayed with 11 grid lines which correspond to the 11 values in the Zone Sytem from 0 to X.

However, Photoshop 7 Artistry explains it well.

I’m not familiar with CMYK. But as I understand it, you should not be looking at total ink values (except as a value not to exceed). You should be looking at neutral values, and these will not be 50C, 50M, 50Y and 50K (according to what I’ve read) but perhaps 60C and 50 for the rest..

I’m no expert, but I hope this helps, and perhaps encourages experts to contribute and set us both straight.

John

On Wed, 9 Jul 2003 10:14:46 +0200, "Herman" wrote:

I recently had the opportunity, to take a look at Scott Kelby’s book "The Photoshop book for Digital Photographers".

In the chapter on color correction he describes the use of curves. He sets the default RGB values for the Black point to 240, the RGB values for the White point to 20 and the RGB values for the Gray point to 128. Next he describes the use of the Color Sampler Tools (set to 3 by 3 average) to set these points.

As a trick to find the darkest/lightest areas in an image he uses a temporary Threshold adjustment layer. This way you’ll have a visual clue in finding the shadows and highlights.

As there is no similar trick for the midtones, he suggests to set the color values to display ‘Total ink’ (in the Info palette) and to use the eyedropper tool to find an area whose ‘Total ink’ reading is 128 and use that area for the midtone.

Now I’m a bit lost here. This ‘Total ink’ reading of 128, matches the RGB values for the Gray point. However, the ‘Total ink’ reading is a percentage, black = 300%, white = 0%, 50% gray = 145%. If he is trying to find a percentage matching the RGB values of 128, this ‘Total ink’ reading percentage should be 145-146% instead of 128. Am I missing something here?
Kind regards,

Herman
TT
Tom Thackrey
Jul 9, 2003
On 9-Jul-2003, John Tee wrote:

The recommended values of 240 and 20, or 245 and 10 neglect to explain why these might be reasonable values to aim for. I correct my images to 255 (total white) and 0 (total black) because I understand the Zone System. And I understand how it relates to Curves. I thought I must be the only person the world who understands this, as I’ve read so many Photoshop books that never mention the relationship – that Curves can be displayed with 11 grid lines which correspond to the 11 values in the Zone Sytem from 0 to X.

The reason you don’t want your whites to have a value of 255 is that they will look blown out when printed, especially in offset printing. Using a value like 245 or whatever will ensure some dot pattern in the whites.

—
Tom Thackrey
www.creative-light.com

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