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Prepress color change need help asap


kimmy1205

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I have a Photoshop file where I have to take a image that has the color cool gray that needs to be changed to black. But I also need to bump the black down so that it looks like it was when it was cool gray. What should I do
 

Tom Mann

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Hi Kimmy - Welcome to PSG!

The hard part of your problem is selecting the pixels to be changed, not the process of changing pixels that have already been correctly selected. The latter is the easy part.

Can you post the image that needs to be changed, or at least a similar one? Without seeing it, we are working in the abstract with respect to selection techniques, and that leaves way too many bases to try to cover. For example, if your cool gray pixels occur in a relatively small number of fairly well defined areas (...like the blacks in a crossword puzzle. or cool gray lettering on a page) then selection tools based on geometry (eg, the pen, marquee, lasso and quick-selection tools) are probably the best choice.

In contrast, if your cool gray pixels are either in lots of small but well defined areas, or in areas with irregular, soft, noisy boundaries (... e.g., whispy cool gray hair against a blue sky background), then selections based on color would probably be the best way to go. Examples of selection techniques that are based on color include the color range tool, using channels to make selections, third party tools like Asiva Select, Vertus Fluid Mask, OnOne's Perfect Mask, Topaz ReMask, etc.

I look forward to seeing what sort of image we will be dealing with.

Cheers,

Tom M
 

Tom Mann

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OK, I get the idea now, but do you have a larger size so that I can use it to show you what to do?

Tom M
 

Tom Mann

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It's difficult to show the selection process with such a tiny image, but I thought that some comments would at least point you in a reasonable direction.

The gray frame in the background of your image can be selected by either geometric methods (eg, using the pen tool), or on the basis of it's weak saturation and light gray tones. If I was doing this for a client, I would probably use the pen tool approach, but this would require almost completely re-drawing the grate. However, since I knew that my example would never be actually used, an alternative approach might be of interest, and performing the selection using Asiva Select would be a lot faster for me, I used that approach.

Here are the curves I used in Asiva Select. As you can see, I selected the weakly saturated areas, without blue-greens, and in lighter (but not white) tones.

selection_curves.jpg

This produced a mask that I used (with a tiny bit of manual clean-up) as a layer mask for a red (for visibility) solid color adjustment layer. The result isn't great, but it isn't bad considering that I started with such a tiny image.

tjm01-ps02a_clean_up_3x-01.jpg

Obviously, if there is any way you can find the original Illustrator or high resolution Photoshop file, that is the way to go, not using after-the-fact, desperation tactics like this.

Hope this is giving you some ideas.

Tom M
 

Tom Mann

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PS - Because links to external sites might break in the future, we prefer that all images for tutorials reside here. So, for those that are interested, here is the (starting) image that the OP posted, at the size it was posted, 200 px wide.
 

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kimmy1205

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Well let me ask you this if the file has a channel that is meant for the cool gray how can I go about editing that color
 

Tom Mann

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From the way you describe it, it sounds like that is a spot color, not a process color. If that is the case, all the printer had to do is change the ink. However, I would check to see if it will turn out the way u expect by first using Photoshop to preview the change before you give the ok for it to be printed with that modification.

Tom
 

Tom Mann

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Hi @HomeShoppingNetwork -

Thanks for your comment, but I'm pretty sure the OP is asking for something different.

From the 1st sentence of the 1st post in your old thread about max black generation, you correctly state, "This is a way to convert a file to CMYK and have things that are black in the original file convert so that they are only on the black plate."

However the OP clearly stated that he something that is gray (ie, not black) in the original that his client wants to change to black, so I don't think the max black generation technique is applicable to his need.

Even worse, since the output of the max black technique still remains a standard 4 plate process, it's not going to give him what his client is really looking for -- fewer plates.

At least I think that's how most of us have been reading the OP's request.

Tom M
 

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