Expert: LizaL - 7/3/2006

Question
Hi there.
I'm using Photoshop CS on a PC.
I have a grayscale image and I want to run a colour strip across it. The strip should not be completely opaque, ie I basically want that part of the image to be seen as if through, let's say, blue cellophane. If that isn't a too idiotic way of describing it. Is there any way of kind of keeping part of the information as grayscale and only that one bit as cmyk colour? Because I don't like how cmyk conversion makes my grays look. So kind of have an image that has two colour modes at the same time? (Assume that I am a moron... I can work the tools and everything but I know very little about all the technical stuff like channels and levels and what not) Thanks.

Answer
Hi Ingrid,

No, that's not an idiotic way of describing what you want to do!! I do believe I understand exactly what you mean. You want a grayscale image with a translucent color band over part of it, right?

That's easy enough to do. But the hard -- and impossible -- part is to make an image have two color spaces. You just can't do that.

But I know a workaround, and it's like this:
1. Open your image, and if it's RGB, make it CMYK (as you'll see me do in my example here in a minute).

2. Instead of making the image grayscale using the Image > Mode command, use Image > Adjustments > Desaturate. This removes all the color from your image.

3. Now make a new layer. Fill it with the "blue cellophane" by filling the area you want to be colored with your desired color, then lowering that layer's opacity.

4. That's it. You now have a (fake) "grayscale" image that's CMYK, and it has your see-through color in it.

Here's how I did it:

http://little-works.com/all_experts/desaturate_cmyk.mov

BUT -- the problems I see here would be that you might be starting out with a grayscale image. If that's the case, then no, there's no workaround that I know that would let you have a true grayscale image, and combine it with a CMYK part.

Another thing would be that desaturating a color image won't really give you a grayscale in the truest sense of the word. It only removes the color information, and doesn't actually regenerate the image into a true grayscale image.

You can see in my example that desaturating the color image I started with makes it look kind of sepia-ish, instead of sharp blacks and contrasts. But you could possibly go in and tweak the Levels and Curves and gain more richness in the dark tones.

So I guess the answer is yes and no! Try this and do some experimenting, and if you need some more help, or you'd like me to go into more detail, please feel free to post back.

Hope this helps!

Lisa