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I am use to working with Coreldraw where I can choose a percent of the color to change the shade but not the color. I have a tshirt design that is two color, but I want various shades of one color to keep within the vendor's "two color" guidelines. I tried duotone, but that changes both of the colors I have on the design. How can I change/adjust the percentage of black (shades of gray) but not the other color (red)?
Hello godmother
This is not an easy task in photoshop. You need to do spot colour separations from a photoshop file, correct. Doutones are great, but fairly limited. You need to start with a grey scale and then select ink colours to apply to the greyscale. And unfortunately other than using tonal curves there is not a great deal of control over where the colour goes. And the real bummer is that you can not paint on colour in certain areas etc and save the edited duotone.
You have a few options.
Probably the easiest is to use two of the CMYK channels to hold your colour info. If you were doing your stuff in red and black, you could use the magenta and black channels. Unfortunately the M channel is a bit brash to look at, but your mind will adjust and you can fool yourself into thinking that is red (just drink lots and lots of coffee). You can preview each sep by selecting the appropriate channel or preview it as a comp in CMYK.
Another way is to use photoshop DCS files to hold the colour info. This is kinda bass ackwards in photoshop. It is great for giving you a preview of the final image in the inks you need to use, but to edit it, you will need to select the channel for that ink and then do what ever you need to do on that channel. I dont think you can use layers, as each ink will be on its own layer... but you will be able to store selections etc in alpha channels.
The easiest way to set up a DCS file (at least from my experimentation) is to create an empty greyscale file at the res and size you need. Convert to duotone (tri or quad) and select your inks. Then convert to multitone. You will end up with a layer for each ink colour. Be sure to check that the back ground on each ink colour is white (or what ever you want) as the conversions to grey and duo sometimes alter this. Then just copy and paste info into the ink layers as needed. Or paint on directly to the canvas. You will not be able to use alot of the photshop effects etc in multitone mode. (see what I said....bass ackwards). If you want your image to be solid red (100%) then the file you copied pixel data from should be black and white. When you paste in your multitone layer...those pixels will show up as 100% of that ink colour. Tints of the colours correlate to tints of greyscale.
You might also want to check how photopaint handles this. From what I remember, you seperated the channels of a duotone image and could then manipulate at will. When done, you recombine the channels (or what ever photopaint calls them). But from my experience with photopaint 5 and 7...this offten does not work properly and I ended up with weird colour shifts. Just another corel bug that rears its ugly head.
Or do the work in a drawing program. WHich will work if you dont need photo images. Type and clipart stuff will work best in this regard.
But once again, you might find it easier to just work in the M and K channels of a CMYK file.
Beth