Back to Dye Printing Tricks & Tips
Yes. Easily. And if you didn't intend for that to happen, you may be unpleasantly surprised by the output in offset printing. (Now if you're looking for a duotone or tritone that makes a black and white photo more vibrant, that's a whole 'nuter beastie.)
Take for example this two color flier. It's supposed to be a spot green and black. But when I run it to film, the photograph goes very washed out. Why? Because the provided photograph, though colorless, was actually RGB.
You can see what happens on the film RIP by using InDesign's separation preview.
Turn on "Separations" and you'll see every color swatch it takes to create your current document.
The screen view shows us black text, a green headline, and a black and white photograph. But if we use the separation preview, we can see the photo is actually built from all four process colors (from the RGB file we'll investigate below).
Turn off the cyan, magenta, and yellow plates. Look at that! There's barely any data for the black plate at all! And that's all that's going to image to the film/plate so that's all the ink that will be printed. It looks bad!
Just for fun turn on the cyan and yellow and turn off the black. Wow, the spot green isn't a Panton at all! That's got to be fixed too. Note also the data that now appears in the photograph! There's some of our missing pixels--sent the "color" end of the spectrum. We've GOT to fix that in Photoshop.
In Photoshop we can easily see that the photograph is not grayscale, but RGB. Again in the channels palette we can see how much data is spread over all the color plates to create what seems to be a black and white image.
Go to >Image>Mode and chose Grayscale. You'll get the warning prompt that you're about to delete all the color information (for what it's worth) permanently.
Now you have a real grayscale photo made up of ONLY black dots of various sizes. This will image correctly. (Save that, update the links, and InDesign will put the right image in the right place.)
