no CMY, just K in images - question

I need to prepare a booklet to be printed on offset in black and white, so, single colour print. (client request, to save money)

I've converted all the images to grayscale, however when I use the colour picker in photoshop to check the colour of image, it is still made of all 4, c m y and k.

How can I turn images into REALLY just K?

 

What software are you using to create the booklet?

You mention PhotoShop's colorpicker - please tell me you haven't created the booklet in PhotoShop

have you tried looking at the image using channels? It may be that although it looks like grayscale it is really RGB.

 

The booklet is imade n InDesign. Photos are edited in photoshop.

The image is most certainly not in RGB.

What confuses me is photoshop's "grayscale" mode. This is my problem. I convert the image to "grayscale", and it has only one channel - "gray", yet when I select a colour and look at its composition, it says, for example:

C 37%
M 33%
Y 38%
K 35%

When I would expect it to say:

C 0%
M 0%
Y 0%
K 80%

Anyway. Since yesterday I've found one trick to remove CMY - I convert back to CMYK, and tick "monochrome" in Adjustments > Channel Mixer. That makes it black & white using only black, however it also ruins the quality of the image, so I'm not totally happy with it.

AND ALSO, when I put such an image into indesign and select a colour from it using InDesign's colour picker, it is again read as

C 37%
M 33%
Y 38%
K 35%

Even though it says

C 0%
M 0%
Y 0%
K 80%

in photoshop??

Now I'm just not smart enough. I don't know. All I want is to make sure that when I make the pdf, the images won't export with grays made of all four colors but only K... is that even possible?? Or... is it actually necessary?

Is it enough to just make it grayscale mode in photoshop and ignore all the color picker nonsense?? I just don't know.

 

Ok try this...in InDesign select the separations preview and check your image from there. Deselect the K channel and then you'll see if there's any CMY elements to the page.

Assuming your pic is true grayscale when you position the cursor over the pic you should only see % of K

You can change the pic mode in PShop Image>Mode>Grayscale

You can send me a sample PDF and I'll check it for you if you wish ...

 

When you create your PDF for final output don't forget to export as PDFx-1a (this being the most compliant file). Don't ignore font warnings ie embedding restrictions. And finally check that your designated printshop is fully conversant with PDF workflows.

 

Just another thought, instead of using the color picker to check colour (which gives cmyk/lab/rgb breakdowns of the selected tone) check the K% within the Info palette. As long as the image is Grayscale in PShop and your text in InDesign is made up 100%k not RGB then all should be well. good luck.

 

I never noticed this palette before! Thanks! Yes, grayscale pictures, in indesign show only K. CMYK show all colours. (annoyingly in photoshop it's vice versa but I think I'm gonna trust indesign.)

Thanks!

 

You'll find that opening the image in PShop if you look at Channels you'll only see a Grayscale channel.