The range of colour that you can produce using CMYK is not as much as the range produced by RGB, also called a gamut of colour.
When switching between RGB and CMYK colour modes, Photoshop will choose the nearest colour that that colour mode can achieve.
RGB is Photoshops default colour mode - it prefers to function in this mode. CMYK files are larger, too!
Converting an image from RGB to CMYK successfully:
This is an RGB image. I want to change it to a CMYK image.
Going to view > gamut warning, displays all the areas that will not successfully translate to CMYK as they are not in that colour range.
Here is the result.
By playing around with the hue and saturation, we can see that the grey area reduces and more is CMYK transferrable. If we use a hue and saturation layer to change the hue and saturation but without damage to the original image. We can then remove the mask on areas that were not needed.
This image has parts of the mask removed on areas that it didn't necessarily need it, to try and get it as close to the original image as possible.
Proof colours
Another way to test working CMYK is to go to view > Proof colours.
What we can see on screen now is what it will look like if we were to convert to CMYK.
Preparing images for press
From Photoshop, you can prepare image files for offset lithography, digital printing, gravure, and other commercial printing processes.
Generally, your workflow depends on the capabilities of the prepress facility. Before you begin a workflow for commercial printing, contact the prepress staff to learn their requirements. For example, they may not want you to convert to CMYK at any point because they may need to use prepress-specific settings. Here are some possible scenarios for preparing your image files to achieve predictable printing results:
- Work entirely in RGB mode and make sure that the image file is tagged with the RGB working space profile. If your printer or prepress staff use a color management system, they should be able to use your file’s profile to make an accurate conversion to CMYK before producing the film and printing plates.
- Work in RGB mode until you finish editing your image. Then convert the image to CMYK mode and make any additional color and tonal adjustments. Especially check the highlights and shadows of the image. Use Levels, Curves, or Hue/Saturation adjustment layers to make corrections. These adjustments should be very minor. Flatten the file if necessary, then send the CMYK file to the professional printer.
- Place your RGB or CMYK image in Adobe InDesign or Adobe Illustrator. In general, most images printed on a commercial press are not printed directly from Photoshop but from a page-layout program like Adobe InDesign or an illustration program like Adobe Illustrator. For more information on importing Photoshop files into Adobe InDesign or Adobe Illustrator, see AdobeInDesign Help or the Adobe Illustrator Help.Here are a few issues to keep in mind when you work on an image intended for commercial printing:
- If you know the characteristics of the press, you can specify the highlight and shadow output to preserve certain details.
- If you use a desktop printer to preview the appearance of the final printed piece, keep in mind that a desktop printer cannot faithfully replicate the output of a commercial printing press. A professional color proof gives a more accurate preview of the final printed piece.
- If you have a profile from a commercial press, you can choose it with the Proof Setup command and then view a soft proof using the Proof Colors command. Use this method to preview the final printed piece on your monitor.Note: Some printers may prefer to receive your documents in PDF format, especially if the documents need to conform to PDF/X standards. See Save in Photoshop PDF format.
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Swatches and Colours
Theres 2 different ways to delete swatches : Either drag 1 at a time to the bin, or hold alt and click to delete a swatch, also one as a time.
When picking a colour, there is indications on what platforms you can use this colour on.
When this warning sign appears, it means it's not available for CMYK - aka design for print.
The cube means it's available for design for web.
You can save this by going to 'add to swatches'. Then in the swatches drop down menu, click 'save swatches'.
If you want the original swatch palette back, select 'reset swatches'
And click OK.
But if you want your 1- colour swatch palette back then go to replace swatches and you'll be able to select your empty palette.
(Note: you can't have a completely empty swatch palette there has to be at least 1)
Pantone swatch books
To find the Pantone colour libraries, go onto the colour picker and go to 'Color libraries'
This screen shall appear. You can type in a number without a text box and it will jump to the colour with that name. Click OK, and you will see that colour in the foreground square - it's ready to use.
If you then wanted to add this to the swatches palette, click any empty space in the swatches palette and it will save it.
But we are still working in RGB with a spot colour. It will change everything on the image to RGB, even with a spot colour used for print. We need a reference number/ name to help us refer to that colour with our printer.
Creating a duotone image
Duotone can only be applied to a grayscale image.
This dialogue box will appear. Select duotone in the drop down box and select the colour.
I have selected a red colour.
However, we usually use Pantone colours for this.
In the same way, go to 'color libraries' to select pantone colours.
Like using the curve tool when editing an image, we can use the curve tool within duotone options.
You can change the duotone options at anytime, even after you've saved (but not exited).
You can add more than one colour depending on what tone you pick:
You can edit both the curve options for both colours in this independently from one another.
There are a lot of useful preset settings in this that make good starting points with legitimate Pantone colour systems:
Different colour channels
In all images, there different colour channels. This depends on the colour mode. If it's RGB, then there's 4 colour channels: Red, green, blue and RGB. In CMYK there's 5: Cyan, magenta, yellow, key and CMYK. In a grayscale image there's only 1: Gray.
This is useful for designing for print because it separates it for different printing plates/ screens.
To create a halftone image in a different technique, go to the channel options and then 'new spot channel'.
You can create a new spot channel according to the magic wand tool, and anything else you can select by selecting it then clicking on new spot channel.
Only TIFF or .psd files support spot colours in the next stage of the process.
