Tuesday, 5 October 2010

photoshop colour tutorial

The following are notes from this tutorial:

Photoshop's default colour mode is RGB as opposed to Illustrator with has a default colour setting of CMYK. However, as we are preparing a document to print, we must switch Photoshop's colour mode to CMYK. If you open - for example - a photograph into Photoshop, it will be in RGB mode this is because:
  • RGB mode is for work and documents that are intended to be viewed on screen
  • CMYK is for work and documents intended for print.
This is an example of a green tone in RGB on Photoshop:

And here is the same green after being converted to CMYK (meaning that this is what this colour would look like when printed out in a CMYK printing process.):

Clearly the greens are both very different. This is why it is essential to be careful when selecting colours on Photoshop in the design process. Carelessness results in poor printing.

Here is an image that is 'out of gamut'. In other words, in an RGB mode:

To check whether this image will print in CMYK you can check the 'colour gamut' which will display all areas of the image that will not print as on screen in CMYK. Here is the result:

By changing the hue, saturation and brightness of the image, it is possible to adjust the image for it to be more suitable for CMYK printing. Here is the image and the changed hue and saturation as a way of making it suitable for printing. The gamut warning is still on. There are no grey areas so the image is suitable for CMYK printing:

IMPORTANT - With the colours sorted. You can set Photoshop to work in RGB but so that you can see CMYK colours. This can be done by removing the View Colour Gamut then going to View > Proof Colours.


Colour can be changed using the fill bucket. A colour can be selected for a slected area of the image using the colour picker:

Colours may also be chosen using the swatches.

When using the colour picker, although you are viewing your work in CMYK, it is still good to select colours that can print in CMYK. This exclamation mark tells you that this colour is unprintable. The little coloured square takes you to the nearest printable colour if you click on it:

To create a swatch of your own colour, you go to the colour picker, select a colour then select add to swatches:

Pantone colours can be selected in the drop down menu from the swatches menu for spot colour printing:

You can manually look for a particular Pantone colour by going through the Colour Picker and clicking on Colour Libraries:



To create a duotone image, you MUST begin with a grayscale image. The you go to Image > Mode > Duotone to prepare the Grayscale image:

Then click on the black square and go to Colour Libraries through the Colour Picker and choose a Pantone colour. The image will follow suit in that colour. This makes it MONOTONE:

So you can change the image to a Duotone one by going back to the Duotone menu and adding another colour. You can play with the curve shown in the image to mingle the colours with each other and choose your desired Duotone combination:

This is an advantage as you can use just two spot colours to print a photographic image which can be printed and express a very wide variety of tints and tones.

To select a certain section to fill with a spot colour, you draw around the section you want to fill the select Paths on the right hand margin and then select the dot which is 'Fill path with foreground colour'. And proceed to edit the image:

Here is a primitive edit for the image after following this way of editing:

This concludes the session. I have learnt some valuable information about colouration for print on Photoshop. It is very handy considering the fact that Photoshop is not my strongest program.

Be seeing you!

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