Workshop: Preparing images for print (Photoshop)

Tab tells you what colour mode you're working in.
All designed to work in RGB, default. 
-Colour Spectrum-
Mode of image should be in RGB, if you change it to CMYK there is a shift in colour (nearest printable colour)

Gamet Warning - silver areas colours are outside CMYK mode

Adjusting the Levels

Hue/Saturation

Proof Colours - The ∆ and exclamation mark shows that it is not a print colour. The cube shows it is not web safe. You can click on them and it will go to the closest colour.

Spot Colour

In offset printing, a spot colour is any colour generated by an ink (pure or mixed) that is printed using a single run. The widespread offset-printing process is composed of four spot colours: Cyan, Magenta, Yellow, and Key (black) commonly referred to as CMYK.

economic factors - cheaper

you can use spot colours to print metallic, fluorescent, varnish colours

Colour Libraries 

The main use of photoshop channels is to store information about colour. Below I have done some experimentation with adjusting them.