Working with duotones.
Photoshop is useful for converting images into duotone. This can make printing a lot cheaper as it can limit the number of Pantone inks needed to print. This will end up reducing the overall cost of a print and is therefore very useful within commercial graphic design. The steps on how this can be achieved can be seen above. This will be helpful for me if I ever forget how to convert an image into duotone.
Working with the channels panel.
You can also reduce print costs by getting rid of certain colours in the channel path. You can remove channels and completely change the colour to Pantone colours as you can see above. This is also how you set up a document to be commercially UV spot varnished.