Most of the time you will be using a photo or scanned image.
When opening a new file you can change the resolution.
You don't get a higher quality resolution than 300dpi when printing for commercial print.
The default colour mode is RGB (design for screen) which has a different colour gamut (range) so some of the colours wont be printable.
Also working in CMYK colour mode when working in photoshop restricts some of the options so you don't get the full potential of the software. So it's best to work in RGB while editing and preparing and then convert in CMYK before saving. You can do this by going to image/mode/CMYK.
One of the down sides to working in CMYK is that the files are larger than RGB files.
When applying colour you can click on the foreground and background colour swatches in the tool bar to change the colour your using. You can change the hue and tint to your colour or you can even type in the percentages.
After converting you colour mode to CMYK there will be a change in the colour on the screen, this is really important because you may send something to be printed and it will come back completely different in colour if you don't check it.
To check which colours are not printable go to view/gamut warning. You will see the colours turn to grey and if you were to print the image those colours will be shifted into the nearest printable colour.
You can adjust the image by going to image/adjustments and the selecting which one you would like to use. To help change the colours that are grey to colours that are printable by using a hue and saturation sliders. The saturation needs to be reduced until all the grey is gone.
The replace colour tool does a similar thing to the hue and saturation tool but works like the magic wand tool. You select the grey area that you need to change and then use the slider to adjust it. This tool focuses on that specific area that you have selected.
The gamut warning is something that you use just to check the colour when your doing your adjustments.
You can use the proof colours option in the view menu to check your colours and give you a preview of how the image will look in CMYK colour mode. You'll notice that the title bar of the file will change from (RGB/8) to (RGB/8/CMYK).
Creating new swatches in photoshop
You can hold down the alt key and delete the default swatches before making your own.
To make your own click on the foreground colour picker and from there you can select your own colours. There will be a little warning sign that will pop up next to the colour preview next to the colour picker that signifies that the colour you have selected is out of the printable gamut.
Once you have to colour you want to simply click 'add to swatches' and you can name your swatch if you need to.
Another way to add a swatch is to select a colour for your foreground colour and then click in the grey space on the swatches library to create a swatch form it. This is a good method if you want to make a swatch of a colour thats already in the image your working with.
SPOT COLOUR
Good for economic design and highlighting parts of images.
Go to your foreground colour picker and select colour libraries. Here you can select a specific colour and colour book which will work best with the type of stock your printing on to.
If you have a reference number from a client of from a book then you can type it in and you will automatically jump to that particular swatch.
Once you have the colour you need your foreground preview box will change to that colour.
Applying the colour.
create a selection box and then fill it (shortcut alt+delete)
For spot colouring you need to apply it to a grayscale image. You can convert a full colour image to grayscale in the image/mode menu.
To apply the colour and replace the black with the colour you go to image/mode/duotone then select the black swatch and the colour picker will pop up, from there go to the colour libraries and select the colour you want to swap the black with. Thats the way to create a monotone image. Once you click ok it will change the title bar to (monotone/8).
You can add a second colour by changing the setting to duotone in the duotone window. This allows you to mix colours with each other to get new ones. Also you can change the contrast between then by click on the swatches with a diagonal line through them.
Channels
Every image has a channel or channels. RGB has red green blue and but grayscale has just black. Each RGB channel is black and white but the change to represent how much of that particular colour is in that area, black means there is a lot, white means theres is little or none.
You cansave a selected area by going to select/save selection. This is useful if you keep having to go back to a certain area and saves time. The selection can then be accessed in the channels palette, the white on the channel is whats being selected and the black is whats left.
Then you need to go to the palette menu and select new spot channel, this will automatically apply your last colour used but you can change it with the colour picker and libraries by clicking on the swatch in the spot channel window. The colour when printed will overprint the black ink underneath, making the colour transparent.
If the coloured area is too jagged or covers something you don't want it to, you can edit it and erase parts of it on the spot colour channel. This wont alter the image underneath.
You can also create spot channel gradient by creating a new spot colour channel and using the gradient tool. You can manipulate the spot colour channel using most of the standard tools in the tool bar.
You can use spot colouring on a full colour image however it means you will be applying 5 colours to that area, this will cause the paper to get an excess of ink and become ink and it may make all the colours underneath smudge together.
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