The colour mode can be instantly found on the title bar or tab of the document.
To change the colour mode;
Image > Mode > Select desired colour mode.
There are colours that you can produce in the RGB colour mode that cant be reproduced with CYMK inks.
'Colour Gamut' is a term that refers to the range of available colours.
RGB is Photoshops default colour mode. Everything you open will open in RGB, make sure you convert any elements to CMYK before sending the outcome to print.
The 'Gamut Warning' option in Photoshop is used to identify colours in an image that are outside of the range of printable colours.
The original image.
Gamut warning applied.
To change the colour levels and retain some control designers can use the Hue/Saturation control panel. Reducing the saturation of the image removes the unprintable colours.
Adjustment layers can also be used to apply a change to a specific area of an image.
Designers can also use proof mode to work in RGB but view the changes in CMYK, this removed the danger of producing unachievable colours.
The tab bar will look like this when viewing work in the proof colours mode.
Moreover, you can also change the settings of the 'Proof Colours' view mode by changing options in the 'Proof Setup' menu.
ADOBE - PREPARING IMAGES FOR COMMERCIAL PRINT
CREATING NEW COLOUR
To clear swatches hold the 'alt' key while clicking on colours in the swatch pattet.
To save a pallet drop down the menu on the swatches pallet and click 'Save Swatches'.
Select the desired location you want the swatches to save to, this will allow you to navigate and find your saved colour pallet.
To load the saved swatches into Photoshop select 'Replace Swatches' and select your saved colour pallet.
When changing a colour open up the colour picker.
The 'Colour Picker' shows options that display if the selected colour is suitable for print, this is indicated by the triangular '!' icon.
By clicking the triangular '!' icon the colour picker will select the nearest printable colour, this is one way to ensure that your colours are within the CMYK colour gamut.
USING SPOT COLOURS
To choose a spot colour open up the 'Colour Picker' and open 'Colour Libraries'. Next, use the drop down menu to select a colour book of spot colours.
Ensure that all spot colours are specified on the print job. The only way a spot colour can be printed is if its reference number is specified.
A photoshop document can only support one colour mode, which means if you work with spot colours in a CMYK document, when they are sent to print all colours will be printed in CMYK.
When creating a duotone image first open a greyscale image.
To start creating a duotone image follow;
Image > Mode > Duotone.
You can use the duotone options menu to change the colours of the duotone image, this allows you to choose spot colours.
Use the colour library to select a colour.
You can also adjust the brightness and contrast of your printed image using the 'Duotone Curve' menu.
Spot colour applied to photographic image.
The ink colour can be changed at any time as duotone leaves the image editable.
A duotone image uses two colours rather than one like the monotone. Selecting duotone in the 'Duotone Options' menu allows gives you the option to use two colours.
These colours are editable in the same way that the monotone colours were.
The same methods allow you to work with tri & quadtones. However, you must bare in mind that using more colours will increase the price of the print job.
There are also pre-set options available that you can select, these will set the colours and their values automatically.
SAVING A DUOTONE
Save As > Format > Photoshop.
Because we are working with a duotone image there are only certain save options available.
DUOTONE IMAGW METHOD TWO
The channels reflect the colour mode of the image, a CMYK image will have four channels. They are the way photoshop stores colour information about each colour of the image.
You can create a new channel by dropping down the menu found on the swatches pallet, this allows you to create a duotone image.
All spot colours are completely black plates, by removing the black background you can paint back in specific spots of colour using the paint brush tool
You can also use the 'Quick Selection Tool' to select parts of the image on the greyscale later, then you can choose the spot colour layer to add colour to the selected sections.
Similar methods can be utilised to add spot varnishes to a print job.