After the latest journal from
janaschi over a doubt on LAB, I realized more than many people need help about colour modes since they don't even know what that is and what it's for. Therefore, I found myself in need to write this basic "tutorial" on this theme. Hope it helps.
I'll be adding more colour modes to this same journal in the future._________________________________
You can choose colour modes in Photoshop by clicking Image > Mode.
RGB and CMYK are the most standard colour modes, but it all depends on what you look for.
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RGB - Red Green Blue. It represents all the primary LIGHT colours. It's a mode used for screen images, since it shows the colours bright and vivid. It's a good mode for when you just want to have a digital picture, displayed in digital ways. If you only need your picture for the internet, for a wallpaper or just to be stored on your computer, you can choose this mode.
CMYK - Cyan Magenta Yellow K (Black. It uses the letter K instead of B since B is for Blue). It represents all the primary INK colours. It's a mode used for printing images, since it shows the actual look of the colours when they are printed on paper (i.e. not so bright). It's a good mode for when you want to print an image, since the colours used for the printing are ink, using the 3 primary colours + black.
Grayscale - as it says, it's a colour mode that ranges from black to white, including all gray tones in between. It's a mode used for all b/w pictures that have no other colour, since it takes all colour information. It's a good mode for when you scan a line-art or want a b/w picture that on screen looks blueish or yellowish, since it takes that away in order to have only pure gray, black and white tones. It is also recommended for pages that contain only text (with no colour). Additionally, the picture is lighter/consumes less space on your computer, because it was free from unnecessary information.
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You can convert an image to any colour mode on Photoshop, any time you have a different destination for it. However, it is recommended that you originally create or scan the picture to the right colour mode (which depends on what you need the image for), or to a colour mode that allows you to have a good quality image in several ways.
LAB mode is an example, since it allows a good colour viewing both on screen and on paper. This will be the next featured colour mode.