Multiply those results by 255 to once again get the 8-bit value, and resulting colour values should therefore be 141/38/52. Let’s do one more example of multiply with all three channels involved. CMYK documents won’t be covered here because of these additional complexities.īecause a colour value of 255 equals 1 in the equation, and a value of zero equals 0 (of course), 255 will have no effect on the colour beneath ( x × 1), and 0 will result in black ( x × 0) if we ignore any other channel interactions.
The result is 0.25, but since we’re dealing with additive colour, this means more ink achieves a darker result: a value of 75% (zero would be 100% yellow).
Say we have two squares in a CMYK document that are both 50% yellow, which gives us a sum of 0.5 × 0.5. Ink values in a CMYK document don’t work on a digital scale of fixed levels, but an analogue one of ink saturation percentages. This works differently in CMYK, we should note, because of the differences between additive and subtractive colour. Therefore, the sum involved is 0.488 × 0.488, which gives us ~0.238, or a green value of about 61 between zero and 255, darker than the original colour, of course. So what’s going on at the overlap? First up, that 125 green value needs to be converted to a value between zero and 1. Naturally, the top square is set to Multiply. They have colour values of 0/125/0 − only the green channel has a value, to make this as simple as possible. Multiply is the simplest mode to demonstrate as it has the simplest equation: x = a × b, in which x is the resulting colour value, a is the top or active layer, and b the background. With all this talk of examples, we’d better have an actual one.
Again with Multiply as an example, the top colour is multiplied by the bottom colour. The resulting colour is the combination of all three. So, in Multiply, for example, Red is multiplied by Red, Green by Green, and Blue by Blue. In the basic lightening and darkening blends at least, colours are compared channel by channel. For example, if a colour has a green value of 200, this becomes 0.78125 (200 ÷ 255). When doing the maths for blending modes, Illustrator converts this into a value between zero and 1. You’re probably aware that in RGB colour, each 8-bit channel contains a colour value between 0-255. Wherever possible I’ve verified the results with experimentation, but if you spot any errors I will gladly correct them.īlending modes are equations between two or more colour values that sit on top of one another in the stack order. I compiled this using the following sources: I’m going to use the modes in Illustrator as examples there are more modes in Photoshop, but the same principles apply to both. But how? Here I’m going to attempt to explain what they’re doing behind the scenes, and hopefully gain a better understanding myself in the process. Multiply darkens things, Screen produces highlights, et cetera. If you’re anything like me, you probably know what a few of the blend modes do intuitively, but have no idea what they’re actually doing to the colours you use.
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