Photoshop masks for illustration- Part one: Quickmask

Using your lineart

If you’re not already familiar with it, one of the most commonly used techniques for colouring a lineart in photoshop is to put your lineart on a layer above the others and set it to multiply. This shows through the layers below it, darkening them as it does so, as if it was painted on top in transparent inks. It’s a very useful technique, and does have one advantage over this method: If you’re using a scanned, shaded image as your lineart, converting it into a selection will lose any hue and saturation it had, which is some cases might not be desirable. However, there are a number of things you can do with a black-to-transparent lineart that you can’t with a straight up multiplied one that can make this trade-off worth it.

Just like using a multiplied lineart, we can throw down things underneath our lineart and have it show through. If we’ve left it black (or indeed set it to multiply) it’ll look just the same as using a multiplied greyscale lineart.

Throwing down a basic gradient

However, it doesn’t have to be black. We can change those colours. There are plenty of ways to do that, one of which is using the hue and saturation tool.

Colourising the lineart

“But you can still do that with a multiplied lineart,” you might be thinking, and that’s true. But, you are locked into it being multiplied in that method, meaning the colour you change it to will be effected by the colours beneath it. Here, with our lineart set to ‘normal’, it will remain exactly the same shade regardless of if it is over a light colour or a dark colour.

To show you more clearly, I’ve done some loose painting under my lineart, one using a lineart set to multiply, and the other set to normal.

Lineart set to multiply

Lineart set to normal

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Obviously this looks a little odd with these colour choices, but can be very useful if for example you want to ensure your image doesn’t get darker than a certain colour, or to hide hard transitions between your areas of colour without having to use a pure black lineart (As in multiply, these will be visible through your lineart). You can even use it to work up a character with a fully transparent background by only applying colours where you want them, something impossible the usual multiply technique.

As well as this, by locking the transparency of the layer, we can use the painting tools to directly recolour our lineart however we wish.

Lock the transparency of your lineart

Use the painting tools to recolour the lineart

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With this, we can paint into the lineart, making it darker or lighter than the colours below it, something useful for bringing out highlights in an image, or softening your lineart by making it close the the colours it surrounds.

There are lots of other things you can try with this like setting your lineart to other blending modes like screen or overlay, or using layer styles to give you all sorts of different effects. Like most things in Photoshop, the best way to learn what works for you is to experiment and see what these tools can do for you.

Next lesson, we’ll be looking at the next step up from the quickmask—the even more powerful and versatile layer mask.