Saturation masks is an easy way to extract complex objects in Photoshop

There are plenty of functions for masking in Photoshop, and each of them is useful in its own way. Whether it’s color selection, focus masks, the new ~~and kinda annoying~~ mask-and-select dialogue or my beloved channel selection.

If you are following our blog, you should be familiar with my love for channels. Channel selection is always based on the contrast between red, green and blue, and I am manipulating them after duplicating the channel with the highest contrast.

Another way to create masks is using selections based on saturation. THis is not a well-known method, but it’s a very powerful way to create awesome masks when dealing with complex selections.

Why do we need Saturation masks?

If you work in a studio, you might be able to shoot against a white backdrop. An important property of white is it’s 0% saturation, so everything “human” you put in front of your seamless white will have more saturation as your white background. You can utilize this to create a fast and precise mask.

The final result

I decided to use an image of our Ophelia Overdose stock package. (To be honest, this is quite useless as the images in the Ophelia Overdose package already have a mask, but I thought that I can recreate them as an exercise and show you how good those masks are).

The background here is not 100% white and the costume is not easy to mask out. Most of the automated tools are doing a horrible job here. (you can see the saturation selection proce ss at the top of the post)

Let’s see the masked out image in front of a green background. The process took a bit over 3 minutes and it’s not 100% perfect. As I said – you might combine this technique with other masking tools.

A Step by Step Tutorial

First, let’s see where the problems are in this particular image:

there are areas with less contrast between model and background
some areas are semi-transparent
in this area the costume is white – so there is no saturation
the background is not pure white

Let’s solve these problems

I’ll address the first issue, by duplicating the background layer (I did it twice to get even more contrast) and putting it in the “multiply” blending mode.

Now I am going to neutralize the background (Problem number 4). A curves layer does the trick: click on the middle eye dropper tool and click on a gray area near the model. The background is now neutral gray.

Create a curves adjustment layer
Click on the middle eyedropper tool
Pick an area near the model

The background is now completely gray and I am creating a temporary stamp. Control+Alt+Shift+E does the trick. Everything’s now on a new layer. Let’s generate the saturation channel now.
Filter-> other filters -> HSB/HSL

The next dialog will ask me for an input mode and the row order. Let’s pick RGB as input and HSB as Row order.

What happened here? Our image is made of three channels – red, green and blue, the primary colors. These channels are used as input and the row order – or output of that filter – converts it to HSB.
HSB stands for Hue-Saturation-Brightness, so the green channel will contain the saturation information.

The image looks like this now:

Alright, this is not really helpful, so let’s have a look at the channels. Here we are – that’s the green channel:

The neutral background turned black (no saturation) and the more saturated areas are brighter.

I duplicate the channel by doing a right click on that channel-> duplicate channel and work with a white brush with 0% hardness, 100% opacity, 10% flow and the mode “vivid light”. The size of the brush depends on the area I am working.

When painting with a white brush in “vivid light”, the effect is pretty awesome. Parts that are brighter than neutral gray are more affected then darker parts. When switching to a black brush, everything that’s darker than neutral gray will be affected.

It’s a cool process to adjust channels that way, but you’ll need to get used to it.

2 minutes later, my channel looks like this:

Now I do a Control-Click on the layer image to create a selection.

Now I switch back to my layers and delete all the temporary layers.

With the Background layer selected, a click on the masking icon creates a mask based on my selection.

That’s it! done in about 3 minutes.

Of course, this is not a “use it for everything” technique (these are rare like fairy dust), and also the created mask will not work with every background (see fairy comment), but it’s a great base and you can (as you can with any other method) further adjust it, mix it or paint on the mask in vivid light…

[via raw.exchange]