advanced photoshop

Feature preview: Top 20 compositing secrets

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Magazine previews, by Adam Smith

Professonal image editors reveal their best production techniques.

Feature preview: Top 20 compositing secrets

Here are a few tips from  issue 98’s main feature.

Create a Calculations hair mask

The Calculations option is a hidden gem, unknown to many Photoshop users, that helps to remove models more easily from backgrounds for composite images. This can be found in the Image options and effectively combines two channels into a new Alpha channel.

Once inside the Calculations dialog box there are some familiar settings you should activate. You’ll discover there are two sources. In nearly all cases set the first Source 1 Channel to Red and the Source 2 Channel to Blue. Inverting the Blue channel will clearly define the hair from the backdrop, which is ultimately what you want.

However, applying either Add of Subtract blending modes complements this effect. In our case Add worked best. In some cases you’ll discover all the hair value, or most of it, has been selected. But it’s not always perfect, so here tweak your Offset value – we’ve set ours to -200 in this image.

Clicking OK will create your Alpha channel and you can now perfect hair selection by applying an Overlay-set soft white brush to bring out more highlights and an Overlay-set soft black brush to fill in the black background. Of course further Pen Path selection and brushwork will fill in the rest of your model.

Feature preview: Top 20 compositing secrets

RAW Smart Object

One of the major factors in professional creative compositing is making the most of a shoot in a controlled environment. However, this doesn’t mean making sure that every light value is matched over multiple shots, which is actually nearly impossible when capturing outdoor and model stock separately.

Thankfully digital software always finds a way to compensate your light-matching issues, which is great and cost-effective for those of us who just don’t have the time or equipment to control an entire setting on a shoot.

RAW, working with Photoshop Smart Objects, is particularly advantageous. When shooting a model against a neutral background you can then open your photo in RAW, using native options to achieve a greater exposure – creating contrast between model and backdrop. Then simply hold the Shift key, selecting Open Object.

You’ll be in Photoshop, with your photo as a Smart Object. Proceed to make your model selection and applying masks to cut away the original backdrop. Now you can place your model into multiple settings, being able to reactivate RAW (double-clicking your Smart Object) and optimising your light control by tweaking and editing settings. This is a great building block for further effects such as painting with curves and applying colour adjustments.

Feature preview: Top 20 compositing secrets


Read more in issue 98 of Advanced Photoshop magazine, on sale now.

  • Just wondering if people are still using channels/calculations for hair masking now that refine edge has become so powerfull. And in which cases.

  • Adam

    Hi Mark. Considering that not everyone has version CS5 +, Calculations are a useful alternative.