Luminosity Masks

Clive R. Haynes FRPS

Before we begin to explore the possibilities offered by Luminosity Masks it's a good idea to understand how masks work.   An awareness of the underlying principles of masks in Photoshop will help to better understand why Luminosity Masks are more effective for some pictures rather than others.  Choosing when to use them is key.

Briefly, the effectiveness of masks in Photoshop relies upon its greyscale tonal value.  Areas of white on the mask will reveal the visibility of the layer 100%, either as pixels (if it's an image) or appearance (if it's an Adjustment Layer).  Total black upon the mask will make the layer invisible.  Where the mask is of shades of grey the visibility pixels or effectiveness of an adjustment will be revealed or hidden depending upon the density of tone.

The image below shows the effect of a stepped gradient mask where the amounts of white through grey tones to black are obvious.  The more gentle the transition the more subtle the changes.  The second illustration shows a gentle gradient from white to black.  Remember, 'white reveals', 'black conceals'.

The scene is the 'Vital Spark' moored at Inveraray, Loch Fyne, Scotland.  I applied an Adjustment Layer using Levels, setting this to be high contrast.

Below is a10 step mask I made.  Where it's black (extreme left) the effect of high contrast is concealed.  Where it's white (extreme right) the effect of high contrast is revealed.  Along the way, shades of grey gradually reveal the visibility of high contrast.

When a gradual gradient mask is applied the transitions are invisible. See below

Smooth Gradient Mask Applied
Smooth Gradient Mask


With this principle in mind it's easy to appreciate that if we can reveal the various areas of tone within an image and express them as white, black or shades of grey, we should be able to use this base to selectively control aspects of the image. 


Luminosity Masks continued.....

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