Adobe Photoshop Tutorial. Copyright Michael B. Karbo.

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    More about the mask

    You have a picture in two layers with a layer mask associated with the uppermost layer. Let us look a little closer at this setup.

    1.   Start by selecting a larger thumbnail for the layers. Then it is easier to see their content. Click on the small round button in the upper right in the Layers palette:


    2.   Choose menu item Palette Options … and then the largest thumbnail size:

    3.   Now you can clearly see the layer content. See the layer calme:

    4.   Notice that the original picture is unchanged. There is no ”hole” in it, nor has anything else happened to it. That is because you have worked on the mask that is seen to the right. Let us look a little closer on that. Try to hold the Alt key down and click one the mask icon:

    5.   Then you only see the mask in the large picture. By us it looks as you se in Figure 43.

    6.   Click again with the Alt key to see the whole picture.

    Figure 43. The mask, wich helps forming the picture in Figure 42.

    The mask is a channel

    The mask in Figure 43 is thus associated with one of the picture’s layers, that is ”calme”. The mask itself is physically a channel in the picture.

    Photoshop has up to 24 channels associated with each picture. The individual channel is actually an eight bit gray tone picture; in our case the mask is seen as a gray tone picture. It is black in the center surrounded by white. In the transition between the two areas there are various gray tones. The gray tones in a layer mask gives various degrees of transparency.

    The advantage of the mask is that it principally works independently of the actual picture. It does not change anything in the picture’s pixels.

    If you right click on the mask’s thumbnail in the Layer palette, you get a number of options that you can try for yourself. Remember that you can cancel the last previous operation with Control+z.

    Figure 44. Options by right clicking on the layer mask.

    Disable Layer Mask means that the mask is de-activated. Then the picture (in this case the uppermost layer) is totally unchanged.

    Discard Layer Mask means that the layer mask is deleted – it is removed and the original picture is unchanged.

    Apply Layer Mask means that the mask ”melts together” with the picture. So there will be a ”hole” in the picture’s data, and the mask (the channel) is removed from the layer. You should only do that if you are 100% finished editing the mask, and you know what it will be used for.

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