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Masking 1/3: Layer mask

or; how to cut out stuff; part one.

This tutorial (in three parts) will show three different masking options in Photoshop - starting with the easiest. If you already are comfortable with one method, you can jump to the one you need:

  1. Layer mask (this)
  2. Vector mask
  3. Clipping mask

The file I will use in this tutorial can be found HERE - if you want to use it.

General tips:

Layer mask

  1. Bring your image into Photoshop (file -> open).
    In your layers palette it should only show a layer named Background
  2. Right-click (ctrl-click if you only have one button on a mac) and choose "Duplicate layer...".
  3. You now have two layers. Hide the background layer. This is just so that if you damage the image you can still bring the original background layer back.
  4. Now, click the "create new fill or adjustment layer"-button in your layers palette and choose "Solid Color..." This will create a layer with a single colour. We will use this as our background while masking.
  5. Choose a colour that differs from the subject in our image. I picked a green.
    Note: You can change the colour at any point by double-clicking the coloured icon on the layer.
  6. You now have a new color fill layer (with a white mask). If it is on top and covers your image, drag it down under the "Background copy" layer.
  7. Now that we have a background (the green) we can start masking our image. First, click the "Add layer mask" button in your layers palette. This will create a new white mask in our image.
  8. A layer mask (similar to a "matte") is actually a black and white image, where the brightness of the pixel determines the opacity of the layer.
    What does that mean? Well, it means if you paint with black in the mask it will hide parts of the layer, and if you paint with white it will reveal it. Let's try.
  9. Select the brush tool
  10. Reset the colours to black & white
  11. Choose a hard brush, and a brush size of e.g. 40 px.
  12. Draw a line to see that everything is ok. A green line appears, and if we look in the layers palette we see that it's because we have a black line on our mask, making that area transparent (hidden).
    - If you do not get this result, undo (step back in history palette), and make sure you have the layer mask selected by clicking it.
  13. Now, press 'x' to switch the foreground/background colours - so you get white. Draw on top of your line. As you can see white makes the layer visible again. That's all you need.
  14. Now, zoom in to 200 % by using "ctrl +" on a pc, or "apple +" on a mac.
  15. Now, start masking by painting with black and white.
    - Press 'x' to quickly switch between black/white (hide/show).
    - Hold down space and click-drag to pan around.
    - Change brush size with [ and ] or by right-clicking (40 is too big).
    - Go around the edges with a small brush, then use a big one to clean up the rest.
    Remember that you do not need to make perfect brush strokes, if one is a bit wrong, just press x and clean up the mistake.
  16. When you feel happy, zoom back out (ctrl -, or apple -) to 100% and have a look.
    If you did it right you should have something like this (I have zoomed out to 25%).
    Look at the layers palette and make note of the black and white mask. :)
  17. Your layer is now properly masked. Good job.
  18. To put it on a different background you can drag the layer into other open documents, or paste/drag/place a background picture into your document and place it below your masked layer.
  19. When saving, make sure you save as "Photoshop document (.psd)" to keep the layers intact. If you need to show the finished image to someone, save a small copy as JPG or PNG, but keep the original.

My final .PSD file can be found HERE (9 MB) if you want to have a closer look.