Layer Masks for fun and profit! - DPChallenge Forums

Tamron SP AF 17-50mm f/2.8 Di II LD Aspherical (IF) for Canon

02/22/2006 03:11:14 PM · #1

Layer masks are important tools for non-destructive image editing.
They can be used to make incredible fine detailed adjustments where formerly you would have used the eraser or the history brush tools. Those are destructive tools and once saved there is no later recoverability.

Layer masks are used for background replacements, undoing an adjustment layer change, blending pictures and other fun stuff.

An example:

Lets suppose we have a picture like this one that has a rose on one layer and a face on another. Lets further suppose we want to change the blending of the rose on the face but we want to do it in a non-destructive way so that we can later bring back parts of the rose if we change our mind tomorrow. Layer masks let you be indecisive forever!!

Here are the boring things you gotta know about layer masks:

Layer mask fundamentals
1-Each layer can have a mask attached to it.
2-A mask determines the transparency of information from that layer to the rest of the image.
3-Mask tranparency is determined by the amount of black, white and grey on the mask itself.
4-Black is used to block out things from a layer. Black is complete transparency. This means it "blocks" or covers up what is in that place in that layer so it will not show up on the image at all but everything "below" it shows through. It does not erase anything.
5-White is used to let things show up from that layer in the image. White is complete opacity. White completely "covers up" whatever is BELOW that layer so it can't be seen in the image.
6-Grey is used for partial transparency. That is, where there is grey then part of the contents of the layer will show up in the combined image and part of what is below shows through.

There are a variety of tools that can be used to create black, white and grey on a mask. In this example the paint brush would be the one used.

The fun part of masks!
Painting a little black to block or a little white to show things up on different areas of the layer to make subtle image changes is the creative, artistic and fun part of layer masks!!

The confusing part of masks!
It sounds strange to think that black makes things transparent and that white makes them opaque and you would be right... it is strange! But you have to think in terms of the layer itself and its relationship to the other layers of an image to understand it better.

For the layer alone it makes sense that painting black blocks out things on that layer. That idea originated with masking from way back in the old days of "wet" darkrooms when you made a cardboard cutout that you waved under the enlarger to block light when exposing the print paper. Using black in the digital darkroom mimics that process for one layer.

What is different about the digital darkroom is when black is used to block out things in one layer it then translates into transparency for the rest of the image below it. That is why you will read that black means complete transparency. Strange, but true!

Furthermore, it is VERY important to know if you are in the mask part of the layer or in the data part of the layer. It can be confusing and cause trouble when you paint. If you paint a big white or black brushstroke across the screen when you expected to hide or show something using the mask part it simply means you are in the data part of the layer. Undo that immediately and return to the mask layer and continue. It is guaranteed you will do that a lot! :)

Down to business!
Now you are probably saying to yourself, "Self; I got it, you can add a layer mask to a layer and you can paint with black, white and/or grey on the mask to hide or show things... so how do I ACTUALLY do it?!"

Assuming the rose layer is above the face layer in the example, here is what you do to work with the rose...

Using layer masks in Photoshop
1-Select "Window->Layers" and click the "Layers" tab to bring up the layers dialog.
2-Drag the tiny rose picture to the "add layer mask" icon that looks like a little camera on the bottom of the pallet. Now a white box shows up to the right of the rose image box on its layer. White, of course, means it is opaque to everything below that layer.
3-Click once on the mask box and return to the image. That is critical, otherwise you will paint on the actual layer data. As you can see the rose now covers the face just like it is supposed to with a completely white layer mask.
4-Be sure the default black/white foreground and background colors are selected.
5-Select an appropriately feathered brush size and opacity and with the foreground black color simply paint away the parts of the rose you don't want visible in the picture. Make a mistake and switch the foreground color to white and paint with white to bring it back. Neat, huh? Change the opacity of the brush to paint with grey to blend the images together just the way you want. Now you are an artist!

It is THAT simple! :)

Message edited by author 2006-02-22 16:53:39.

Phil

Canon EOS-7D

02/22/2006 03:17:22 PM · #2

Thanks much for doing this Steve. I'm a Photoshop moron and I appreciate it when people post these tutorials.

Canon EF-S 18-55mm f/3.5-5.6

02/22/2006 03:21:03 PM · #3

Originally posted by dudephil:

Thanks much for doing this Steve. I'm a Photoshop moron and I appreciate it when people post these tutorials.

Today's Photoshop moron is tomorrow's guru!

Kivet

Canon EOS-400D Rebel XTi

02/22/2006 03:29:37 PM · #4

or Todays Gimp moron ...I meant Guru :)

Panasonic DMW-LTZ10 1.5x Teleconverter

02/22/2006 08:09:46 PM · #5

If I do say so myself, this is a pretty good description how layer masks work and how to use them. So thought I'd bring it to the top of the list again so you all would have a chance to see it. :)

* Steve pats self on back for contribution of useful information to combat the usual whining and complaining ;) *

KiwiShotz

Panasonic DMC-FZ20

02/22/2006 09:00:01 PM · #6

Originally posted by stdavidson:

* Steve pats self on back for contribution of useful information to combat the usual whining and complaining ;) *

So Brett whines that he hasn't done it for Paintshop Pro, asks why not and throws in a pout for good measure.

just kidding ...

Brett