How to Control Layer Masks in GIMP

Tuesday, July 5, 2011  at 6:58 AM
Learn what Layer Masks are and how to control them in GIMP.  You can also call this: Photo-editing like a ninja with GIMP--make everything do what you want!

The cool thing about using Layer Masks is that you can control what effect you see in different parts of the picture.  Want one area lightened without washing out a patch right next to it?  You can do it.  Want to increase saturation for one object but for nothing else?  You can do it.  Want to highlight a few areas without looking like you cut and pasted them on top of the background?  YOU CAN DO IT.  Obviously, I'm pretty excited about Layer Masks.  This tutorial follows naturally from the one before, How to Create Stunning Landscape Photos in GIMP, which was basically Introduction to Multi-Raw Processing and Layer Masks, only with a less-scary sounding name (I know, I'm so sneaky).

Welcome to the thirteenth article in my Photography Editing in GIMP series!

Previous articles:


Article 1: Easy Photography Editing in GIMP
Article 2: How to Crop in GIMP
Article 3:  How to Control Saturation in GIMP
Article 4: How to Control Contrast and Lightness
Article 5: How to Change Color Photos into Black and White
Article 6: How to Level a Horizon
Article 7: How to Correct a Skewed Perspective in GIMP
Article 8: How to Square All of Your Corners in GIMP
Article 9: How to Adjust Curves in GIMP
Article 10: How to Adjust Color-Specific Saturation in GIMP
Article 11: How to Blur a Background in GIMP
Article 12: How to Create Stunning Landscape Photos in GIMP

These tutorials use the free photo-editing program GIMP.  I am not being paid to endorse GIMP--I just really like it!

This tutorial will show you how to take your photos from this:

Chris and me in Eastern Europe by Danalynn C

to this:

Chris and me in Eastern Europe by Danalynn C

There is another before/after example at the end of this article.

Notice that I cannot use the method in the previous article, where I have a Layer Mask with a gradient from transparent to opaque, because most of the buildings are behind Chris and me.  If I adjust the contrast, saturation and curves for the buildings, Chris and I will be too saturated, and the reverse is true as well.  This is why this method of using Layer Masks (like a ninja!) must be used to edit this photo.

Step 1: Open the photo in GIMP and make sure the Layers, Dialogues, Paths Dialogue Box is open.  Right click on the layer in the Dialogue Box (it will be named Background) and select Duplicate Layer.

Chris and me in Eastern Europe by Danalynn C

Step 2: Right click on the new layer, click on Edit Layer Attributes, and rename it something descriptive.  I named mine People, so I would know what I would be focusing on editing for that layer.

Chris and me in Eastern Europe by Danalynn C

Step 3: Click on the eye symbol for the People layer in the Layer Dialogue Box, so you do not see it.  You only want to see the Background layer at this point.

Chris and me in Eastern Europe by Danalynn C

Step 4: Edit so the background looks fantastic!  I increased saturation, especially red and blue saturation, then adjusted curves.  Pay no attention to how terrible this is making the subject of your next layer(s) look--here, the saturation has made the coloring of the faces completely wonky, but it doesn't matter.

Chris and me in Eastern Europe by Danalynn C

Step 5: After you are happy with how the background looks, select the other layer.  You want to make sure that the eye symbol for the People layer is turned on, and the eye symbol for the Background layer is turned off.

Chris and me in Eastern Europe by Danalynn C

Step 6: Edit this layer for the people (or whatever you want to focus this editing on), paying no attention to what your edits do to the background.

Chris and me in Eastern Europe by Danalynn C

Step 7: After all of your edits are done to this layer, click on the People layer in the Layers Dialogue Box and select Add Layer Mask.

Chris and me in Eastern Europe by Danalynn C

Step 8: When the menu box pops up, select Black (full transparency) and click OK.

Chris and me in Eastern Europe by Danalynn C

Step 9: At this point, the transparent Layer Mask is now attached to our People layer.  This means that currently our entire People layer is transparent (as specified by the Layer Mask).  Every pixel in the Layer Mask corresponds to the same location pixel in the layer, and the layer mask pixel tells the layer pixel how it will behave.  If the Layer Mask is black in an area, that means that the corresponding area of the layer will be transparent and we will see 'through' it to the background layer.  If the Layer Mask is white in an area, that means that the corresponding area of the layer will be opaque, and therefore that we will see it.

Right now, we are going to 'paint in' the opaque areas of our layer mask.  First, in the Toolbox, select the paintbrush (I like to use a 'fuzzy' paintbrush so my opaque edges aren't so obvious).  Select the proper scale (size) and to start, put the opacity at 20%.  Sometimes I will increase opacity to 40% if I have a very defined area that I am 'painting,' sometimes I will decrease opacity to 10% if I want a very subtle effect.

Chris and me in Eastern Europe by Danalynn C

Step 10: Because we want to paint in the opacity, we want to paint in white (remember, white means opaque) and not in black.  Therefore, click the little arrow to switch the black and white colors in the Toolbox.  White should now be on top and black should be the bottom square.

Chris and me in Eastern Europe by Danalynn C

Step 11: Make sure that the layer mask is selected in the Layer Dialogue Box (a white box will surround the image of the black layer mask).  Paint where you want the top layer to show up!  For me, since my top layer was People, I painted where the people were.  As I painted, I could see the 'proper' coloring from the top People layer slowing showing up, layering on top of the Background layer.

Chris and me in Eastern Europe by Danalynn C

Step 12: If you click off the eye symbol for the background then you will be able to see exactly what you are painting.  Sometimes I like to paint the opacity while looking directly at the layer mask because then I can see if an area is patchy, if my opacity is strong enough (or too strong), and what exactly is showing through.

Chris and me in Eastern Europe by Danalynn C

Step 13: Once you are happy with this effect, you can either flatten the image and save it, or do another layer with a layer mask.  I usually like to do several layers with layer masks for a stacked effect.  For example, in this image I will have one more layer with a layer mask on top.  This layer will have light highlights and saturated colors so I can bring out some bright points in the photo.  To do this, duplicate the background layer, rename the new layer (I named mine 'Lightest layer') and drag this new layer to the very top of your layer pile in the Layer Dialogue Box.

Chris and me in Eastern Europe by Danalynn C

Step 14: Turn off the eye symbols for the People and Background layers and edit the Lightest Layer so it is bright and has some nice saturated colors.

Chris and me in Eastern Europe by Danalynn C

Step 15: Right click on this layer and add a transparent layer mask.

Chris and me in Eastern Europe by Danalynn C

Step 16: Select the proper paintbrush to deal with this layer.  Generally, I will decrease my paintbrush size as well as the opacity for this highlight stage--in all of these layers you should be working from most general to most specific.  Select the Lightest Layer layer mask (it will be outlined in white) and paint in your opaque areas.  You will not be painting much in this layer mask.

Chris and me in Eastern Europe by Danalynn C

Step 17: Turn on the eye symbols for all the layers.  Do you like the overall look?  If so, flatten all of the layers under Image -> Flatten Image.

Chris and me in Eastern Europe by Danalynn C

Step 18: Save and enjoy your new edited image!

Chris and me in Eastern Europe by Danalynn C

Here is another image that I edited using this same method.

Before:

In Budapest by Danalynn C

During:

In Budapest by Danalynn C

After:

In Budapest by Danalynn C
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