But one thing at a time-
Here's a quick example on Curves and Masks-
This shot of Teresa on a park bench- represents a typical family shot on a sunny day. The subject on the bench does not have a direct light source and the background is actually lighter and colorful. The eye will be drawn to areas of high contrast and/or the lightest area in the image. We want to emphasize the subject by diminishing the light and contrast of the surroundings.
We will take this image-

And end up with this image-

Perhaps more correction than you would make in real life but we need to make the difference obvious. I will assume you can copy the first, pre-edit picture to your desktop and load it into Photoshop. If you can't let me know.
A note about menu commands- There are often four ways to bring up an action or command in Photoshop- the pull-down menus from the top menu bar, icons within a layer, right-clicking layers, and keyboard shortcuts. I use keyboard shortcuts and right-clicking most of the time.
By the way- if this was one of your own pictures you should make sure to save a copy that says "original" in the title. Always work on a copy until you are really, absolutely sure you don't need the original version again. When you have the picture for this lesson ready to work with select the layer, right click in the blue area (layers are blue when you select them) and select "Duplicate Layer". You have to "ok" making a Background Copy in a window that pops up. Command-J in Mac will duplicate the layer, try Control-J Windows (?).
Once you have the duplicate layer, click on the duplicate layer to make sure it's the current selection. Then hit Command-M for Curves or from the top menu bar Image > Adjustments > Curves. Your screen should look like this-

The gray curve in the box is the histogram, the distribution curve of light values in the pixels from darkest (left side) to lightest (right side). With your cursor grab (left-click) the diagonal line in the center and drag the line straight down to the 25% point- halfway between the middle and bottom-

Look at the right side of the curve, the line is very "steep" now. A steep curve increases the contrast. Also, when your image is in RGB mode, the color is more saturated. So, even though we've made the background darker, we haven't made it less interesting to the eye because we increased the contrast. Now grab the top-right corner of the curve line and drag it straight down 25% along the right edge. It should look like this-

Notice how the bright areas became dull? We flattened out the pixel curve in the brightest areas of the image. Go ahead and click the "OK" button in the Curves window. Now, using a mask, we can erase the effect of this curve we just created in specific areas. Like where Teresa is sitting!
So now look at the bottom of the Layers panel where there are some icons. Point at the one which is a gray square with a white circle in the middle. If you hold your cursor there it should say "Add Layer Mask". Click that icon and a white square will appear next to the thumbnail image in your top layer- (ignore the fact that my screenshot says "Add Vector Layer")

Now I want you to take a moment to be aware of more "selection" options. Sometimes you can take actions on your picture when you think you're working on the Mask and visa-versa. Notice that the white box in the top layer (the Mask) has an outline or partial box around it. Click once on the picture thumbnail in the top layer. Now that picture should have a partial box around it and the Mask- the white square- has a single line; it's not the selection any more. Click again on the Mask (white square) and lines will appear around it, showing that it is the active selection.
So here's the whole point of a Mask- if it's white, it is transparent. When it is white it is not doing anything at all- it is not masking or "hiding" anything. If it is black it is completely opaque, or completely hides whatever is on that layer. And any shade of gray will hide the layer based on percentage with 100% = black.
We will now select a Brush and paint Black on a portion of the Mask. On Macs you can just hit "B" to bring up the Brush tool. Otherwise click on the icon for the Brush tool on the left side tool bar. (For me it's the 8th one down the bar, a paint brush icon.) To make sure we have a Brush of decent size in the upper left portion of the menu bar click the drop-down arrow next to "Brush". Hopefully there is a basic selection of brushes already loaded. We need to use a "soft" brush- one that fades at the edges, not harsh. For this lesson I was using the 100 pixel size-

Click once on the gray border of the picture to make the Brush selection grid disappear. Before brushing we need to verify the color being used. In the lower left you will see a two-box icon. Hopefully one is black and the other white right now. We need the left one, the front one, to be Black. If it is not Black you can click in the middle of the box and a window will pop up with a color spectrum. Select Black in the bottom left corner.
Now, simply use the Brush tool and begin "painting" with your cursor over the head and torso of Teresa. You should see her immediately become lighter compared to the surroundings. And look at the mask in the top layer- this is where you are painting Black. You can see the shape you have been painting into the white square.

At this point you would save your file and be done! I always add the word "edit" to my files as I'm working towards a final copy. That's all for this "lesson"! We'll keep adding complexity and different ideas as we go!




