An image brought into Photoshop will always appear in the layers palette as “Background”. Consider this to be the original base layer from which all other layers will be added on top of it. Now create an adjustments layer. And for our purposes today, we'll choose brightness/contrast. To do this, go to the adjustment layers menu and open brightness/contrast. A new layer appears.

Whenever an adjustment layer is created, it comes with a mask. The white rectangular icon to the right of the layer icon is the mask as you see below. The mask is a reversible way to hide all or part of the layer. To demonstrate this, let’s first make a brightness/contrast adjustment on the layer by using the properties slider tools, make it a dramatic change, as you see below. I opted to reduce the brightness and increase contrast.

Notice the adjustments apply to the entire image. Now click on the mask to highlight it (white border line around it). With the mask highlighted, the mask properties appear above the layers palette. At the bottom of the palette is a small box titled ‘Invert’. Click on it and notice what happened to the layer mask. It turned black. Also note how your image reverted back to its pre-edited version, as you see below. You can uncheck the ‘Invert’ box again to bring it back to white and see your edits again.

To understand what just happened, you must understand the following - white reveals, black conceals. The default layer mask that appears with a new adjustment layer is all white, meaning all adjustments made to that layer will be revealed through the entire image. When it is inverted, it becomes black, which conceals all the edits from the image.

So why would you want to conceal your edits? There really is no reason to conceal them all; but what if you could conceal some of the image and reveal only the a portion you wish to apply brightness/contrast?  This is where layer masks become amazingly useful in making selective edits. You can selectively reveal and conceal by using the brush tool. To begin, invert the layer mask again (make sure it is highlighted first), so it is completely black. Next, click on the brush tool and make sure on the top horizontal panel the opacity is at 100%. Also, you want the brush hardness to be 0%. Click on the arrow next to small circle icon to see a drop down menu where you can adjust the brush hardness. Drag it all the way to 0%. 

Toward the bottom of your vertical toolbar, make sure the foreground/background boxes look like the following image (white on top, black on bottom). With white on top, the brush tool will become a revealing tool.

Now take the brush (adjust its size accordingly with the left or right bracket key) and brush over the areas of the image you would like to apply your brightness/contrast edits. The brush tool is being used to reveal a portion of the adjustment layer. You can see the change in the layer mask icon, but here is a tip to help you see it better; hold down ‘alt’ ('option' for a Mac) and click on the layer mask. Your image becomes the mask. Repeat that to bring back the image.

You can reverse your edit by either undoing your last edit, or you can go back to the foreground/background boxes and switch them by clicking on the little arrows above them. Now black is on top which makes your brush a concealer. Brush over the revealed areas again to conceal all or some of them, like seen below.

One more thing you can do to help you with the conceal/reveal brush strokes. Click on the brush tool and note the opacity window at the top. You can change that from 100% all the way to 0%. By reducing the opacity, you reduce the effect of the brush, meaning it will reveal or conceal partially. Partial reveal or conceal will appear in the mask as gray. The darker the gray, the more concealed; the lighter the gray, the more revealed. This gives you more control over your edits. Below, I made a few more reveal and conceal brush strokes using 50% opacity or less until I achieved the effect you see below.

Now you can begin to see the powers of the layer mask for selective editing; however, applying the brush tool is only the tip of the iceberg. And it is a very big iceberg! The method I showed you here is relatively crude, but it is a start. There are many ways to refine the selectivity of conceal and reveal, but I will leave it at that for now. Stayed tuned for my next blog where I show you an easy but effective tool for selective masking.

Thanks for looking on and if you want to learn more about Photoshop layers and masks in Photoshop, need help with your editing workflow or simply want to get started in Photoshop, I offer tutorials at $75/hour. Please check out my website and feel free to contact me at bigcypress214@yahoo.com.