A lot of people are confused with masking and they prefer to stay with the eraser tool. Eraser works great but when it comes to non-destructive editing, masking does a better job. It might be confusing at first but once you know the basics, it could be a life saver tool. First we need to understand the difference between destructive and non-destructive editing.
Keeping an option to go back to your original file at any point of your editing process is non-destructive editing. With non-destructive editing you do not make any permanent changes on your original file but add the effects on top of it with an option to go back incase you are not satisfied with your result. Where as destructive editing is where you make all the changes in your original file. Now you have a new file with the change applied and you can’t go back incase you want to alter the effects. Non-destructive editing is more of a professional way of editing photos where the option is always open. When you need to remove something or erase in a non-destructive way it’s the masking that does the perfect job.
Now let us understand what masking does. With masking you need to understand the role of two colors. Black hides the content where as white reveals the content.
In the figure below, I want to get rid of the chair my subject has knelt down on; to make it look like it’s levitating. These are the two shot I took on my tripod. One with clean background other with the chair and the subject. I will try to do this with both eraser and masking tool. Lets start with the mask tool.
Step 1. Add a white mask on top layer. You will not see any change on this step.
Step 2. Convert the white mask into black with Command+I in Mac and Ctrl+I in Windows. With the change in mask color into black the layers gets hidden.
Now as shown in the figure, as the color of the mask changes to black, the content gets hidden.
These two-steps should make you clear about white revealing and black hiding the layer.
Step 3. Repeat step 2 to get the mask back into white again.
Step 4. Brush over the mask with black as a foreground color. The area you brush will get hidden
Step 5. If I brush over the same area with white color, the layer will start to appear because we know white reveals.
We can brush with this color as many times as we want unless we get the desired result.
Now lets try with the eraser.
Step 1. Select eraser tool with E
Step 2. Rub the eraser over the part you want to erase it
Eraser does the job too but I can’t get the erased part back expect for using undo tool or history tool, which are limited to certain numbers. Now that becomes my new file. This is destructive editing.
So for erasing something, masking does a better and efficient job than eraser . Below is the final Image.