When first learning Photoshop, most of us are introduced to the pen tool, brush tool, or maybe even the eraser tool to remove sections of a layer. However, these methods can be both time consuming and mediocre in creating a clean final image. In this tutorial I'll be walking you through the steps that I use to isolate subjects shot in studio (against plain backgrounds) for the creation of a composite image.
I want to preface this by saying that every editing method I know has at some point been inspired by another online tutorial I've come across, and adapted to fit my needs. There may be one or many other similar tutorials like this online, I in no way claim complete originality in any of my methods. This tutorial is intended for those with intermediate experience with Photoshop, as I will assume that you know which tools and adjustments I'm selecting by their names.
Step 1: Begin with an image shot against a contrasting background - for the intended purpose of a composite image I advise you shoot everything against a plain, contrasting background, like a white or black backdrop in-studio in order to gain full control of your lighting, and easily differentiate your subject from the photo. In this case, we'll be using a portrait. Once your photo is open in Photoshop, duplicate the layer before starting any work (Cmd/Ctrl+J)
Step 1a: (Optional) You'll notice that her shirt has similar tones to the background, and almost blends in. It's always best when the background has complete contrast from the image, but this isn't always possible. In this case, we'll simply brush black (carefully) over the white area in the duplicated layer. If the edges are not completely in focus, I recommend feathering your brush to match it (you can change your brush size and feather amount by right clicking anywhere in the workspace). Don't worry about overlapping other parts of the subject, as long as the edges are precise.
Step 2: Create a curves layer above the duplicated photo, and adjust the RGB tones so that the subject is the most contrasted from the background, you should have something like this.
Step 3: Create a black and white adjustment layer above curves, and adjust the sliders so that your subject is as black as possible, and your background as white as possible (or vice-versa). Merge the Layers.
Step 4: Use the burn (or dodge) tool to completely darken or lighten your subject to contrast the background further. For best results, with the burn tool use the settings: Range: Shadows, Exposure: 100%, Protect Tones: Unchecked), or the same with dodge but with highlights instead of shadows. I also prefer to feather the brush between 10% and 50%.
Brush in any remaining light/dark areas, then invert the layer (Cmd/Ctrl+I) and do the same to the background. You should now have an image with a completely white subject, and completely black background (invert it if you see the opposite) note how in the image, you can still see detail from the tips of her hair, something that you can't do well with other masking methods.
Step 5: Select all (Cmd/Ctrl+A), copy the layer (Cmd/Ctrl+C), then deselect (Cmd/Ctrl+D) (It's super easy to remember by holding Cmd, then pressing A, C, D). Create a mask on he original, untouched layer, hold Alt, and left click the mask; this will display what's within the mask (should see plain white).Press Cmd/Ctrl+V to paste your completed mask, then left click the photo in the layer to view it again. Finally, turn off visibility for your top layer by clicking the eye next to it.
Step 6: Create a contrasting, colored solid layer under the masked photo layer to view any imperfections and visible edges in your mask. Use the brush tool to make adjustments to the mask until you're happy with the result.
^Final, Cut out.
And you're done! Place the image on whichever background you wish! I recommend this process for anything with a lot of detail and fine edges, and if you're having to do this a lot it's useful to know how to create actions to automate steps like the black and white layer, merges, etc. If you don't know how to do that, I touched on it in this article (Under "Editing"). Please let me know if you found this tutorial helpful, and if you find any ways to improve the process for your own uses.