OC Methods for masking (cutting out) objects

(Moving over one of my reddit comments)

A user was struggling with masking this image.

Comparison of selection methods (on this image, but the methods work for other images as well)

There are many ways to select/mask things, and no single tool is great in all situations. Often you combine multiple tools/techniques to make a single selection/mask. So worth learning multiple tools.

Note: You want to create a mask (layer mask/vector mask). Don't delete/erase.

Automatic methods

The "automatic" tool, like Quick Select, Magic Wand, and Object Select, are great and super fast - but require good edge contrast for useful results. So in this case, the right side of the hand they can handle, but the left side, and fine details like the stems, fails miserably:

These tools can often serve as a great starting point that quickly gets you 90% of the way there, and then you use manual tools for cleanup. In this specific case however, they won't help much.

Manual methods

A manual method requires you to define the edge yourself. Edge contrast doesn't matter, you decide where you want the edge. The quality/accuracy is entirely up to you.

The main manual methods are as follows:

The Pen Tool was done the most accurately/Detailed. By making it less accurate, time can be saved (to be fair, this goes for all methods).

The lasso is problematic as it can only do straight lines, and accidental double-clicks can close the selection early (causing a bit of cleanup). Doing it in sections (adding/subtracting) can help. I wouldn't recommend on this image, but it is an ok substitute for the Pen Tool for beginners (who have not yet learned the pen tool).

The masks of the Pen Tool and Lasso Tool both have their masks set to 0,5px feather to better match the softness of the image. (Note: using the slider, not destructively).

Remember: You can combine all methods. Maybe you want to use the Pen Tool for the hand, but manually paint the flower? Great! Do that.

Defringing

You might noteice that every single masked image has a bit of a "halo" around the edges. Dark where the background was dark, and bright where the background was bright.

This will happen even with a sharp and theoretical perfect mask made by the gods themselves. A pixel right on the edge of an object will contain a mix of foreground and background. Let's say 50% of each. So a 100% white subject on a 100% black background would have gray pixels on the edges.

For a pixel that is 50% foreground/background, a perfect mask should make it 50% transparent. The problem is that the pixel still has a color that contains some of the original background color, so when placed over a new background you get a mix that is 25% subject color, 25% original background color, 50% new background color. Yuck.

It is especially visible/problematic on thin and soft edges, and when the new background color is very different from the old.

The "quick fix" that can help in many situations is to simply contract the mask a bit. Essentially just cutting away the edge. This creates a smaller mask, and might be fine in many situations, but with fine details like hair, or this flower, it's not such a good idea.

The next option is to "simply" recolor those edge pixels. Multiple ways of doing it, but I would recommend doing it on a new layer clipped to the masked layer if possible. Basic methods:

  • Brush Tool: Simply sample colors near the edge and paint over the bad edges manually.
  • Clone Stamp Tool: Clone from near the edge to replace the edge pixels.
  • Masked adjustment layers: Use adjustment(s) to correct the color, and a mask to limit it to the edges.
  • "Decontaminate" option in Select and Mask: It replaces the color of semi-transparent areas with the color of the nearest opaque pixel. Works best for sharp edges. Often a great starting point, then manually fixing the bits where it did a poor job. That's what I'd usually do.

I wanted to show a screenshot of the last option, but for some reason it is bugged for me in the current version of Ps. So here is a screenshot of what it would look like if just using the brush tool:

Manually going around the entire edge like this can be time-consuming (about as much time as masking it with the brush tool), so I would recommend placing it on the new desired background first if possible to see where it is actually needed (then only fix those bits)!

---

With all methods, it is a bit down to personal preference, and how much time you want to spend vs. the quality you desire.

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