Photoshop's color replacement tool changes to grey (instead of white) — how can I change a grey background to pure white?

Question

I have a picture (File format: JPEG | Сolor depth: 24):

I'm using Adobe Photoshop CC (2015.5.1). I need to change background color from grey to pure white [#FFFFFF / RGB(255, 255, 255)]

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Firstly, I did it using Magic Wand Tool. I selected background area with it and then applied Paint Bucket Tool. I filled it with white color.

Selected this way:

Result after filling :

That is untidy. Some hair is cut. Background-to-hair transition bounds are sharp. It's not what I want.

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Secondly, I switched to Color Replacement Tool. Using Eyedropper Tool I selected background color and set white for replacement:

But it replaces background color to grey (not white). This "white" color is kind of transparent or extremely unsaturated. I will show it on the example of Blue color (grey changed to grey is unnoticeable).

Colors:

Result:
Instead of real blue (dark) color I get this kind of transparent, unsaturated blue.

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Question: How to change background color properly? First method is quite untidy. Second method changes colors more accurately (without hair cuttings), but colors are "transparent". How can I change background color to pure white?

Answer 1

The color replacement tool isn't working for you because its default mode is "Color", which changes hue and saturation, but not luminosity (brightness/value). That's why you get the blue or the gray→gray effect. Changing this the tool's mode to Luminosity may get you what you want. I don't have Photoshop, so I'm not the best-suited to answer that.

For an alternate way to get the result you want, Ryan's answer is great and I definitely recommend that masking approach. However, I want to show how you can get pretty good quick results with just fuzzy select and the Curves tool rather than paint bucket.

The example is in Gimp, but uses tools that you should be able to find in pretty much any program.

First, use the "magic wand" selection tool with a very broad threshold (here, about 60):

Then, Grow that selection — the goal is to cover all of the places where gray shows through the hair but not get too much of the face:

Then, use the curves tool. It's easier to see what you're doing in logarithmic view mode...

... and draw a curve like this, smashing all of the extreme almost-white highlights to pure white, and bringing up the rest very aggressively:

This leaves the corners a little bit of a bluish off-white, so repeat the fuzzy select, clicking in a corner with a much lower threshold (10, 11, something like that). Make sure "feather edges" is selected with a relatively high radius.

And then use the curves tool again, this time even more aggressively (since none of the actual subject should be affected):

This gives a result like this:

... Which isn't as good as Ryan's, but can take less than a minute and requires very little care, and is noticeably better than the Paint Bucket Fill approach.

If your final result is going to be scaled down (for web viewing, for example) I'd just use this approach. If you need the detail, create a hair mask as Ryan shows.

Answer 2

Graphic Design Stack Exchange: How to cut how hair accurately

Advanced hair extraction tutorial

First off, plugins and simpler methods are available. This is if you want to get higher quality results.

I'll be using this photo from Photo by Ariana Prestes on Unsplash.com:

Note: I'm going to be doing the body in a separate layer so I'll be ignoring it for most of this tutorial until the final few steps

Select the Channel with the most contrast in the fine outer hairs. I think Green is the best option:

I'm going to duplicate that channel and rename it to Hair Mask. This will be what I work on until otherwise stated.

Important: If your hair is light on a dark background then you need to invert some of this as far as when to Dodge/Burn and when to use Black/White.

Now to start Apply Image. Multiply or Overlay are good options, sometimes you can even Apply Image twice. Here I applied the Hair Mask to itself with the overlay and lowered the opacity in the settings a bit to not lose the really fine hairs:

I actually did Apply Image Overlay a second pass with a lower Opacity pushing the contrast a bit more. This isn't undoing the first one, its doing it a second time:

Then go into Curves (Ctrl/Cmd+M) and adjust the White and Black point sliders.

Setup some Guides so I could periodically show original vs current at 100%. Here's the first look after just doing Apply Image, Apply Image, Curves:

Now you can like ACEkin said use Brush set to Overlay. I prefer starting with Dodge and Burn though. Burn set to Shadow and I used Exposure of 12 then went over the hairs as carefully as possible. The more careful and time you take the better the results will be. This was maybe 3 minutes, not long at all:

Then at this point go ahead and switch to Brush, Black and fill in the inside. If you want you can first do Black set to Overlay and make another pass at the edges. Again, more time you take the better the results:

Alright, now use Dodge on the spaces between the hairs. Brush set to Overlay White is another option, again I prefer Dodge and Burn. I did Dodge Exposure 12 on Highlights.

Then fill the rest with White.

And let's see where we're at in the 100% view:

With your completed mask selected go back to RGB channel and then layers and apply the mask. I did the body with a separate layer as I mentioned earlier so now I've applied that as well.

Then just refine your mask using the Refine Edge command be sure to use Decontaminate Color

Now the background I picked doesn't really match the lighting and picture, but that's alright. Its not about whether the picture looks real, just about the mask. Could almost always take more time, this is by no means perfect, but here it is which is pretty good for the point of teaching the technique:

And our 100% crop this time looking at the original vs the finished:

I didn't really think about the crop area when choosing a background image to drop in. Since its hard to see that particular area, here's with absolutely no changes to my mask, just got rid of that background for a plain white background for the comparison instead:

Not bad for a Mask from a JPG.

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In your case once you learn the technique it shouldn't take more than a few minutes. Without using my Wacom I pushed the colors, created an alpha mask, burned the inner portion, and dodged the outer portion then used it as a mask for a simple curves adjustment.

Answer 3

Grey is not a colour; it is a step along the line of zero hue (that is, the black↔white line). You can't use a colour modification tool to change "dark white" to "normal white", because the hue is the same in both cases.

Before proceeding with your photo manipulation, you should read up on the difference between Hue, Saturation and Brightness. Then you will be ready to adjust these values independently to achieve your desired results.