[Crop] [Gutter] [Bent lines] [Dirt] [Curves] [Resize & Unsharp] [PNG Save]

Using Curves to get rid of dirt
in combination with history brushing

I have yet to meet an editor who uses Curves like I do, unless I told them how to do it. Of course, there are tons of editors whom I haven't met, so there's probably someone else out there who does this. Anyway, I shall now explain the wonders of Curves.

First let's take a look at Levels.

What levels shows is a representation of all the pixels in the image, arranged according to luminosity value, starting at 0 on the left and going to 255 on the right. Again, 0 is black and 255 is white. But take a look on the right side...there's a bunch of pixels in the range near 255. Most of this is the dirt—pixels that should be white but aren't quite. If I adjusted levels, however, it would affect the other areas of the page that currently look fine. It would be nice if there were a way to take all the pixels from 246 to 254 and give them the value of 255 while leaving the pixels from 245 and down exactly the same. Well, that's actually what you can do in curves, so that's what I'm going to explain.

When you bring up Curves, in the Image menu, submenu Adjustments, the following is the default box you're given:

Input and Output numbers are in percentages, with white in the lower left corner and black in the upper right corner, and a line you can add points to and drag up and down making a curve to adjust the luminosity values of the pixels. That's not a very useful thing for manga editing though. Here's how to make it useful.

First, click on the double arrow below the white area in order to put the black in the lower left and the white in the upper right, and to change the input/output numbers to luminosity values from 0–255 instead of percentages. Also click on the pencil instead of the bezier curve icon.

Additionally, if you are in Photoshop 7, click on the icon in the lower right of the window. This expands the box so you can access all 256 luminosity levels. (The old smaller box still works okay but it skips over some luminosities; the only way to affect them is drawing a line through adjacent values.)

I do curves in two steps, for reasons that I'll explain later. First I adjust the black end and hit OK. Then I go back in and ajust the white end.

First the black. In fullsize images I take everything from 21 down, or even up to 26 down, and give it a zero value. The pencil tool is what allows you do to this.



For this image I'm using 21 down. I move the pencil to where it says Input: 21 Output: 0 and click. Then I draw a line to the left until it says Input: 0 Output: 0. With the Preview box checked, you should be able to see what this does with the image. (Pretend you see a pencil there instead of a spinning CD....)

With the 21–0 line drawn, hit OK. Let's take a look at the effect on Levels. See the Levels box on the right—there are no pixels now registering with values from 1 to 21, because they were all changed to value 0.

And now I'll go into curves and draw a line running from Input: 246 Output: 255 to Input: 255 Output: 255 as shown. And hit OK. (A lot of the dirt will be darker than 246, but going below this could do more harm than good at this time. Sometimes I go to 241, but generally 246 seems to work well enough. The rest of the dirt I'll take of later.)

And now the levels dialogue shows no pixels of values 246–244.

Some of the dirt has now been taken care of, but it actually is helpful to have pixels of these values inside the tone areas. Time to whip out the history brush.

Bring up the history palette if you don't already have it open. The two curves should be the last entries. What I do now is make the final curve not apply to the tone areas.

I set the source for the history brush to be the state represending the black-end curve adjustment. This allows me to selectively undo the white-end curve in certain areas while leaving the effect of the black-end curve.

Now I select the history brush tool and look for areas that need brushing. Basically this includes anything that looks grey or other detailed screen areas, such as the area pictured to the right.

Using a 100% hard brush rather than a soft brush, I brush over the tone areas. The following picture shows in red some of the areas I brush over. (I do not use quickmask; this was just for the screenshot purposes.)

After I'm finished using the history brush, the Levels dialogue looks something like this...

This page is filling up so let's go to the next page where I will explain resizing, unsharp mask, and some more curves and history brushing.

[Crop] [Gutter] [Bent lines] [Dirt] [Curves] [Resize & Unsharp] [PNG Save]