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I've saved my progress as Composite B&W points.psd, so called because we've modified the black and white points for the composite image. It's found inside the 14_levels_curves folder. In this exercise, we're going to take a look at the Gamma Value, which allows us to adjust the Midtones in the image, while keeping the black and white points fixed. It's an essential option inside this dialog box and very useful as well. Now, I should tell you that I've reset a couple of preferences here. First of all, I went ahead and reestablished a Cache Levels value of 4, so that you and I are on the same page, assuming that you never changed your Cache Levels.
And then I've also reset my workspace to One-On-One, in order to tidy up my screen a little bit. I actually did that, to be honest, a couple of exercises ago. Now, notice over here, as a result of the new Cache Level's value, over here on the left side of the Adjustments panel, you'll see this warning, which is telling you that your Histogram is not entirely accurate. Now, I happen to know that I'm working from Cache Level 3 from investigating the Histogram panel, but that really doesn't matter. All we're concerned about is that this Histogram is inaccurate, we'd like to see an accurate one.
So go ahead and click on this icon in order to update the Histogram. The other thing to note about this graph is it's the before Histogram, that is, the one that's associated with the original underlying layer. If you want to see the after Histogram, the corrected one, then you need to bring up the Histogram panel, which I'll do by clicking on this icon in the panel Strip. Now, because I reset to One-On-One, I've got a dinky Histogram once again. I'll go ahead and enlarge it by going to the flyout menu, choosing Expanded View. Very important that your Source is set to Entire Image incidentally, so that you're seeing the composite version of the Adjustment layer, along with the original image, switching to Selected layer would be meaningless.
Also notice that I'm seeing the channel by channel Histograms layered on top of each other, whereas inside the Levels dialog box, you always see a composite Histogram. In order to switch to the Composite View, so that you're comparing apples to apples here, change Channel to RGB, and then of course because Cache Level is 3, go ahead and update that Histogram so that you can see the real thing. Now, notice that we have a bunch of vertical stripes inside of the Histogram. For example, if I click on one of these points, it's telling me that that's a level of 32, notice the Level value down here below the Histogram.
I'll go back to that point and there it is, the stripe at Level 32. And what that's telling is, is there are no pixels associated with a luminance level of 132 inside of this image. There are all kinds of pixels at 131 and they're a bunch of pixels at 133 as well, but we lost them all at 132. And that's what happens when you apply a Levels Adjustment. You're moving the luminance levels to new locations, and so you're getting to get gaps in between. That's probably not something you ever need to worry about, unless you really start overworking the image, that's when you may start to notice banding.
But the point I'm really try to make here is that, even though we're working with an Adjustment layer, that's happening. So we like to say that Adjustment layers are nondestructive, while in fact, they're really just editable. Once you apply them, they're just as destructive as Static Adjustments inside of Photoshop. So you're still going to get the same results if you apply these values inside the Levels dialog box or here in the Adjustments panel. Anyway, let's go ahead and hide the Histogram. What I'm noticing now is that my image is awfully bright, and what I'd like to do is tone down this big area of wall.
Now, this area clearly falls into the Midtones. We've got a few Highlights going on, a few Shadows as well, where these lines are concerned, and of course the Shadows inside the shutters here, but most of the other detail is Midtones. And you can modify Midtones by using either this gray slider or this numerical value below it. Now, this is known as the Gamma Value, incidentally. Now, the real purpose of the Gamma Value is to tweak the response of either a digital camera or your computer monitor or something along those lines, so that an image better matches the scene as you would have actually seen it, because your hardware and your eyes perceive the world in different ways.
And the Gamma Value here inside the Levels panel works the same way. Now, you can actually drag this gray slider one direction or the other. If you drag it to the left, you're going to lighten the Midtones in the image. Notice that the black value remains locked down. So you're not sacrificing your ultra dark colors inside the image. The white value remains locked down as well, so you preserve your Highlights. Now, if you go too far with this adjustment, the whole scene is going to appear washed out. And also, by the way, you really need to be aware of this phenomenon, when you overbrighten an image, you're going to bring out a lot of noise inside of your Shadows, so you really want to avoid that at all cost.
Anyway, I'm going to go ahead and zoom back out here, and center my image a little bit as well. So notice now that my Gamma Value set to 2.00, that's the adjustment that I've made so far. Compare that with the default Gamma Value of 1.00. Notice that, it's not that middle gray value of 128, it's this entirely different creature. And what it is, in case you're curious, it's an exponent. So in my case right now, I'm squaring the brightness of the colors inside the image. Where I'd reset this to a value of 1, then I would be sending the colors to the first power, which of course does nothing to them.
Anyway, values above 1 are going to brighten the Midtones, values below 1 are going to darken those Midtones , like so. And I also want you to see what's happening to the Histogram as we work, so I'll bring that Histogram panel back up. Let's go ahead and reset this guy to 1, and press the Tab key. So that's the Histogram we saw just a moment ago. I'll go ahead and update it, just so that it's a little smoother here. And then if I brighten the Gamma Value, notice that I'm stretching the Shadows like crazy, so they're hanging on for dear life over here, because they are anchored down at the black point, but that's why we're getting all this noise, because we're exaggerating the level of noise that was already there inside the Shadows.
And then we're squishing the Histogram over to the right hand side, and all of those black spikes right there are areas in which we are mashing a ton of pixels onto a certain luminance level. So for example, at Level 163, you can see that below the Histogram in the stats area, inside the panel, at a luminous level of 163, I've got an awful lot of pixels going now. But of course we're applying an over the top Gamma Adjustment at this point. If I move the Gamma Value over to the right, and again, this is an exaggerated adjustment, now the Highlights are hanging on for dear life.
They are anchored down at 194, and then they're getting stretched out like crazy over this area, so lots of gaps. And then over toward the left hand side of the Histogram, lots of spikes. Anyway, the value that I think works really well for this image is 0.9, and so that's what I'm going to set it to. And incidentally, when you're modifying the Gamma Value, here's what I recommend you do, not that you sit here and enter numbers of course, but rather, you start with 1 and then you can press the Up Arrow key to raise that value in .01 increments, or the Down Arrow key to lower it by a similar increment.
You can also, by the way, press Shift+Up Arrow to raise it in 0.1 increments or Shift+Down Arrow to lower it in 0.1 increments, and that's what I did. So I just clicked in the value, press Shift+Down Arrow and I ended up getting this result here. So the big difference, not a big difference actually, it's a tweak, but here's what the image looked like when we first opened it, so the face of the wall was a little bit too bright, and here's the way the wall looks now, a little bit more dim, a little bit more detail as well inside of that wall, because we have more contrast going on, thanks to our revised Gamma Value.
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