Photoshop Top 40
Illustration by John Hersey

24. Curves


Photoshop Top 40

with Deke McClelland

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Video: 24. Curves

(Music playing) Deke's Photoshop? Deke's Photoshop? Top 40! Feature #24 is Curves and Curves is the pre-eminent luminance adjustment feature inside of Photoshop. That is to say it is the most powerful feature of them all where luminance adjustment is concerned inside of Photoshop Proper. You might argue that you have even better control instead of camera raw, but where Photoshop is concerned this is as good as it gets. And what you can do is you can adjust your luminance that is your highlights, your shadows your mid tones and so forth you can adjust the brightness of the image at a level by level basis.
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Watch the Online Video Course Photoshop Top 40
7h 13m Intermediate Dec 21, 2009

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There's nothing people love more than lists, and Photoshop Top 40 offers a great one, highlighting the best features in Photoshop. Deke McClelland counts down to #1, detailing one great feature after another in this popular digital imaging application. The videos cover tools, commands, and concepts, emphasizing what's really important in Photoshop.

Topics include:
  • Assembling multiple pieces of artwork with layer comps
  • Creating a black-and-white image from a color photograph
  • Merging multiple channels to create an alpha channel with calculations
  • Selecting images with the Pen tool
  • Masking images using the Brush tool
Design Photography
Deke McClelland

24. Curves

(Music playing) Deke's Photoshop? Deke's Photoshop? Top 40! Feature #24 is Curves and Curves is the pre-eminent luminance adjustment feature inside of Photoshop. That is to say it is the most powerful feature of them all where luminance adjustment is concerned inside of Photoshop Proper. You might argue that you have even better control instead of camera raw, but where Photoshop is concerned this is as good as it gets. And what you can do is you can adjust your luminance that is your highlights, your shadows your mid tones and so forth you can adjust the brightness of the image at a level by level basis.

So you have quarter tone control and three-quarter tone control and so on and you don't have to know what any of that means because you're just editing points inside of a graph. Now it does demand a pound of flesh. It is one of the harder functions to use inside of Photoshop. But my goodness is it capable? And so we are working in an image from the image vendor Fotolia and it comes from photographer Mike Watson. So some of the images end up costing more if you're willing to invest in a classic stock photography image then you can and they are available there, and sometimes you get what you pay for.

In other words, in this case this is a beautiful image of this model set up against a snowy background. My goodness is she shivering. Now here's the thing though. I'm not that keen on the degree to which this is a high key image. In other words, it's quite blown out and you might argue well that's good because you know we have a snowy background. We want to impart the frosty mood but I figure this image could have a lot more heft to it if we deepen some of the highlights and the mid tones and that's what we're about to do. Now I am working inside of Photoshop CS4, if you're working inside a Photoshop CS3 or earlier then things will work a little different and I'll try to keep you apprised of the differences here.

For starters, if you're going to apply a Curves adjustment layer you would go down to the black white icon and choose Curves. That works across all versions of the software, however since I'm working inside of Photoshop CS4, I'll go out to the adjustments palette and I will Alt+ click or Option+ click on the third icon in the first row right there which is Curves and the advantage of Alt clicking or an Mac Option clicking is that I can name a layer as I create it so I go ahead and call it heft because that's what I'm trying to add to this image, and I will click OK. And now we get the big old Curves interface here inside the Adjustment palette.

Now when I say big old, I mean by default it's small, actually it looks like this. I will go ahead and click on this icon here, in order to reduce the size of this Curves graph right there. That's no good, you want a big Curves graph because right now we're seeing a graph of indeterminate width and height, I don't know how many pixels are involved here. But what you want is 256 pixels wide and 256 pixels tall because that gives you control over every point inside of your standard eight bit per channel image and that's the metaphor that Curves uses.

So, in order to get the big graph which you'll need you click on this little folder icon with the arrow on it again this is only inside of Photoshop CS4, you don't have to worry about it in older versions. You'll be working inside of a dialog box it's already properly sized. All right, so we're working inside of an RGB image as presumably you will be inside of Photoshop, most of the time every once in a while you work in CMYK or some other color mode. But right now I am working inside of an RGB image, and by default when you're working with RGB, you will see here is a graph of all the luminance levels inside the image ranging from black over here in the left to white all the way in a right-hand side of the graph.

And we're also seeing -- everything in between is in between so black is over here white is over here. And we have this histogram that's showing us the balance of power, where the luminance levels are concerned inside of this image. So we don't have much in a way of shadows. The shadows are going to be over here on the dark side of the graph, the left side. The highlights are going be over here in the right-hand side. There are a lot of highlights inside the image, no surprise because it's so very bright and then we have a fair amount of mid tones in between in the central portion of the graph, and that's what we're seeing this is a bar graph of all the luminance levels inside the image.

This is what we're seeing inside the graph. Now if you want to change the balance of the image, then what you do is you click somewhere along this curve. Now, I know it looks like a straight line that's the way it start but it wants to be a curve, and you curve it by clicking some place inside the line and I typically, you know when in doubt just click right there in the middle and I'll click to set a point there and that's going to be mid tone point and then if I want to light my mid tones, I drag upward because we're basically mapping the luminance levels We're Mapping the existing ones that are measured horizontally with the presumed ones, with the ones we are looking for which are measured vertically, starting with black at the bottom and going up to white at the top.

So in my case I'm saying what was a medium gray essentially, an absolute mid tone I want it to become much brighter that's why I am dragging it upward and I'm making all the colors inside the image brighter as well. Depending on how close they are to either being black or white. You can see the black and white remained fixed. So that I'm not clipping any colors inside my image. Now this is not the effect that I want so what I would do instead is I would go ahead drag that guy down in order to darken it up. Again, I am mostly affecting the mid tones but I'm affecting the shadows and the highlights to an extent as well.

Now, if I want to gain independent control over the shadows and highlights then I would create additional points. For example, I'll go-ahead and click on a point here inside of the highlight region, adding a point doesn't do anything. It just gives you a significant point that you can then modify here inside the palette. And now I'll go ahead and drag it down in order to darken up the highlights independently of the mid tones and the shadows. Notice that the shadows are actually growing lighter at this point because this mid tone point is serving as a fulcrum. So as I drag that highlight point up, the shadows sink a little bit as I drag that highlight point down the shadows raise a little bit.

If I want to raise them a little bit more I could click to set a point and then I could adjust it as well, and you can adjust these points from the keyboard. So just press an arrow key in order to move, if I press the right arrow key, I am going to move the point to the right and left arrow key is going to move it to the left, and why that's significant that's obvious, I know you know your right and your left there or at least most of you do presumably. Why that's significant is the left and right arrows are changing the input value that is luminance level that you're mapping in the first place, and then the up and down arrow - so the up arrow key is going to move the point up the down arrow key is going move the point down.

That's changing the output value here. That is the luminance level 2 which you are mapping this existing luminance levels inside the image. So the degree to which you are changing the shadows in my case. All right, so that's one way to work. I'm going to clear all that stuff because I want to show you few other things you can do. And I'll clear it out by clicking on this reset to adjustment default button, which doesn't exist inside CS3 in earlier. What you would do inside CS3 in earlier is you would press the Alt key or the Option key in the Mac and you would click and what was formerly the Cancel button is now the Reset button.

So weird but that's the way it works, anyway I'll just click on this button here in order to clear things out. And the reason I am clearing things is because I want you to see that there's some other tricks that are available to you. Now they are all kinds of micro-tricks. For example if you're working inside of CS3 or you are working inside the dialog box of the CS4, you can move your cursor outside the dialog box. It'll change to a little eyedropper and then you can drag inside the image, to see a bouncing ball move inside the graph. Now it's confusing for a lot of folks what in the world has happened to their bouncing ball inside of CS4, you can get to it either by going to be standard eye dropper tool, and then you have to Press and Hold the Ctrl key or the Cmd key on the Mac and then you can drag around and you'll see the bouncing ball.

That you'll see up there in a highlight region in the upper corner of the Adjustment palette graph right there. And that's because I have the Ctrl key down or the Cmd key down on the Mac. Now that's just a bizarre trick in my opinion, especially because as soon as you release you are going to add a point at that position and that's an old school thing that works inside CS3 as well. If you Ctrl click or Cmd click, you are going to add a point at which you click to the composite graph. All right I'll undo that modification just by pressing Ctrl +Z or Cmd +Z on the Mac.

The other thing you can do here inside CS4, because you can't just move your cursor out here unless some special tool is selected and the eyedropper isn't really the most flexible solution here. The better thing to do is to grab this new target adjustment tool. This is the third time we've seen it now. We saw it for black-and-white when we looked at feature #36, and when we looked at feature number I forget what, but it was hue saturation. It had target as well inside CS4 in later and so does Curves. Curves is the other adjustment feature that has this tool available to it.

Go ahead and click on it and then you can see if you just move the cursor around, I'm not dragging I am just moving, I get the bouncing ball. So I can see the bouncing ball there inside the graph. Now what's really great about this tool is now I can just Click and Drag to change a color inside the image, to change the luminance level, and notice my little tool cursor is showing me that I drag up and down. So its physical appearance is always giving you a clue to how it works. So I going to go ahead and drag for example, inside of her shoulder and notice that sets a point, look over there in the right side hand of the screen I can't point to it for you.

I am actually pointing in space right now but you can't see me. But over there on right inside of the graph, you can see that it created an anchor point there, and now if I drag down I am going to move it down. I am just dragging down inside the image over here on her shoulder and then if I drag it up, I am going to move that point up as well. So I can actually just drag points inside of the image and this changes Curves. In my opinion, this one tool takes what was formerly a very complicated command, takes a while to wrap your brain around how it works and turns it in to a puppy dog.

It is so easy to use because all you have to do is grab this tool and then start dragging around inside the image, so I might say you know this little sort of gray shade that wants to be darker, so I click and drag inside it there and I'll drag downward like so and that does darken things up. And then if I decide, you know what, I want to adjust this point a little bit, I'll drag it down and to the left a little because I am modifying both the input and the output levels. And then you could drag someplace else like in some sort of shadow detail that you want to raise. Maybe you want her eyelashes to be just slightly brighter or something along those lines.

Anyway I'm going to drag these around quite a bit in order to add that heft that I was telling you about. I think it's so necessary to the success of this image and I think this looks a fair amount better here. Now, to just give you a sense, this is the before version of the image which now by comparison looks totally, ridiculously, obscenely blown out, by comparison to my corrected version of the image. However, one of the problems is and you'll run into this with Curves if you try to make these sorts of radical adjustments and you do have this amazing level of control.

You can drag these points willy-nilly. I mean you can do this number right here, if you want to so that you apply fairly preposterous correction to the image, if you so desire and this is frequently you'll hear these kinds of curve adjustments called Arbitrary Maps because we are arbitrarily Mapping the colors inside the image. Anyway I am going to go ahead and drag these points to more logical positions I think. Now notice how gray things are getting out here inside the central image window and that's because we have flattening occurring in the curve.

So a slope in the curve is a good thing anytime we start flattening things out we are going to see grays out here inside the image window. The reason is because we are taking what were formerly a bunch of different luminance levels and changing them to either the same luminance levels or very close neighbors. And so we are going to lose a lot of color definition. We are also going to lose a lot of just general definition inside the image. So that's not what I want. I'll go ahead and move things over just little bit like so I am liking this a lot better. But we still have a flat region right here and if that's bothering you, if you are starting to see grays inside the image, and you should be bothered by that frankly.

Then go down to your Layers palette, assuming that you're working, and this works inside the Photoshop CS4, CS3, CS2, what have you, as long as you're working with an adjustment layer. Drop-down to the Layers palette and change the blend mode from normal to luminosity and that way you're not affecting the colors, you are just affecting the luminance information and you're leaving the color balance the same way it was before and as a result we are ending up getting some sort of chap details inside of her skin. It looks totally wonderful. And we have a little bit of posterization. That's because we've applied a big huge curve adjustment at this point.

But it looks a lot better in my estimation than normal did. There is normal which is something of a low color image, we are starting to lose a lot of color definition there. Anyway I am going to go ahead and switch it to luminosity and I am going to go ahead and back off this adjustment right there that mid tone adjustment, and I might take my shadows down just a little bit because we could stand to and sync those shadows. Now, based on that I think I'll take down my mid tones as well and I might even get a little more adventurous with my highlights not too much. I don't want to start crimping the graph if you end up getting kinks in your graph, you'll end up getting bad results out there in that larger image window.

But something along the lines of this right here is starting to look pretty good for me and then the true benefit of working with something like an adjustment layer is that in addition to modifying the points on the graph, you could also just change the opacity. So if you feel like you have gone too far with your adjustments, and let's say I have my marquee tool active then I could just press let's say 7 for 70% opacity here inside the Layers palette, in order to evoke the modification that you see before you now. And so just to give you a sense of what we've been able to achieve here in a very short amount of time just by dragging a few points around, albeit somewhat adventurously, here inside the Adjustments palette, we've managed to achieve this effect right here.

This is the before version of the image, quite bright, and this is the after version, a little bit more heft. Thanks to the tried and true power of feature #24 Curves here inside Photoshop.

Find answers to the most frequently asked questions about Photoshop Top 40 .

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Q: Is there a way to batch convert an entire folder of photos from the RBG color mode to the CMYK color mode without having to open and convert each individual image?
A: In the Actions panel in Photoshop, create an action that converts an image from RGB to CMYK. Then link to that action from File > Automate > Batch inside Photoshop.
Next, in the Bridge, select a folder of images. Choose Tools > Photoshop > Batch. Select the action inside the ensuing dialog box.
Or, in Photoshop, select File > Automate > Batch, and select the action and the folder inside the dialog box.
See also: Photoshop CS2 Actions & Automation, Chapter 2 “Action Essentials.”
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