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In this course, photographer Ben Long describes the concepts and techniques behind high dynamic range (HDR) photography, a technique used to create images that have a wider range between the lightest and darkest areas of a scene than a digital camera can typically capture. The course begins with some background on dynamic range, on how camera sensors detect shadows, and on the kinds of subjects that benefit from HDR. Ben then describes and demonstrates several methods of generating HDR images, starting with single-shot HDR, which relies on masking to subtly enhance the dynamic range of a shot. Next, the course covers multi-exposure HDR, which involves shooting several photos of a scene, each at a different exposure, and then combining them using software tools. Ben demonstrates how to use Photoshop and the popular Photomatix software to process HDR images whose appearance ranges from subtle to surreal.
In this course, we're going to look at three pieces of HDR processing software: Photoshop CS5, Photomatix, and HDR Efex. In this movie, I'm going to show you the process of merging and tone mapping in Photoshop. Then in the next movie we're going to merge and tone map the same images in Photomatix. And in the movie after that, we'll do it all again in HDR Efex. I think you'll see that each program has its own strengths in it. You're probably going to want to end up with at least either Photomatix or HDR Efex in addition to Photoshop.
All three of these applications are available for a free demo download. You can get Photoshop at adobe.com/downloads. That will give you the latest version CS5. Photoshop has had HDR Merge for a couple of versions, but CS5 is the first version where it's really kind of usable and it's pretty different than previous versions. So if you're using CS3 or CS4, you'll need to get 5 to follow along. We're not going to be taking these images all the way to completion yet. We're just getting them merged and tone mapped, so you can see how the process works in each application and what the controls are.
So let's start with Photoshop. As I do with all of my photo processing workflow, I start in Bridge and Bridge is a very good place to start for HDR also because it allows you to easily launch into different HDR processors. In the Chapter 5 folder of exercise files, you should find three images: 3714, 3715, and 3716. And we can see just by looking at them that they're a bracketed set. This one is my normal exposure, one stop under, one stop over.
So there are lots of different ways of launching HDR Merge in Photoshop. These are RAW images. I could just go ahead and open them. I'll do that and I get Camera Raw here. I don't want to make any changes to them in Camera Raw, simply because there's no need. I'm going to take all of the data in the images and merge it all into one big file. I don't need to adjust it in any way. So I'm going to select them all, which I did by hitting Command+A and I'm going to hit Open Images. And it's going to go through the RAW processing step, and I end up with three images.
Now if I go to File > Automate > Merge to HDR Pro, this brings up a Merge to HDR Pro dialog box, which is where I can pick some images to merge and there are a lot of different ways of picking them. If I wanted, I could tell them I'm going to pick some files and I can hit the Browse button and then navigate to the folder where those files are and simply select them and they would appear in this box. Or if I had already grouped the files into a folder by themselves so that those were the only things in the folder, I could pick Folder and then browse to that folder.
Instead, I'm going to say Add Open Files and that just adds all of the currently opened files to this list. I need to be sure that I don't have any other files opened of any kind and then I can hit OK and the process would start. There's an easier way of doing this though. I'm going to cancel out of here and I'm going to just close all of these documents. That's the long way. I can't really give you a reason to ever use that, unless you don't typically start your workflow in Bridge, would be one reason not to. I can launch into HDR Merge directly from Bridge though.
Simply select the images that you want to merge in Bridge and then go up to Tools > Photoshop > Merge to HDR Pro. I pick that and it simply starts the process. I don't have to go through any of the problem of trying to find images. So what's happening now is Photoshop is doing the RAW conversion for these images, opening them up, and automatically copying each one of these images into a single final document, wherein each image exists as its own layer. It then stops and shows me this.
This is the Merge to HDR Pro dialog box, and I see a nice big thumbnail here. And I see all of the images that I have selected and it's identified that this is the one that was exposed normally and this is an exposure value of +1. It's one stop overexposed. This is an exposure value of -1. This allows me to turn off or remove some of the data from my merge if I want to. So I can say well, don't include the underexposed image in your calculations. And you can see the image gets a little brighter. Honestly, I have never used these controls. I can't tell you why you might want them, unless you're finding that maybe you shot a 5 or 7 stop bracket and you're seeing some noise in the shadows, because your darker images have a lot of noise in them maybe. You could turn those off and try and control the noise that way.
These are the controls that we're interested in over here. By default, your dialog probably comes up looking like this, with Mode set to 16 Bit and a bunch of sliders here. I want you to take a look at 32 Bit for a minute though. What has happened is Photoshop has combined all three of those 16-bit images into a single 32-bit file. Now with 32 bits of color per pixel, we can hold far more colors than it's possible to display on this monitor. Or any monitor in existence.
In other words, this image has a tremendous amount of data in it. And I can see from my histogram here each one these red lines is a stop. One, two, three, four, five, six, seven, eight. I have got eight stops of dynamic range here, which is enormous. If I move this thing around, I can basically see a view of just different slices of my 32-bit data. So I can see that way down here I've got full detail in the shadows and way up here, if I want, I've got detail all the way down under here.
So I've just got this huge mess of data. So the slider lets me move around and look at it and it also determines what part of the data is going to be viewable if I save this image as a 32-bit file and open it up again later. Honestly, there's no reason to really ever use this. It's an interesting way to explore a 32-bit file, something you normally can't do on a monitor. It's not something you'll ever do in practice while you're doing HDR Merge. What you will normally do is switch over to 16-bit mode. We need to take that 32-bit mess of data and crunch it down to 16-bit color.
This is the tone mapping processes. This is where we are going to cherry- pick tones from different parts of that 32-bit range and map them back into our image. And I control that mapping process through these sliders. So let's just take a look at the image for a minute. We've got actually good dynamic range and I'm judging that simply by detail. I've got good detail here in the clouds, the brightest parts of the image, nothing looks really overexposed. There's still detail visible. I can see a little bits of graffiti way down here in the shadows of this image. So I've got a lot of good detail in here, but the image looks kind of flat.
It's a low-contrast image. And this is not an accurate histogram from my 32-bit final, but you can see that I don't have data across the entire 32-bit range of the file. And that's apparently holding true as we map it down into 16 bits. I'm not getting a full contrast range, so I can use these sliders to try and deal with that. Now with Photoshop and Photomatix, you never during the tone mapping process get the image completely finished. You can get it ballpark, but you always have to go in and do a little bit of extra work in Photoshop using Photoshop's normal tools.
So you'll be far less frustrated if you go into the process knowing that most of the time you cannot nail the image exactly the way that you want it. The other thing you should be ready for is these sliders do not work like sliders that you might be used to in other parts of Photoshop. For example, Gamma, in the Merge to HDR dialog box, if I slide it to the left, my midtones get darker. If I slide it to the right, my midtones get lighter, but my whole image just loses contrast. In the Merge to HDR dialog box you can almost think of Gamma simply as a contrast slider with more contrast appearing as you slide to the left. More is it the left, not to the right, which that's a little bit weird.
So that immediately punches up my contrast a little bit. Exposure does just what you think. It brightens or darkens the image. I want to leave it pretty much where it was. It had done a good job of finding nice balance of highlight versus shadow detail. I don't have any clipping in the highlights and I've still got good shadow detail. Detail is making a bunch of little micro-contrast adjustments. It's a little bit like sharpening, but you don't have to worry about overdoing it in the way that you do with the Sharpness slider. Now I can get a little bit of a crunchy effect like I could with a sharpening effect, but it's a little more fine, so that's a way of putting a little bit if texture back into the image.
Shadow lightens or darkens the shadows in the image and it's a very subtle. If I go to the right, I am lightening the shadows. So this again is a little bit backwards. Sliding to the right does not give me more shadow. It gives me less. It lightens the shadows. So I'm going to go back here to the left. I'm still just trying to get a little more contrast in. Than Highlight does the opposite. It lets me brighten or darken the highlights in the image, with more highlights coming to the right, less highlights coming to left.
And this slider actually works a little bit like you'd expect it would. Edge Glow has to do a little bit with that HDR effect that we're all used to. Let me just dial it up real high. If you ever get confused as to what these sliders do, a quick way to find out is to simply crank them to their maximum and see what's happened. It's a little bit hard to tell in this image. This is bumping up tones in a way that does tend to make them look like they're glowing and I usually keep these pretty low. Even if you're going for a real surreal kind of HDR look, it's very easy to push these too far and end up with overexposed highlights.
In fact, I'm just going to turn that off. Down here I've got Vibrance and Saturation. These are exactly what you would expect. Saturation increases the color saturation of the image; Vibrance increases color saturation while protecting skin tones. So flesh color usually won't turn all orange, the way that it does with the Saturation adjustment. Now something else that's nice is right here in the Merge to HDR dialog. I have a Curve control. So this can be a way that I can also try and put some contrast back into the image. And this is far more akin to the Curve control in Camera RAW than it is to the Curve control in Photoshop.
And what I mean by that is its tiny, tiny little movements of the curve give you quite a bit of adjustment, because we are working with such a data-rich image at this stage. So I'm just going to try and boost the shadow tones a little bit, but there we go. The highlights, so I'm going to pull those back down, and that gives me a little bit of brightness. Again, I'm not worrying if I can't nail this image exactly the way that I want it. I'm just trying to ballpark it. So these are the main controls. Now I have presets that Adobe has provided and so I can go up here if I want and use one of these as a starting place.
Honestly, I don't typically do that, because most of these are a little bit over-the-top for my taste. And even if you like a really over-the- top HDR look, these still aren't that great because as you can see, these bad halo problems. It just hasn't done a very good job. This stuff is really orange. We lost all those brightness in our sky. This stuff is punched up nicely, but we've got this halo around the car. So these presets are a little garish and honestly, Photoshop just doesn't do a great job with tone mapping yet, or at least the interface of their tone mapping is not quite there yet, so I tend to stay with the default controls.
I've lost the settings that I had dialed in earlier, but that's okay. We're not going to keep this image. You'll also find a pop-up menu here that says Local Adaptation, Equalize Histogram, Exposure and Gamma, and a Highlight Compression. You don't need to worry about these other three. these are legacy controls from earlier versions of Photoshop, they're very difficult to use, and none of them can provide you the quality of the results that you can get from Local Adaptation. So I would simply stay here and use these controls. When you're done, click OK to process the image, open it up in Photoshop, and then you're going to need to do more work on it.
And we're going to talk in detail about the type of work that you do to a tone mapped image later in this chapter.
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