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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.
Photomatix has excellent deghosting tools. Deghosting is the process of removing those semi-transparent ghosty artifacts that occur in a final HDR merge when something in your scene moved between frames. And we already did a Deghosting demo of these three images using Photoshop and we're about to do the same demo using Photomatix. If you didn't see the Photoshop version, let me just show you the images real quick. I'm shooting these kids and they had the nerve to move between frames, can you believe that? I went back when I was a kid and someone who was shooting a bracketed set of me, I knew enough not to move. But with these kids these days, I just don't get it.
Anyway, you can see his arms are flapping around there and his head is turning, and what that means is when I merge I am going to see ghosty arms and heads, and I don't want that. So let's go to it. I'm going to select these three images, drop them on to Photomatix, just like I normally would. Tell it to merge for HDR processing. These are the images I want to work with, and here I'm in my Preprocessing Options. I want to align. I want to reduce noise. I also want to remove ghosts. I have two options, Automatically or with Selective Deghosting, which they list as recommended.
I definitely recommend this also. Sometimes you get lucky with Automatic and it works, but the selective deghosting tool is so easy to use. There's no reason not to just do this somewhat manual process. So I hit the Preprocess button and it goes through a good amount of the HDR merging process that it would normally have to do, even if I was not Deghosting. It's reducing noise. It's aligning. When it's done with that, there's going to be an intermediate step where I'm going to have the chance to drive the deghosting feature before it does its final merge.
And here it is, this is the Selective Deghosting dialog box. Right off the bat, notice there's very good help information over here. A link to an HTML tutorial, a link to a video tutorial. You can look at those or you can just listen to me, and I've also got some written instructions here. It's pretty easy. First let's take a look at the ghosting problem. Look at this kid. He's got a little bit of an extra head, he's got a ghosting arm, he's got an extra foot, he's had better days. These two kids though while there are not obvious ghosting problems around them, but they are still suffering from some ghosting issues.
Their faces are a little bit out of focus because there are actually three versions. They moved very slightly. There are basically three versions of these two kids just stacked on top of each other. So I need to deghost all of three. Let's start with this one, which is very obvious. All I do is click and start dragging with my mouse and as I do, I leave this little bit dotted line, so I'm just circling this kid and as you'll notice I'm not being particularly picky or careful. What I'm doing with this process is just clueing Photomatix into where the ghosting problem is. Once I've circled him, I then Ctrl+ Click or right-click if I'm using a two-button mouse or using Windows.
And I get this popup menu. I can mark selection as ghosted area. When I do that, Photomatix now knows this is an area it needs to consider for deghosting. Now I could go ahead and circle the other two and head off to do my final processing, but I'm curious to know if this is really working, if I'm getting a good deghosting. So I'm going to preview Deghosting by clicking this button. It's going to think for a minute, and then bang, there it is. Look, his extra head's gone. His arms are sharp. His extra foot has gone. The pattern on his shirt has sharpened up, because there was some overlap there. That was leading to some ghosting effects that were basically just making for a soft focus.
I'm going to return to Selection mode, so that I can move on to the other kids because I'm satisfied with that one. If I did not like the way he turned out, I could simply right-click within this area over here and I'll just show you I can right-click right here, we're going to mark this as a ghosted area, and now I'm going to remove selection. That takes it off and now I can start over and I promise you I won't make that mistake again. I will finish this deghosting lasso here. Now I don't know if you noticed, but if I just let and go off the mouse button, it automatically closes it so I don't have to go all the way back up to the top again.
Again, I'm circling this kind of roughly. Mark selection as ghosted. Watch him very closely right in here as I click the Preview deghosting button. And there, kis his face just sharpened up. That one maybe a little harder for you to see in the small window size that this video will ultimately be presented. Circling the last one here and notice I'm now overlapping with the first one and that simply doesn't matter. Photomatix is smart enough to figure out which is which and how to separate all this stuff. So circle him, right-click, and Mark selection as ghosted.
You know, I trust that it's working well. I'm now going to bother previewing. I'm ready to just hit OK. Before I do that, let's take a look at these two controls down here. I can zoom in to try and get a better view. If I don't know where my ghosting is, this is a great way to get a quicker or a more detailed look. I have a Brightness control here. As you've probably already discovered with some of your HDR merge, it is very often they come out of the merging process very dark. That can make it difficult to see if you have a ghosting problem. So I can crank the brightness up just to make my image easier to see.
This is not a setting that will impact my final merge in any way. It's just a pre-visualization tool to make it easier for me to see any ghosting problems that I might have. So I'm going to hit OK and now it's extracting ghosting information. It's merging into HDR. Basically what it's doing, is it's doing its normal HDR merge process and then taking that extra deghosted stuff and layering that back on, blending it together, making sure that I have a very pretty image. There's the 32-bit version and then it immediately tone maps it into this.
And let's just zoom in here and sure enough, look there. He doesn't have a ghosting problem, he's very sharp, he has a little bit of a chromatic aberration problem. There are some purple fringing in here, some green fringing there. I can take that out in Photoshop. It sure looks good. If you dig around in this image though, what you will find is down here we have a noise problem. I can take care of that in post processing. I'm not going to worry about that now. This is zooming in pretty close, so I'm not going worry too much about whether that noise is even a problem until I do a print and see if it actually is an issue that needs to be fixed.
So that's deghosting in Photomatix. Play with it. Actually try and contrive some tests that force a ghosting problem, so that you can see how much you can correct it. Because once you know how much deghosting latitude you have, you might find that there are just more HDR subject matter out there for you. If you know, wow, this thing is moving quite a bit, but I got confidence that I'll be able to deghost it, suddenly you've got a wealth of new HDR material you can shoot.
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