Join Tim Grey for an in-depth discussion in this video Removing ghosts, part of Learning HDR (2012).
Because an HDR image is comprised of multiple individual frames, if anything at all is moving within the scene, there can be some problems with ghosting. In other words, you'll have part of a subject in one area, and part of the subject in another area. Or you might have the subject multiple times with some fading effect, a ghosting effect. In this particular photo, of course, you might assume nothing would be moving at all. After all, it's a photograph of statues in a plaza, with some buildings nearby. And yet, if we take a closer look, we'll actually find that there were some moving subjects in this case, specifically, some pigeons that were on one of the statues.
And you might also notice that we have a ghosted pigeon. So we have one pigeon that appears pretty much normal, and another pigeon that is just a faint glow here. We've got just a faint shadow of the pigeon, because this pigeon was moving around during the exposures and so it was in a different position for each of those exposures. But in HDR Pro, we're able to remove those ghosts. I'll turn on the Remove Ghosts checkbox. And we can see that that ghosting has now disappeared, so now we have just the one pigeon without that ghosted pigeon over to the right of it. In this case, the pigeon was moving quite a bit and so in each frame it's actually in a different position.
In some cases, just with it's head turned and in other cases actually moving around the statue a little bit. When you turn on the Remove Ghost option in HDR Pro, it needs to use a single frame as the key frame for determining where the object should be. In other words, which area of the image represents ghosts. That key frame is identified with a green box around it, but we can also change the key frame. If for whatever reason we feel that we want the moving subjects to be rendered in a particular position, we can switch to a different key frame.
So I'll go ahead for example, and click on the next frame to set that as the key frame. And once the preview updates, you'll see that the pigeon is in a slightly different position. You'll also note that the clouds moved a little bit. I'll go ahead and click on the next image as well, and you can see the pigeon turned its head. And we also have another pigeon, or at least a part of a pigeon over on the left side of the frame. So we could navigate among the various frames here to decide which frame we'd like to use as the key frame. And that will of course affect how the image is interpreted, and what the final result looks like. So, here, for example, we can see the head of the pigeon has gone missing. And so you can go through each of those frames and find which one represents the best key frame for that remove ghosts feature.
In this case, I think that exposure there, the one with the even exposure value, is probably the best option. So I'll set that as my key frame. But as you can see the Remove Ghosts option works pretty well. And we do have that extra flexibility of being able to determine which frame will be used as the basis of that ghost removal.
- Capturing, reviewing, and organizing HDR images
- Maximizing detail in a single image
- Simple single-image HDR
- Assembling from Bridge or Lightroom
- Choosing a conversion mode
- Using presets
- HDR Pro adjustment options
- Using Nik HDR Efex Pro
- Using Photomatix