HDR Troubleshooting: Halos and Ghosts
The number one way to ruin a good HDR image is the dreaded halo, and the second is ghosting artifacts. Your photos might be perfect, but they don’t need halos to prove it. The figure illustrates a nice view off an old walking bridge on the river below with a nice sky and clouds above.
What do you see in the ruined image (left)? Halos — around the structure of the bridge and the tree line.
What typically happens is that you’re focused on achieving a certain look in other areas of the photo that you either miss or ignore the fact that you’re ruining the entire thing by leaving in halos.
The image on the right side of the figure shows an alternative — tone mapped and processed to create a similar look without the halos. Much better! There are certain compromises, of course.
The sky is brighter and the structure darker. It looks closer to a realistic scene, but still not without drama. If you wanted to bump that up a notch, you could further increase contrast and do some dodging and burning in post-HDR editing.
If something is moving in your image and creates ghosting artifacts to the point of becoming a distraction, take it out or mask it. Don’t let it dominate the final image.
The top image in this figure was cropped from a scene with traffic moving up the road. It’s an interesting scene, but it has ghosts galore. (If you’re into math and physics, it is a good illustration of speed, time, shutter speed, and frame rate.)
Had this been at night or had the ghosting been more “river like” (with a constant stream of cars instead of a stop-start-stop appearance) it would probably be worth leaving the ghosting in.
The version without ghosting is also shown on the bottom of the figure. The truck is solid and contributes to the image. This was achieved when creating the HDR (ghosting options) and also by overlaying solid traffic over the ghosts (masking and blending).