HDR Photos are created by merging two or more exposures together to show the entire dynamic range of a scene. This is an great tool that we explore fully in our HDR Learning Center. The challenge is a moving subject.
Ghosting
Ghosting happens when something moves during the exposure brackets. Leaves on trees blown by wind, waves on a body of water, cars moving on a roadway or in this case, camera movement causes multiple images–ghosts–in the photograph. The wind farm below is a great example of ghosting.
The original HDR is on the left. The deghosted one is on the right.
The windmill is a great example of ghosting in an HDR assembly. The blades were moving during the three exposures. The extra blades in the left hand photo are from the position of the blades during the bracket. Selective deghosting in Photomatix is an easy way to remove the extra blades. Here’s how.
Load the bracketed images
Here’s how to process your HDR image using Photomatix.
- Launch Photomatix Pro.
- Choose File > Open… The Photomatix Pro dialog opens. Click Load Bracketed Photos (1.)
- The “Select Bracketed Photos” dialog opens. Click Browse… choose the photos to be processed then click Load.
- If you want to view the 32-bit unprocessed file check the box. Click OK.
- If you dragged photos onto either the Photomatix icon or into the gray area in the Photomatix Pro dialog, the Select dialog shows up displaying the selected photos.
Align & deghost
Now it’s time to merge the images. Clicking OK above brings up the Merge to HDR Options dialog.
- Check Align source images (1.)
- Choose taken on tripod or hand-held (2.)
- Check Show options to remove ghosts ( 3.)
- Check Reduce chromatic aberrations (4.)
- Click Align & Show Deghosting
Photomatix offers two deghosting options–automatic and selective. Here’s what they do and when to use them.
Automatic Deghosting
The Deghosting Options dialog starts with the choice between selective and automatic. Automatic is great for very small ghosts like moving leaves and waves. Begin by selecting one of the exposures to act as the base for the deghosting. Move the deghosting slider to about 50%. Click through the exposures. Are the ghosts gone? If you find the slider has to be moved into the higher ranges, be aware the possibility of creating artifacts in the final HDR is real. That’s when to check Selective Deghosting.
Avoid high automatic deghosting settings to avoid artifacts.
Selective Deghosting
This is Photomatix’ recommended method. It’s easy to use. Draw a selection around the ghosted area. Right click inside the selection then choose Mark selection as ghosted area.
Choose the base photo
The base photo for deghosting can be chosen in Selective Deghosting. It’s a little hidden. Once an area has been marked as a ghosted area, right click in it. Two choices appear Remove selection and Set another photo for selection. Choose one then click Preview deghosting. Repeat with the other brackets to see which one does the best job of deghosting. When you are happy with the deghosting click OK to proceed to creating the merged HDR.
When the camera moves…
I shot this for HDR using a two stop under, normal two stop over bracket. It was late afternoon. Golden light was hitting the yellow locomotive. The exposures with my new Canon 5Dsr were all at ISO 100 @ f4.5. The shutter speeds were 1/10th, 1/30th and 1/125th respectively. I did not have time to put up a tripod. I knew as I was shooting that the camera moved during the bracket. I opened the three exposures in HDRsoft’s Photomatix. Even with Photomatix’ great auto-alignment feature, there was still a slight but noticeable difference of camera positions among the exposures. This is also a job for Selective Deghosting
The arrows show the ghosted areas.
Draw the selections
I made a selection around the front of the locomotive and one around the weeds in the left foreground. I marked the selection as an area for deghosting by right clicking and choosing to do so. Below in the left hand photograph, you can see the how much I had moved the camera during the bracket. The right hand one shows what a great job deghosting does in Photomatix. I love Photomatix for converting my exposure brackets into HDR files. You can download a trial that never expires here. A watermark will appear on all of the images until a license is purchased.
Never shoot on railroad tracks
Before I get my chops busted for shooting on train tracks, rest assured I know it’s super dangerous. What’s not shown in the photograph is the railroad crossing. It has both gates up in the open “there’s-no-train-coming” position. Car traffic is passing through the intersection right behind me. The train in the photo is parked. It’s not moving. If it were moving or was going to move, the crossing guards would be down. I’m standing on the edge of the right of way. Technically, my right foot is guilty of trespassing. I waved at the engineer, holding up my camera. He gave me a thumbs up gesture through the window. Anyway. Don’t shoot on train tracks. Ever. Get more info from Operation Lifesaver.
Kevin is a commercial photographer from Atlanta. He works for fashion, architectural, manufacturing and corporate clients. When he’s not shooting, he contributes to Photoshop User magazine & writes for Photofocus.com.
Click here for a list of Kevin’s articles.
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Photographs in this post are by Kevin Ames. ©2015 Kevin Ames ~ All rights reserved.
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