Rapid HDR Captures


Today’s Question: In your GreyLearning Series on Optimizing Photos, in the lesson on HDR images you had a series of six captures ranging from a dark exposure to a light one. The sun was in the frame. My question is how did you make six captures with different settings without the sun moving, or apparently moving?

Tim’s Quick Answer: The key when including the sun (or moon) in the frame when capturing a series of exposures for a high dynamic range (HDR) result is to capture those exposures quickly using automatic exposure bracketing (AEB).

More Detail: While the sun and moon don’t seem to be moving all that fast across the sky to the unaided eye, they are certainly moving. In the case of the sun the rate of movement is about fifteen degrees per hour. That still isn’t incredibly fast movement across the sky, but it does create a risk that if you capture bracketed exposures that include the sun or moon, there could be a change in position for the sun or moon from one frame to the next.

Automatic exposure bracketing enables you to capture the various exposures as quickly as possible, minimizing the risk of movement between frames.

The specifics of how you employ automatic exposure bracketing will vary from one camera to the next, and not all cameras support this feature. In general, you will enable the bracketing via menu settings, where you can set the number of exposures to bracket and the number of stops between exposures. Two stops of separation between exposures works well for HDR bracketing.

With many cameras in addition to configuring the bracketing settings you’ll need to use a timer for the bracketing to be completely automatic. For example, you might set a 3-second timer so that when you trigger the exposure the bracketed captures will all be taken in rapid succession.

And, of course, to some extent HDR software can manage minor variations from one frame to the next.

For those interested, the HDR image in question was a sunrise photo of an abandoned homestead farmhouse in the Palouse region of eastern Washington State. You can see the photo on my Instagram feed here: