Can you create HDR from studio flash shots when only flash power changes?
Asked 2/25/2021
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I’m shooting in a dark studio where the subject is lit only by flash. The camera settings stay the same between frames, and I’m varying only the flash power to capture different brightness levels for an HDR merge. The problem is that many HDR programs expect exposure information from the camera settings/EXIF, so the files appear to have identical exposure metadata. Can HDR software still merge these images if only flash power changed? If not, what’s the best way to shoot an HDR bracket in this situation?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
5y ago
2 Answers
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A solution is to alter the EXIF data of the photos to make the HDR software believe that the exposure is different.
Normally, a factor of two on the power (halved or doubled) should entail difference of one EV (in the EXIF, better translated as a change is exposure duration, since this doesn't change the DoF in case it matters).
The problem is figuring out how accurate are the flash settings.
Otherwise, on the camera you can sill change the aperture, and if you don't want to change the aperture you can change the ISO.
Originally by user75947. Source · Licensed CC BY-SA 4.0
user75947
5y ago
0
Generated from our catalog & community — verify before relying on it.
Yes—HDR is still possible, but many programs want known exposure differences between frames. If your software allows manual exposure offsets, enter them directly. As a rule of thumb, doubling or halving flash power is about 1 EV.
If your HDR software relies only on EXIF, you can edit the metadata so the files appear bracketed. A common workaround is to change the recorded shutter speed in EXIF, even though shutter speed doesn’t affect flash exposure in a dark studio.
You can also bracket with camera settings instead of flash power:
- ISO changes flash exposure and preserves depth of field.
- Aperture also changes flash exposure, but it changes depth of field.
- Shutter speed usually won’t change flash exposure if ambient light is negligible, though it can be used as an EXIF placeholder.
So exposure information is useful because the software needs relative brightness differences, but it doesn’t have to come from actual shutter changes. The key is knowing the EV offset between frames and using software that lets you specify it, or adjusting EXIF so the bracket is recognized.
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