Can Darktable match background brightness across sessions using a sampled area?
Asked 8/8/2017
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2 answers
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I photograph subjects on the same fixed background in natural light. For white balance, I shoot a gray card, set WB from that test image, and reuse it as a preset for all images in the session.
What I’m still struggling with is keeping the overall brightness consistent, especially between different sessions as ambient light changes.
Is there a way in Darktable to sample a small area of the background and automatically adjust exposure so that area reaches a target brightness/exposure value? If not, what’s the closest workflow for getting more consistent exposure from shot to shot?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
8y ago
2 Answers
1
The closest thing I've seen in darktable is the automatic mode in the exposure module, see darktable manual.
Automatic adjustment is only available for raw images. A typical use case is deflickering of time-lapse photographs. You apply an automatic exposure correction with the same set of parameters to all images of the series – differences in lighting get compensated so that the final video sequence does not show any flickering.
But I would have thought the answer would be to shoot in aperture priority mode and let the camera's metering deal with small changes in ambient light by adjusting the exposure time. If the background takes up a enough of the image the camera's matrix / evaluative / ESP metering should be reasonably consistent, though for real accuracy a spot metered reading from the grey card for each image would be best.
Originally by user60903. Source · Licensed CC BY-SA 4.0
user60903
8y ago
0
Generated from our catalog & community — verify before relying on it.
Darktable doesn’t appear to offer a direct “sample this area and set it to a target exposure value” tool.
The closest built-in option is the Exposure module’s automatic mode, which can apply automatic exposure correction to RAW files. It’s commonly used for deflickering time-lapse sequences, where the same parameters are applied across images to compensate for changing light.
For capture, a better way to improve consistency is to let the camera handle small ambient-light changes: use aperture priority so the camera adjusts shutter speed as light shifts. If the background fills enough of the frame, matrix/evaluative metering should usually be fairly consistent. For greater precision, spot metering from the background would be more accurate.
So: in Darktable, the nearest option is auto exposure for RAWs; for best consistency, improve the exposure at capture with appropriate metering.
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UniqueBot
AI8y ago
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