How Many Exposures Do You Need For HDR ?

Condensation X - Prelude

1 exposure

scenes like this won’t benefit from HDR

Incubation II

 3 exposures

scenes like this may be made with 1 exposure but benefit from more

Antarctica CXXX

5 exposures

scenes like this require HDR

How many exposures do you need for HDR images?

It depends.

It depends on the contrast ratio of the scene you’re photographing.

And, it depends on how many corners you’re willing to cut.

There is a case to be made for rendering all images with bracketed exposures. If the best data in a file is in the top stop of the dynamic range of a camera, then making one exposure per stop of dynamic range in the scene, each weighted to the top stop pf the camera (ETTR), will give you ideal data in every stop of the rendered scene, once the exposures are merged. So, ideally, you’d make one exposure per stop of dynamic range in the scene. In your first exposure place the shadows in the top stop of the histogram (to the right), without clipping. Then in subsequent exposures reduce exposure in one stop increments, making a new exposure each time, until the highlights are placed in the top stop without any clipping. Then stop.


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Quick Answers To The 5 Most Asked HDR Exposure Questions

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hdr_3
How many shots do you need to make an HDR merge?
The most common answer is three.
The real answer is … it depends. First, it depends on the contrast ratio of the scene. Second, it depends on the exposure value (EV) increments you use between exposures. Third, it depends on the camera you use.
Many scenes only need 2 exposures. Most scenes need 3. Some scenes need 5. Only a few scenes need 7 or more.

How far apart in EV (exposure value) should separate exposures be?
1.5 stops. (Really any value between 1 and 2 stops.) While you won’t get better image quality if you use more shots separated by less exposure value (less than 1 stop), you also won’t compromise it. While you can also use higher increments (more than 2 stops) be careful – you may produce banding in smooth areas, particularly those with gradations.

Do you need to make HDR merges more frequently with some cameras and less with others?
Yes. Cameras that have a greater dynamic range can capture a higher contrast ratio and so don’t require HDR bracketing as frequently. While this can make a difference for images that would require two and occasionally three shots, for scenes with more extreme contrast ratios HDR merges will be necessary for all cameras.


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