Will an ND filter/long exposure increase dynamic range?

Tom Pinchenzo

Tom Pinchenzo

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Tom
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It’s something I’ve sort of thought has been the case from using ND for long exposures (I don’t mean grads as they obviously do this). I’ve noticed histograms fitting nicely in the middle when I’ve expected to struggle with dynamic range. Then I saw an article that mentions ND filters helping with dynamic range. I can’t see how it would work but then again I don’t understand how sensors work...
 
Using Grads does not increase the DR of the camera but can reduce the DR of the scene. Perhaps with the long exposures you are referring to the long exposure noise reduction. This is when photographing night skies thus needing a long exposure. The sensor can heat up during this time thus reducing the DR and certainly adding more visible noise. The technique is to take two long exposure one of the scene and one with the shutter closed thus capturing the noise. This noise is not entirely random so can be reduced in the wanted image by subtracting the noise. Some DSLR's have this built in (mine does but I have never used it as I am not an astrophotographer). You would certainly NOT use an ND as you need all the light you can capture. So no, ND filters do not increase the camera or image dynamic range.

I personally do not use Grads as they deteriorate the image quality and darken parts of the image you may not want darkened. If the scene is within the DR of the camera then capturing with a Raw file will do the job with a modern camera. If the DR of the scene exceeds the camera DR just capture multiple exposure and combine; this latter process does increase the DR of the image. With my current DSLR having a DR of almost 14 stops most landscapes will fit so no benefit in using a Grad anyway.

Dave
 
Depends on the subject. Take a broken waterfall, or a choppy sea, with bright light or possibly direct sunlight. The very brightest spots visible on a short exposure are likely to be superimposed by darker tones in a long exposure, so those areas of the image will be less bright. Thus the overall dynamic range will be less. I use this routinely when taking long exposures under 'challenging' conditions.
 
sk66 said:
No. Pretty much everything we do (ND, raw file recovery, etc) is to reduce DR in order to fit w/in some limitation farther down the line (sensor, monitor, printer, etc).
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Sorry, this is what I meant - increase the DR the camera will be able to capture.

JohnFar said:
Depends on the subject. Take a broken waterfall, or a choppy sea, with bright light or possibly direct sunlight. The very brightest spots visible on a short exposure are likely to be superimposed by darker tones in a long exposure, so those areas of the image will be less bright. Thus the overall dynamic range will be less. I use this routinely when taking long exposures under 'challenging' conditions.
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Aha, this makes sense. I've noticed it on seascapes and where there are clouds moving across the sun etc. The lights and darks where there is movement will be averaged out. Thanks - in hindsight seems fairly obvious.... :rolleyes:
 
Tom Pinchenzo said:
Sorry, this is what I meant - increase the DR the camera will be able to capture.
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The answer is still no... an ND only shifts which parts of the scene fall within the camera's DR capability at that ISO. I.e. it makes both bright areas and dark areas darker; bringing more bright areas within the max capability, and dropping more darks below the min capability. If there are no dark areas to drop below min, then the scene didn't exceed capability to start with.
 
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sk66 said:
The answer is still no... an ND only shifts which parts of the scene fall within the camera's DR capability at that ISO. I.e. it makes both bright areas and dark areas darker; bringing more bright areas within the max capability, and dropping more darks below the min capability. If there are no dark areas to drop below min, then the scene didn't exceed capability to start with.
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John’s answer explains what I’ve noticed with long exposures, where you might have lights and darks in say, a choppy sea, and the long exposure averages them out to a somewhere in the middle. Or if you have bright sun and cloud shadows moving across a landscape then they’re averaged out.
 
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