HDR - Whats the Optimal Number of brackets and increments?

[jamesev]

Is there an optimal bracketing setting for HDR?

I use the D300s which has the AEB setting and am not sure whether to try 3/5/7/9 brackets or what increments 1ev / 0.7ev / 0.3 ev (obviously there are limitations ie 1ev increment for a 9 bracket)

A fair number of people seem to go with 3 (although am not sure if this is because other cameras don't have the AEB function) or there is a "better" result if only 3 brackets are used?

Any advice would be appreciated

[Elmo]

From a purist standpoint There is no "optimal" number or values for exposure. HDR stand for High Dynamic Range. That means it is a process to increase the dynamic range of an image. A simplistic definition of Dynamic range is the difference in exposure between the lightest and darkest part of the scene (no the captured image).

The "average" dynamic range of most digital cameras is about 7 stops. A sunlit scene can easily contain over 12. So if you make three exposures +2,0.-2 you have increased the possible dynamic range by 4 stops (still a little short of the scene value), but worse the dynamic range might not be centered around the average exposure.

As we generally work in an 8 bit world (Computers) our reproduction is limited to 8 units of dynamic range. What our capture and processing needs to do is compress the actual dynamic range of the scene to 8 stops. To do this the brightest part (pure white) needs to have an exposed value of +4 stops while the exposed value of the pure black needs to be at -4 stops. In reality i find these values still tend to appear to have blown out whites and blocked up blacks. So i aim for +/- 3

To accomplish this I meter a pure white area and assign an exposure for that area at 3 stops less. Likewise I meter a black and assign an exposure three stops more. This gives me the two extreme exposures. Most times I then expose in one stop increments to fill the difference.

This gives a good start but I have found that all too often this gives a true representation that is not ascetically pleasing and I need to have smaller steps on one end that on the other to balance the scene. This scene is about 16 stops from interior to exterior and required packing the lower values.

[jamesev]

So would that mean that generally To get High Dynamic Range it would be better to get say

3 Shots at -1, 0, +1 than at -.3, 0, +.3 or
5 Shots at say -2, -1, 0 , +1, +2 as that would give more range

??

[Elmo]

I am not trying to avoid your question, but for me that is like asking what is the best shutter speed or what is the best f-stop. The answer is what suits the conditions. I can only make this suggestion. Shoot one scene using several combinations. Process them all to see which gives the result you like. Then do the same with another scene and you will be able to determine what suits your taste best.

So in closing I will add that I have observed that a lot of folks shoot at +-2 and take what they get.

A +-2 shot just for color mapping

[OsmosisStudios]

You should really only ever need 2 images, MAX 3.

[jamesev]

Originally Posted by Elmo

I am not trying to avoid your question, but for me that is like asking what is the best shutter speed or what is the best f-stop. The answer is what suits the conditions. I can only make this suggestion. Shoot one scene using several combinations. Process them all to see which gives the result you like. Then do the same with another scene and you will be able to determine what suits your taste best.

So in closing I will add that I have observed that a lot of folks shoot at +-2 and take what they get.

A +-2 shot just for color mapping

Not at all, any advice / opinions are more than welcome...and greatfully received

[inkista]

To me, the optimal number of images & intervals is whatever you need to cover the dynamic range of the scene completely. I disagree with OS's assertion that you'd only ever need two images with 3EV between them. I've bracketed three images at 2EV intervals, and still not covered the full dynamic range. Sometimes you need more, sometimes you need less. If you can light properly, you may not need any.

This is an "it depends" thing. It depends on the scene you're shooting. Some scenes don't need HDR. Some do. Some have more dynamic range than others.

One easy way to see if you've covered the full range is to check your histogram. Until you see extinction (i.e., values going down to zero) at both ends of the histogram, you haven't covered the entire dynamic range. Sometimes you can see it in a single shot. Sometimes it takes two. Sometimes it takes three. Or five. Or seven. Or nine.

Canon shooters will often bracket three shots at 2EV intervals, because that gives the maximum dynamic range coverage that can be done handheld in burst mode (unless you have a 1-series camera), and often it's "good enough." But that doesn't mean it's optimal.

[RichardTaylor]

Have a look at the book;
Practical HDR by David Nigtingale.
ISBN 978-1-905814-63-3
Publisher is ILEX press.

Chapter two has some great info re shooting for HDR.


From my own experience when shooting for HDR (I havn't ended up using it because I felt I got better results by merging images my self) that shooting at anything less than 1 stop apart was a waste of time.

[Krusty79]

Good question on a topic we take for granted. To me, that also raises the question - if +2 and -2 is enough to cover the dynamic range in a shot, then is it better to shoot (-2, -1, 0, +1 +2) or (-2, 0, +2)? It seems like -2, 0, +2 is what I see used the most.

[ravncat]

I am of the school of thought of 2, maybe 3. One for the highlights, one for the shadows - measure the range. You should have enough for the mid-tones in between. If the range is too far apart, you may need a third midtone shot.