Part I: Exposure Blending/HDR - Single File vs. Bracketed

Started Sep 11, 2009 | Discussions thread
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Chris Walden Senior Member • Posts: 2,394
Part I: Exposure Blending/HDR - Single File vs. Bracketed

Part I: Exposure Blending/HDR - Single File vs. Bracketed
Part II: Exposure Blending/HDR - Exposure Blending Methods/Software

FYI The dynamic range (DR) mentioned below pertains to the D300 sensor since it varies from camera to camera and shooting RAW.

I have had multiple conversations with Sem, Nick, Malch, Tammy and others regarding the DR captured in a single RAW file (8.8 stops of EV range, -4EV and +4EV) and if a single raw file was used to create virtual copies of varying exposures would the end result be the same as a bracketed shot of the same # of exposures. After all, the sensor captures almost 9 stops so just editing a single RAW file in post should produce the same result as 9 separate shots assuming the dynamic range of the shot is less than 9. Make sure you understand the underlined part because that is the essence of this post, Part I.

Lets first examine the working set of photos. The top row consists of a 7 shot bracketed photo. I chose this particular shot for a few reasons. #1 The DR (meaning the proper exposure of the highlights and the shadows) of this shot is greater than 7 stops and the moving water which makes aligning difficult on a bracketed shot or blurred subjects.

The bottom row takes the middle exposure of the top row DSC_6592.NEF and creates the same # of exposures from the single raw file. Take a look at the far right hand side and notice the difference in the shadows.

Now lets turn on Highlight (red area) and Shadow (blue area) clipping... This is a screenshot of the middle DSC_6592.NEF original on the left. Second shot we turn on clipping to see what is clipped in the original shot and showing the 'DR'. We can see that the red area shows highlight clipping in the sky and there is some shadow clipping in represented by the blue area. Third shot is adjusted -3EV from the single RAW file and from the clipping shown here we know that we cannot recover all the highlights, they are indeed blown and lost and the DR is outside what can be captured in a single RAW file. Fourth shot is +3EV and we can see there is very, very little clipped shadows. This shows the meat of this post... One would think from the area circled in Green that since NO shadow clipping occurs that we could produce the same level of detail here as the 7 bracketed shot.

I fully expected to see what is displayed in the red circles below, lost detail in the highlights. Since the DR was outside what the sensor captured (see above) and the highlights were blown out. But what I am not understanding is the area in blue... The shadow detail is much better in the blending of the 7 raw files then the virtual copies. Yet the original image shows no clipping in this area.

Some other points worth mentioning:

  • On the left the ocean is crisp and detailed since one image was used. On the right the water is milky since it was blended from 7 images which by the way all seven shots were taken in about 1 second.

  • The contrast is greater on the image on the left.

  • The detail in the clouds (except for the blown section) is nearly identical.

In conclusion: I have to acquiesce in that prior to this I would have defined a pseudo HDR as: Taking a single .JPG or .TIF (ie. not containing any additional data like a RAW file) and then processing thru exposure blending or tone-mapping. Now I have to include the processing of a single .NEF in that mix for sure, based on the results shown here.

So I believe my new rules on HDR to be this:

  1. If the DR range in a scene is less than 3 to 5 stops and there are moving subjects processing a single .NEF will work just fine and probably produce a more appealing image than a bracketed shot.

  2. If the DR of the scene is greater than 3 or 5 stops and the scene contains no moving subjects, shooting a bracketed shot is the way to go.

  3. If the DR of the scene is greater than 3 or 5 stops and the scene does contain moving subjects like the example here, shoot it bracketed and then make a creative decision in post to layer mask in a single frame, like the water which is easy to do.

Thoughts?
--
Chris
http://www.33g.com/photos

The difference between a successful person and others is not a lack of strength, not a lack of knowledge, but rather a lack of will.

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