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07-13-2009, 10:54 AM   #1
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DRE in K20

I used the Dynamic Range Expansion feature of my K20 (as described on page 79 of the manual) and was greatly disappointed. I took two pictures -- one with the feature turned on, and one with it off -- of my neighbor’s house across the street, which is gray brick, with a white garage door. All that happened was the image taken with DRE on had less contrast -- I duplicated that image by reducing the contrast of the “DRE off” shot one click in the Quick Color Tuning program of PhotoImpact. So, what’s the advantage of this “feature?”

07-13-2009, 12:16 PM   #2
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the advantage, if you shoot jpegs like me, is that if you have with this feature (similar one exists on the K2) is you can protect much more of the shadow detail (if it exists) than with a normal setting, even with contrast set to low.

I tested it on my K7 and found that for an image of a flower on green leaves, it did not change the greyscale value of the flower I was focused on, but the dark green leaves in the background had the greyscale lifted from about 15 to 35. This is about 1/2 a stop, and means that the things in the shadows carry a lot more image detail than they used to. BUT you have to want to use this data.


If you like the contrast as it is, I doubt this is for you, but if you are out shooting and want more details in the shadow when part of the subject is exposed for sunlight, this will help.

Knowing what it does and the range of adjustment it makes to an image goes a long way in knowing when to use it or not.
07-13-2009, 01:45 PM   #3
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QuoteOriginally posted by Tom Lee Quote
[FONT="Arial"]I used the Dynamic Range Expansion feature of my K20 (as described on page 79 of the manual) and was greatly disappointed. I took two pictures -- one with the feature turned on, and one with it off -- of my neighbor’s house across the street, which is gray brick, with a white garage door. All that happened was the image taken with DRE on had less contrast
All that happened, or all that was *obvious*? Of course one effect of extending the dynamic range will be to reduce contrats - that's indeed the whole point. The idea is to make there be less less difference between what would otherwise have registered as pure white and pure black, so that more room can be created for brighter and/or darker values. But simply reducing contrast won't give you those brighter brights or darker darks - all it will do is reduce the difference between white and black.

Unless your subject was shot in bright sunlight with deep shadows, it wasn't the kind of scene that would have benefited from D-range. But try again with the sun shining directly on the white door, and make sure you've got something dark and in shadow in the picture too. You'll find with D-range, either the door or the dark shadowed object will have clipped - it will have been rendered without detail. With D-range, there's a chance that you'll have some detail in both. Of course, it might also be just too extreme a situation. But there are *some* situations where it works like this. And shooting normally then reducing contrast won't help bring back the clipped detail.

On the other hand, shooting RAW, exposing to avoid clipping a the right end, then using curves in PP to bring up the shadows - that will indeed do exactly what D-range does for JPEG.
07-13-2009, 02:49 PM   #4
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If you want to see where EDR shines, do a test with some bright highlights on a white subject with some texture. Say a white-petalled flower like a daisy. Or a shiny yellow buttercup will do. Then take a look at the histograms of the non-EDR and the EDR shot. There will be at least a clear one stop improvement in highlight headroom with the EDR on. Which means you have that much more room to play with the highlight end of the range. EDR allows you a little more room for error in the highlights. Nothing more, nothing less. Some complain that this occurs at the expense of deep shadow noise. This may be true. But those wishing to preserve highlights may not care too much about shadow detail.

07-13-2009, 03:47 PM   #5
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QuoteOriginally posted by jbinpg Quote
If you want to see where EDR shines, do a test with some bright highlights on a white subject with some texture. Say a white-petalled flower like a daisy. Or a shiny yellow buttercup will do. Then take a look at the histograms of the non-EDR and the EDR shot. There will be at least a clear one stop improvement in highlight headroom with the EDR on. Which means you have that much more room to play with the highlight end of the range. EDR allows you a little more room for error in the highlights. Nothing more, nothing less. Some complain that this occurs at the expense of deep shadow noise. This may be true. But those wishing to preserve highlights may not care too much about shadow detail.
I went the other way and took a shot of something "normal" with deep shadow, as reported above, the "normal part had the same illumination but the deep shadow was at least a stop lighter, hence the details within the shadow are much better preserved and identifyable.

I think it is another tool in my JPEG bag of tricks to keep me from shooting raw.

As long as you think your way through all the adjustments, there is no need to post process.

and before that argument starts, I read an article in Popular Photography about fixing photos, and step 3 was to reduce the image to 8 bit color depth. It appears that the recommended workflow is only WB and exposure at full depth. all other fixes are done in 8 bit. so again, I find myself questioning the whole point behind RAW. Sorry for hijacking the thread.
07-13-2009, 04:01 PM   #6
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Thanks, everyone

I appreciate the explanations. My thinking was headed in the right direction -- there are times to use DRE, and times it won't be of much help -- but your explanations made it clearer for me when those times are. This is an excellent forum, with great people!
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