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11-07-2006, 06:29 PM   #1
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HDR and ISO bracketimg

Hi,

If I am way out in left field on this please yell at me. Dynamic range of digital cameras has always been one of their greatest weaknesses. The Sony sensor in the K10D is capable of about 8 stops of DR. By using 3 or 4 files shot at different shutter speeds and blending them together you can kick this up to 10 or 11 stops. That is about as much as todays printers can handle so there is very little sense in going beyond that.
The major problem with that is if there is any movement between shots you can't get a sharp print. The time lag between exposures also makes hand held shots impractical. What if you could bracket with ISO? ISO 100 for the shadows, 200 for mid tones and 400 for the highlights. All 3 shots would be produced with one exposure and processed for ISO in the camera. I know the K10D can't do this, but if it could would it work?

Regards,
Ken

11-07-2006, 07:28 PM   #2
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No, it wouldn't work. Only one exposure would be made, and whatever postprocessing is applied (here the ISO gain-up) will not change the dynamic range.

Your best bet is to shoot raw and expose so that the highlights burn out just a little bit (which you can recover in the raw processor).
11-07-2006, 07:51 PM   #3
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Ole,
Thanks for your reply. Let me ask you this. If I take one exposure at ISO 100 and then take another exposure at ISO 400 and blend them together would I increase DR as I would if I did it with a 2 stop differance in shutter speed?
Thanks,
Ken
11-07-2006, 10:01 PM   #4
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QuoteOriginally posted by regken Quote
Ole,
Thanks for your reply. Let me ask you this. If I take one exposure at ISO 100 and then take another exposure at ISO 400 and blend them together would I increase DR as I would if I did it with a 2 stop differance in shutter speed?
Thanks,
Ken
No you would not. The dynamic range will be the same. The ISO 400 picture would just be more grainy (noisier).

Keep the ISO and change the shutter speed - that will do the trick (for a static subject!).

When I need more range I do as follows: I take just one shot, in RAW. Then I convert it twice, first with as much highlight detail as I can get, then with as much shadow detail as I can get (washing out the highlight). I then blend this two pics in Photoshop masking appropriately. The resulting dynamic range is compressed of course, but I do get more shadow detail than would otherwise be possible.

11-07-2006, 10:06 PM   #5
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HDR Solutions

I've read some interesting articles about PS HDR techniques, but am no expert at any of them. I find that it is better to be slightly underexposed and use PS to mask and bring up the areas in need. If highlights are blown, I've had very little success in restoring them. If you want to learn the best techniques I suggest you go to DPReview, Retouching Forum. There are some real experts over there and they seem to love to help. Good luck.
11-08-2006, 05:52 AM   #6
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HDR is supposted to work something like this:

you take the same shot at different times of the day, then HDR stacks them together and gives it more dynamic range.
Of course if the shots started bright and then ther was falling light, you would not have to wait to long between shots.

just my take on this
11-08-2006, 07:50 AM   #7
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I haven't done this, but my understanding is that one can 'develop' HDR using a single RAW file. This would make taking multiple jpg exposures unnecessary.

Also, based on my understanding, the best way to do the multiple exposure thing is to bracket shutter speed only: leave the aperture and ISO constant so you don't get DOF artifacts.

But then, the only time I've tried HDR was to mis-use it
11-08-2006, 09:25 AM   #8
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I didn't give an accurate answer

here is a link that does Photoshop CS2 HDR

cheers

11-09-2006, 02:33 PM   #9
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I don't understand why it wouldn't work.
If I take one shot that is set to a longer exposure to get detail in the shadows,
then I'll blow out on the brighter areas.
Next I change only the shutter, to a couple stops shorter, keeping ISO constant. I'll have less blow out, ideally none.
Then, I don't know photoshop, but surely you can substitute sections from the
less exposed shot into the blown out areas of the more exposed shot and
you have yourself a compressed dynamic range image with details in a wider range of light. Albiet - this may look contrived and unnatural.
11-09-2006, 04:33 PM   #10
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QuoteOriginally posted by leaton Quote
I don't understand why it wouldn't work.
If I take one shot that is set to a longer exposure to get detail in the shadows,
then I'll blow out on the brighter areas.
Next I change only the shutter, to a couple stops shorter, keeping ISO constant. I'll have less blow out, ideally none.
Then, I don't know photoshop, but surely you can substitute sections from the
less exposed shot into the blown out areas of the more exposed shot and
you have yourself a compressed dynamic range image with details in a wider range of light. Albiet - this may look contrived and unnatural.
That approach will work.
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