# HDR... shouldn't it be done using ISO bracketing?



## Iron Flatline (Jun 20, 2008)

Soooo.... just sitting on a plane, and I've already finished my magazine.

I was musing, and thought the following: if ISO is a measurement of light sensitivity, wouldn't it make the most sense to ISO bracket for an HDR shot? Rather than exposure time?

I guess I can answer my own question... most ISO starts graining above 400, so a pristine print is better achieved with Tv bracketing than  ISO... but a good noiseless ISO system sure might work nicely...


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## Rogan (Jun 20, 2008)

Only one way to find out


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## tirediron (Jun 20, 2008)

Ideally, your exposure changes for an HDR should be made using shutter speed unless subject or camera movement make it impractical, and the reason is that both apeture and ISO have a potential visual impact on the image, ISO as Fe- mentioned by dint of noise, and apeture through DoF.  

From a practical viewpoint, with low ISOs, medium and above shutter speeds, and subjects distant enough to give substantial DoF it likely won't matter much which you use, presuming you shoot in a manual mode.


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## Arch (Jun 20, 2008)

Iron, previously i would have said don't bother trying, as you rightly pointed out about the noise issue... However, with the ISO range and relatively low noise some of the latest bodies have, it would sure be an interesting experiment.


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## JerryPH (Jun 20, 2008)

SS seems to be the best option.  As you said, ISO injects noise.  Aperture injects DOF differences.  SS is the one that least "changes" the end result but accomplishes the goal... severeal pictures of varying levels of exposure.


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## Garbz (Jun 20, 2008)

The other obvious problem here is that some of the extreme HDRs are made with 7 exposures. That covers ISO100 to ISO6400 and makes it impractical for all but D3 owners.


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## ChickenFriedRyce (Jun 23, 2008)

But doesn't HDR reduce noise when you process them?


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## Alpha (Jun 23, 2008)

ChickenFriedRyce said:


> But doesn't HDR reduce noise when you process them?



Unfortunately, yes.


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## Fiendish Astronaut (Jun 23, 2008)

Also I wonder if an HDR program like Photomatix would recognise the settings. I think it looks for shutter times - although I could be mistaken. You could always edit the data though but bit of a pain unless the results are radically different... but I can't see why they would be.


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## Alpha (Jun 23, 2008)

Does PM not allow you to manually enter shot settings? I know the PS HDR function does.


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## Fiendish Astronaut (Jun 23, 2008)

Alpha said:


> Does PM not allow you to manually enter shot settings? I know the PS HDR function does.



I don't think it does - or at least I haven't seen that facility when I've used it. Some would also argue that Photoshop doesn't really do HDR properly. I'm not sure about that, but Photomatix can certianly give much more dramatic effects that PS from what I've seen.


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## Garbz (Jun 24, 2008)

I think NR is done during the process but suppose your final picture is governed mostly by shadows. Everything that originally was dark in the standard exposure is now blanketed with noise, and everything that was original bright is now crystal clear. This would look very ugly having an uneven noise distribution in an image.

PM doesn't need manual entry as far as I know. I believe just ticking attempt to reverse engineer the tone curve takes care of that for you. Though I may be wrong about this. I have a HDR to do tomorrow anyway so I'll see what happens if I hose the EXIF data before I do it.

Photoshop does do HDR properly, and there is nothing to it really. What is done differently is the tonemapping (the bit where the HDR is no longer a 32bit HDR file and gets reduced back to our standard 8/16bit files which we can actually use). Not only can photoshop make HDRs just fine, to a limited extent you can do a bit of editing directly in them.

The tonemapper in photoshop isn't as intuitive as photomatix's either, but identical results can be achieved if you know how to play with that curve tool.


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## Battou (Jun 24, 2008)

Alpha said:


> Does PM not allow you to manually enter shot settings? I know the PS HDR function does.



Yes it does


*EDIT*

Now that I think about it, you might need to damage or remove the exif first, if mamory serves me correctly the options come up when PM can't find the exposure information.


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