CS2 Merge to HDRdiffernt outputs of same RAW file

[davelasker]

In MR's Merge to HDR First Look he says no, you can't use different outputs of the same RAW file. If you use Adobe Camera Raw to save a single raw file as multiple images with the exposure slider set to different values, and use Merge to HDR, you will get the dreaded error message There is not enough dynamic range in these photos to construct a useful HDR image.

Purely by accident I figured out how to solve this problem. I believe it is caused by Photoshop using the EXIF exposure meta-data as input to its algorithms. Since the multiple images saved from a single RAW file have the same exposure meta-data, Photoshop gets confused.

I had been experimenting with various other HDR methods as described here, here, and here to attempt to recover highlights from a raw image. In all of these methods I was using Russell Brown's Place-A-Matic script to place 2 copies of the same raw image as 2 layers in the same file. Although I didn't realize at the time, the good news is that this script also strips off all EXIF data.

I wasn't happy with the results I was getting using the above methods, so I decided to try Phtotshop's HDR, forgetting that it didn't work in this case. To do it, I saved my layers as individual psd files before using Merge to HDR. Since none of these files contain any exposure info, when I ran Merge to HDR on these files, I got this dialog:



I then lied and assigned each image the same relative EV to the others that I used when changing the ACR exposure slider in my layers. I don't think it matters what exposure values you enter, as long as their relative EV's are the same as the relative values of the ACR exposure slider you used when creating the individual files. Now, since Photoshop has correct relative exposure values for the images, Merge to HDR works fine.

I would assume any other method that either stripped off or modified the Exif exposure data would also allow Merge to HDR to work correctly.

Hope this helps someone...

Dave

[Blendenteufel]

Well, I think you are describing just another way of shifting image information from here to there and saving yourself the work of a luminosity mask and local contrast enhancement because it is applied at stage of converting into 16bit. There are several ways of achieving this, this one probably not the easiest of all.

But the real value of HDR lies in compressing a large dynamic range into 16bit. One single raw file does from my point of view not contain enough dynamic range to justify the effort...

I doubt there is much value on using HDR in this case, I prefer to utilize the full power of a raw converter (custom curves) to obtain as much detail from a single raw file as possible.

[oldcsar]

While I do agree that Luminosity mask/digital blending of two different raw conversions produces acceptable and easy results, I think it's great that you've experimented and found a way of using HDR for multiple exposures from a single raw file. It's likely that you wouldn't be able to achieve the great dynamic range you'd get from multiple bracketed raws, but this at least gives people a chance to use the tool with a single raw exposures... for some, it may yield better results than the digital blending technique found here:

http://www.luminous-landscape.com/tutorial...-blending.shtml

The problem is that I've heard from several people that the Merge to HDR is a challenging tool in regards to producing a pleasing result. I'll give this a shot, though.

[PeterLange]

Dave,

I’m glad that you raised this subject, because I could imagine that more people (like me) are interested in such kind of “poor man’s HDR” resulting from one single Raw file.

After knowing at least some of the procedures which you’ve quoted above, my current approach is:
/> to get a “linear” conversion from ACR by setting Brightness & Contrast to zero (curve tab linear w/CS2).
/> Then in Photoshop to add a Curves’ adjustment layer + Contrast mask

With this or other related procedures, the core challenge seems to be:  to work out a good contrast mask.  Unlike some examples in literature, many real-world scenes tend to require more effort e.g. than just to apply a plain b/w gradient to mask the bright sky, etc….

So if the PS Merge to HDR function can contribute here, it could be worth the effort.  I’ll definitively give it a try.  In the long run (sooner or later), I’d personally have the hope that such a tool for contrast-masking/”HDR”/highlights-protection becomes part of ACR
(respective feature request was already placed).

Anyway, thanks a lot for sharing your insights!

Peter

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