Hdr?

When trying to use HDR is it possible to adjust the same picture with a levels adjustment, save it as two different ones. One adjusted for the sky and one adjusted for the foreground and then merge the two. I have tried this and get the error message NOT ENOUGH DYNAMIC RANGE. What's the secrect to using this tool?
Greg

Nope, it's not possible for the HDR tool in Photoshop to merge the same photo, post processed multiple times. I don't know the technical reasons behind it, I just know that that's how it works.

I shoot RAW, and I have post processed the files multiple times, for the dark areas, and the light areas, and combined them in PS using masked layers, not HDR.

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Originally Posted by mjs1973

Nope, it's not possible for the HDR tool in Photoshop to merge the same photo, post processed multiple times. I don't know the technical reasons behind it, I just know that that's how it works.

I shoot RAW, and I have post processed the files multiple times, for the dark areas, and the light areas, and combined them in PS using masked layers, not HDR.

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It is not entirely true that you can't reprocess. The problem is that you have to strip all the EXIF data out of the file. The easiest way to this is to "Save For The Web" and then of course you are dealing with a JPEG-8 file which is terribly limited in range. If you have a utility to to 'clean APP/EXIF/IPTC' markers from a TIFF file, then you can reprocess BUT -

The original range of the sensor/image is still going to be the limiting factor.

Adobe Photoshop in the HDR filter tool looks for a difference in the shutter/aperture combination and if it doesn't see it won't process. The algorithm used will produce a weird image if it combines the same image twice (or won't work as you can't divide by zero).

The more images exposed over a 6-7 stop range work the best.

That's very interesting. I had never thought of deleting the EXIF data. Another way to remove the EXIF data is to open your image, then select the entire image, copy it, open a new plank image, paste your photo into the new image and then flatten it. Then you can save the file as whatever you want. I know it gets rid of the file info, but I'm not sure if it get rid of everthing that the HDR is looking at.

Thanks for the help. Next time out I guess I need to take a tripod....
Greg