Hey Pro's I need help regarding HDR Photography using Single Image

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Originally Posted by Glenn NK

If one can get a reasonable result by combining two version of the same image (fake HDR), then it begs the question as to why not work with the single original image?

Comments anyone?

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It really just comes down to whatever is easiest. Sometimes you might need to apply a curve with a very steep and precise slope with the single file, whereas with two (or more) versions of the same RAW file you might be able to process each version for a specific area, and then combine them with layer masks. The actual information captured is the same, but the processing technique is very different.

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Originally Posted by Colin Southern

It really just comes down to whatever is easiest. Sometimes you might need to apply a curve with a very steep and precise slope with the single file, whereas with two (or more) versions of the same RAW file you might be able to process each version for a specific area, and then combine them with layer masks. The actual information captured is the same, but the processing technique is very different.

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Good points.

That one I posted of the duck was much easier the fake hdr way. The package I used does use layers and transparency but presents each image as a brightness graph and hides the layers from the user. Dark pixels on the left to bright on the right. Hard to explain but in the duck shot the graph just shows 2 straight lines of opposite angle a 45 degrees. At the height where these cross both images contribute equally to the final image. These line can be made into the usual curves etc with additional points so any mix is possible. If there are more than 2 shots the package may assigns curves to each one. In this case the process was a lot easier than trying to work on the whole shot. In fact by pre processing the 2 images is should be possible to remove the water entirely from one shot and the duck from another or variations on that. The differences are so great getting rid of the unwanted stuff should be easy. The author of the software also points out that accepting his automatic curve option and then working on the combined shot may well be the easiest and best option. That's fair enough really as most of the work was done with no effort or time at all. This is what the graph looks like and probably provides a better explanation than I have.


http://i50.tinypic.com/123rvb5.jpg

John

When I see these discussions that dispute the definition of a photography term, I hope to remember in the future to refer to dpbestflow.org, which is an American Society of Media Photographers initiative funded by the U.S. Library of Congress. Their definition of HDRI is as follows:

High Dynamic Range Imaging (HDRI) is an imaging technology developed to capture the entire range of light present in a scene. HDRI can far surpass the dynamic range restrictions of traditional chemical and digital photography, and can more accurately be used to recreate a scene in terms of how human vision works. Specialized software (tone mapping operators or TMOs) is used to compress the greater tonal range of HDR images into a tonal range that can be displayed on conventional monitors or printed.

Shooting HDR scenes with conventional digital cameras requires photographing a sequence of exposure-bracketed Low Dynamic Range (LDR) captures, and then using specialized software to merge them into a single HDR file. The HDR file is then “tone mapped” back into an LDR image that can be displayed and printed. These tone mapping applications, called Tone Mapping Operators (TMOs), can be stand-alone programs or plug-ins within another application such as Photoshop or Aperture.

Notice that by that definition, many of the purported techniques discussed in this thread to be HDRI in fact are not. To read the entire related piece, click here.

I often wonder if that definition is dated. Let's say a raw file has 10 usable stops captured into it. Not that unusual these days. A camera will use a low slope S curve to get that into one of it's jpg's. The low slope means contrast is reduced and the ends of the s compress the high and low ends even further. One of mine can gets more like 11 in.

There are several ways either type of image can be processed to produce something that looks natural over the entire tonal range on a screen. Colin has reckoned that a screen has 5 stops available. Me on the basis of 8 bits being the 1st stop and the possibility of see a 1/2 stop reckon it can be 6 stops. Which ever the images finishes up with 10 stops compressed into a much smaller tonal range and looking natural. If that's not HDR what is?

:) Yeh, I suppose some could argue about 10 stops but not something that starts off at significantly more than 5 or 6.

With fake HDR as I called it a raw file is being processed to produce 2 images where the luminosity of the bright and dark areas are being moved into the screens luminosity range so that they can be clearly seen. At the same time a curve is being used to make the contrast natural in those regions. HDR??? or not.

Search fake HDR lately and software that is intended to make single images look HDR like especially colour wise is likely to come up. Colour style needn't have anything to do with it. Curious really because tone mapping needn't have been involved in producing a true HDR image even from several exposures. The only mapping needed is the curve used to process the file which oddly enough is tone mapping as that also modifies contrast on the basis of the contrast that is already there.

The other point of course is that tone mapping is used every time some one processes a raw file. One tone is a mapped to another.

John
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Originally Posted by ajohnw

Colin has reckoned that a screen has 5 stops available.

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No - I always say 4 for a print and around 6 for a monitor. If you've seen me say 5 somewhere then it's probably just a typo.

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With fake HDR as I called it

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I wouldn't even call it "fake HDR" at that implies HDR is a "look" whereas in reality its a technique. An HDR image - well executed - may well not look any different to any other image. How many would call this an HDR image (which it most certainly is)?

http://www.pbase.com/cjsouthern/imag...9/original.jpg

How many might call this an HDR image (which it most certainly isn't)?

http://backup.cambridgeincolour.com/...7/original.jpg

Personally, I prefer the term "ultra tone mapped" for "those" kinds of images, although I'm open to a better term (I've heard a few that are more accurate, but I can't can't repeat them!).

I had that shot of your parents place in mind when I mentioned HDR needn't look ultra tone mapped. 9 shots if I remember correctly.

Not up to your standards yet Colin but this one is HDR 2 from raw which I think is a better way of describing that. I couldn't get the clouds correct without it. Believe it or not it's very representative.

http://i61.tinypic.com/29wx405.jpg

And this is a fake HDR of it so it's a bit of both. Bit over done really but the grass was wet. Just like many others nothing like reality even though I toned the effect down rather a lot. Might be useful for a print I suppose. So far I haven't managed to get the flat colouring PS gives out of the box. :D Maybe that's fortunate.

http://i57.tinypic.com/9u6lg6.jpg

I read a mathematical argument that once gama is applied to a screen it looses a stop so 8 is impossible. Then comes the leak through of the back light which more or less looses another.

John
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Originally Posted by ajohnw

I had that shot of your parents place in mind when I mentioned HDR needn't look ultra tone mapped. 9 shots if I remember correctly.

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No - just 5.