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Old Feb 14, 2010, 12:40 PM   #21
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Martin, I d/l and tried out your program - nice job, and such a small file - now if you could just code it for a PS plugin ......

I have been doing some HDRs for quite a while with Photoimpact, and have tried out a couple other programs for this. I try to keep my results looking somewhat realistic, and have found that the biggest benefit of using multi-stop exposures is the reduction in noise and increase in detail of the shadow areas - something that cannot be acheived with pseudo hdr. As I mentioned in my previous post, this has more significance with small sensor digicams than larger DSLR cameras. If the EV range is large enough, though, the larger sensor cameras benefit also.
The question for a lot of people seems to be "How far should I go?", and that is pretty much up to the individual.
Martin, have you looked at the program Image Analyzer? It has a routine to increase local contrast using a variable radius, with adjustable contrast and other variables. Pretty interesting, and may give you some more ideas - if you need any.

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Old Feb 14, 2010, 2:12 PM   #22
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Originally Posted by simple View Post
your never going to create a true hdr image from one file even by stepping the values if it was that easy even the pros would do it.
Some of them do. But I agree, three seperate exposures is probably better. But better is not necessarily a "qualitative" term.

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image ,,, how long would it take you in photoshop to create something like this http://www.facebook.com/album.php?ai...id=44511593477 the reason i post this link is because it is another example of hdr and those results are what i aim for one day
I have no idea. The page has a whole bunch of images - Which one are you talking about? Some of the images are garish to the point of being pure "Art," and have little to do with photography.

Hey, I LIKE Art! So what?



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i also downloaded your image but it is unworkable for some reason ?
I just downloaded it. Works fine. It's an Adobe DNG file, and if your program doesn't read DNG files it will be useless.

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Old Feb 14, 2010, 2:24 PM   #23
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Having played with the maths behind this in some detail for a couple of weeks, I think it depends on what you are trying to achieve, the scene you are trying to achieve it on and those both then dictate what source files you therefore need.

Essentially for any program, the maths takes a histogram for an 'area' of the original scene and equalizes it to give a full range. That's it - nothing cleverer than that.

The hard part is defining an 'area' for comparison. My interpretation of Photomatix results is that it's using something relatively simple such as a circular area which should be fast but gives halos which sometimes need to be corrected. I guess using layers in Photoshop involves some *potentially* complex masking to use different parts of each image. My program is creating those masks with some sophisticated fuzzy edge analysis but that makes it slow.

Anyway, different situations:

1/ In a scene where each element of the scene contains a range of tones from black to white then there is very little to do and a single JPEG can be good enough (for screen display anyway). You won't see much difference except some local sharpening. The dynamic range of the image can't be more than the dynamic range of the scene and some scenes just aren't dynamic in that way.

2/ In a scene where each element doesn't contain a full range of tones (so some parts are under exposed and some over exposed) but nothing is actually clipped then even with a jpeg you can equalise this pretty well but a RAW will obviously contain more levels so should give better, smoother results. This is pseudo-HDR.

3/ In a scene where some elements are so dark that they are clipped to black or blown to white by the range of a single sensor then you can only extend this range with multiple exposures. This gives some amazing looking results but can look surreal as Chatto says if you extend the range beyond what the eye would have naturally resolved. It's giving you a 'super-vision' version of the scene. This is true-HDR.

Just my interpretation. I think the mistake a lot of software is making is that it's trying to simulate what the eye does and forgetting the other half of the story which is what the brain does.
Interesting post. And to be truthful, I don't really know how Photomatrix works. Some things I Do know is that the real enemy of sharpening (i.e. the increase detail shown by Photomatrix) is chroma noise. I learned this a while ago, and therefore run a program like Noise Ninja Twice. Once to get rid of the Chroma, and then After sharpening, run it again to get rid of luminence noise.

I speculate that Photomatrix, gets rid of chroma noise and then increases the saturation, finally running a sharpening algorhytm (over the noise free areas of hyped color) to increase the detail.

Basically creating layers in Photoshop, using the same over and under exposed images, I can manually do the same things - Which in fact is what I did do.

If the scene is static enough, there's no reason the above can't be used with three seperate exposures and produce a "real" HDR image as opposed to my, err, pseudo images...

Dave
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Old Feb 14, 2010, 8:26 PM   #24
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Another, ahh, pseudo HDR by using the layers menu of Photoshop...

Full frame...



And a 100 percent Crop...

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