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DPChallenge Forums >> Photography Discussion >> What is it about HDR?
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 11/13/2006 01:11:49 AM · #1
I have a very basic understanding of HDR. I didn't enter the challenge...not enough time. I'm curious why HDR pictures (that are done well) have an almost fake/cartoonish look to them? If there's anyone out there that really understands how it works, I would appreciate some sort of posted tutorial/explanation (when whoever it is gets some time). I think it's a very cool tool, but without a good explanation, it's relatively worthless. I've looked online, but I haven't found a good tutorial. Based on the submitted HDR images that I saw, there are at least a few people that really know how to do it. Thanks in advance.
 11/13/2006 01:15:42 AM · #2
HDR can really add c a crisp look to a photo but unfortunately most people over use it to cause unnatural colors and contrast that is way to high to be anything other than art work. I feel the key to photographic HDR is to still have the photo look like the photo, forget the purple, pink skies and vivis light green grass and trees. The sharpness and saturation while maintaining the look of the actual scene is critical to not look like a cartoon as stated.
 11/13/2006 01:18:07 AM · #3
Well, like with everything else HDR/Tone Mapping can be used for artistic purposes (i.e. the cartoon look) and just for correction (i.e. realistic look). In other words, it doesn't have to look cartoony.


Message edited by author 2006-11-13 01:20:32.
 11/13/2006 01:22:00 AM · #4
HDR would mean high dynamic range in the photo. Details in both very dark and very bright areas (preferably).
 11/13/2006 01:33:02 AM · #5
There are times when HDR may be able to help some specific images. Since we all view our images at the mercy of low screen resolution, we are not apt to gain much. When used basically to correct tonal gradation or faithful reproduction it serves a better purpose.

You climb the big mountain of 32bit and here you mix and stir and then it is time to bring it out down to our screen's resolution and something happens. Many have a plastic look with coloration found nowhere in nature and many images play with different overlays, well, it goes on.

Again, it is a great advancement but it takes a discerning eye to avoid visual abortions.
 11/13/2006 03:01:37 PM · #6
I'll throw up a "trial balloon" and ask you all to comment:

We see the world with a wide dynamic range and set of colors. Painters and other artists have a more limited set of pigments, and so have compressed the dynamic range and set of colors they use. That is, they have mapped the world's colors to the colors their paints, pencils, etc support. Or at least some of them have.

IMO, some HDR photos look unrealistic, more like paintings or other works of art than photos. Also IMO, this is a valid style of photography, even though its not photojournalism :-)

Up till now, most photographs used a limited set of the worlds colors and dynamic range, and there was a more or less 1:1 mapping.

HDR allows us to compress dynamic range (which includes the set of colors) into a set the printer and display can reproduce. When this is all that is done, and it is done in a more or less linear manner, we get a photo that shows details in highlights and shadows, but looks very low-contrast.

HDR programs often allow a sort of "local contrast enhancement". If you have a picture of someone in a white shirt and dark blue jacket, in real life the highlights on the jacket will be darker than the shadows on the shirt. But in an HDR photo with a lot of local contrast enhancement, the highlights on the jacket will print in a lighter tone than the shadows on the shirt. See //web.mit.edu/persci/people/adelson/checkershadow_illusion.html for an example. More are located at: //web.mit.edu/persci/gaz/


Message edited by author 2006-11-13 15:04:29.
 11/13/2006 03:17:11 PM · #7
Without HDRI, basically the only way to compress the tonal range of an image is to make it less contrasty, which robs it of details, sharpness, and luminance. The more contrasty your original scene, the more of a problem this is.

With HDRI and tone mapping, you can flatten the image AND add local contrast/luminance back to it with tone mapping. The tendency of people who are new to the tool is to produce extremely flat images with extremely contrasty details, and while this is an interesting "look" it's not really what HDRI/tone mapping is designed to do.

On the other end of the spectrum from this hyper-flattening effect is stuff like this:

original

tone mapped

This isn't even really HDRI, because the single image itself was not out-of-gamut anywhere. Instead, tone mapping has been applied to a "dull" image to INCREASE the contrast and luminance. If you look closely between the two, you'll see, for example, that all the light areas in the sand are actually there in the original, they are just much less pronounced. Ditto the darker areas in the sky. So this image is all about altering LOCAL contrast to render a more luminous image, one which is MUCH closer to what My eye saw than the original, straight-from-RAW image.

Now of course, THAT image could have been processed into a nice version by more conventional means, and even in theory made to duplicate the tone-mapped version by very complicated dodging, burning, and local levels adjustments.

So basically, "true" HDRI imaging involves first making a composite of several exposures (fundamentally, one for the mid tones, one for the shadows, one for the highlights, but many more may be used as needed). This produces a VERY blocked-up rendering at both the dark and the bright ends of the histogram, and then you tone map that to compress all this information into the range you can reproduce on the screen (or in the print). The rest of tone mapping, once you have the compression set, is adjusting the relationship of the different image areas to each other, and this is where you can go way overboard if you feel so inclined.

R.
 11/14/2006 05:40:13 PM · #8
haven't seen this link the forest of HDR threads. Thought it might be of interest. It shows some of the less obvious, non-intuitive ways to do tone mapping in CS2, that is hidden under the Image->8 bits menu option,
rather than in the HDR dialogs

Photomatix versus Photoshop CS2

If you listen to some of the chatter on the internet about the HDR Processing capabilities of Photomatix versus Photoshop CS2, you may be led to believe that Photomatix is far superior. My research and experimentation disproves this premise to my satisfaction. Beginning with the same three source images, and following the suggested workflow for each program, and then applying very similar final global adjustments in Photoshop -- increased saturation and added S-Curve -- I was able to achieve very similar results.

11/14/2006 06:55:11 PM · #9
Photomatix can be bought at a savings of 70% if you are a student.
 11/14/2006 07:38:52 PM · #10
Originally posted by PhantomEWO:
Photomatix can be bought at a savings of 70% if you are a student.


Or if you teach.
 11/15/2006 11:37:46 AM · #11
Originally posted by Bear_Music:
Now of course, THAT image could have been processed into a nice version by more conventional means, and even in theory made to duplicate the tone-mapped version by very complicated dodging, burning, and local levels adjustments.

Hi Robert,

Have you tried USM to increase local contrast? Start out with a width of 200, 60% and the last parameter (I forget what its called) set to about 3 or whatever works to reduce the effect of noise. Then you can do a couple of other layers with different settings.

11/15/2006 11:42:22 AM · #12
Originally posted by hankk:
Originally posted by Bear_Music:
Now of course, THAT image could have been processed into a nice version by more conventional means, and even in theory made to duplicate the tone-mapped version by very complicated dodging, burning, and local levels adjustments.

Hi Robert,

Have you tried USM to increase local contrast? Start out with a width of 200, 60% and the last parameter (I forget what its called) set to about 3 or whatever works to reduce the effect of noise. Then you can do a couple of other layers with different settings.


Sure! I actually have an action I created for this.

R.
 11/22/2006 05:18:20 PM · #13
Ill stick with photoshop, thank you. Ive heard the HDR term for years now with my photos. People claim my photos are HDR, but Ive never touched photomatrix untill the past 2 weeks and Im not getting better results with it. Practice? perhaps, but Im not much of a major editing guy. Or an HDR fan .
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