# HDR vs. Tone-mapping... do I have this right?



## manaheim

Ok, so doing a bit of research to understand the "difference" between tone-mapping and HDR...

What I've come up with is that HDR is high dynamic range... we know this, however, I think the key bit is that the word "high" is relative.  In theory, any of the images that we produce that have a higher dynamic range than what is possible to capture with a single exposure, could be called "high dynamic range", but then could also be easily argued as one person's "high" may be higher than another's.  In the end, I think that this is a descriptive and subjective term, but it arguably applies to any image that would display more detail and tones than would be normally possible with a single exposure.

Tone mapping, on the other hand, is a process... a process "which transforms the image into a low dynamic range image suitable for viewing on a monitor" (source: Wikipedia)  This is an interesting perspective, because we understand monitors and cameras to have a limited dynamic range (thus implying LOW dynamic range), and yet the images that we generate via the Tone Mapping process are usually the images that we parade around as "HDRs".

So, in short... we use a tone mapping process to generate low dynamic range images such that they can be displayed on a monitor, but that have a higher dynamic range than would be possible to capture with a single exposure from a camera.


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## manaheim

You have all been clearly stunned into silence by my poignant analysis.


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## c.cloudwalker

:addpics:


Just because I don't know what else to tell you.


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## Jon_Are

My view of HDR is that it is a technique of overcoming the inherent limitations of the camera (and display screen), which will likely never approach true realism. I can't imagine that any future technology will be able to duplicate what the human eye (and sensory/neurologic capabilities) are able to produce.

I've shown some of my HDR stuff to people, and they often say, "wow, it looks like you're right there." Well, no, it really doesn't. It may be different than most photographs you've seen, but it falls far short of what the human eye sees. Even if you nail the colors and the exposure, there is a spatial element that the two-dimensional screen/print lacks. This is why those gimmicky Hollywood 3D movies are, when the studios spout how realistic they are, laughable.  

As for tone mapping, your last sentence pretty much sums it up. We spend all the time and effort to pretty it up, then we have to turn around and 'dumb it down' to the point where the screen can display it. 

Everything is a compromise.

Everything.

Jon


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## musicaleCA

I pretty much agree with you manaheim. The thing to note though, is that the tone-mapped image is just a boring ol' normal dynamic range image. What we're doing is trying to make some use of the details that are captured by the HDR process. We can't do that in the most preferable way (just leaving them at the luminosity they are and displaying them as such, because that falls waaaaaaay outside any device's abilities), so we bump up the shadows and bring down the highlights; basicly squish the HDR data into a normal 8-bit image.

This will change once some brilliant scientist figures out how in the heck to create print media that has a high dynamic range that compliments these images we're creating. In all things right now in photography, it's really the display technology that's lagging behind. Very far behind...


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## c.cloudwalker

musicaleCA said:


> This will change once some brilliant scientist figures out how in the heck to create print media that has a high dynamic range that compliments these images we're creating. In all things right now in photography, it's really the display technology that's lagging behind. Very far behind...



Not sure I get this at all. Ansel Adams (just to use an extreme example) had not problem getting a high dynamic range in his prints. If digital cannot achieve this than maybe we need to take a step back and wait for digital technology to catch up.

As for the display technology, are you talking about computer monitors? If yes, photography was not really intended to be viewed on a monitor. This technology is great for sharing photos (snapshots) with friends but to see the work of good photographers you have to be willing to make the trip to either the gallery or the magazine rack. IMHO, the monitor is about the equivalent of the newspaper as far as quality is concerned.

This reminds me of reading about Bill Gate's house where all the art was actually displayed on monitors. Ok, this guy wants to be Mr. technology but it made me wonder if he had ever walked into a museum.

Ask yourself this: if you see a painting in a book or on the internet, can you really say that you've seen the painting? IMO, no. Seeing the real thing is quite a different experience. And I don't see it being any different with photography.


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## Dwig

c.cloudwalker said:


> [...Ansel Adams (just to use an extreme example) had not problem getting a high dynamic range in his prints. ...



False, in terms of the range common in true HDR images, dear old Ansel never came close. True, his best prints achieved a dynamic range a little better than the best of today's digital prints, the difference isn't all that much when compared to the range possible in a 48bit/pixel HDR image.

Ansel employed a very carefully controlled scientific process to tone map the scene onto the negative and then to map that onto a print. The toe and knee of the D-LogE curve (AKA H&D Curve, a term I prefer as is honors the original scientists) were used to compress highlight and shadow detail. Additionally, printing techniques (dodging, burning in, uneven chemical treatment, ...) were used to accomplish the tasks done electronically with tone mapping. The final prints, while beautiful, don't have that much more range, black to white, than the best of today's digital prints.


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## musicaleCA

Indeed. And cloudwalker: When I say display tech, in this case, I mean every medium, from paper to screen. All of it lags behind significantly. Heck, we don't even have monitors that can fully display the entire AdobeRGB range of colours (maybe Garbz will correct me if I'm wrong, but all I've ever seen are 12-bit monitors at the widest end in terms of gamut), let alone ProPhotoRGB, let alone the visual spectrum.

Hmm, this is another reason I keep my RAWs. Right now, I'm editing on paltry displays. Perhaps somewhere down the line things will improve greatly, in which case, it'll be nice to backtrack on my best images and re-edit them to suit better display media.


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## Wyjid

manaheim said:


> Ok, so doing a bit of research to understand the "difference" between tone-mapping and HDR...
> 
> What I've come up with is that HDR is high dynamic range... we know this, however, I think the key bit is that the word "high" is relative. In theory, any of the images that we produce that have a higher dynamic range than what is possible to capture with a single exposure, could be called "high dynamic range", but then could also be easily argued as one person's "high" may be higher than another's. In the end, I think that this is a descriptive and subjective term, but it arguably applies to any image that would display more detail and tones than would be normally possible with a single exposure.
> 
> Tone mapping, on the other hand, is a process... a process "which transforms the image into a low dynamic range image suitable for viewing on a monitor" (source: Wikipedia) This is an interesting perspective, because we understand monitors and cameras to have a limited dynamic range (thus implying LOW dynamic range), and yet the images that we generate via the Tone Mapping process are usually the images that we parade around as "HDRs".
> 
> So, in short... we use a tone mapping process to generate low dynamic range images such that they can be displayed on a monitor, but that have a higher dynamic range than would be possible to capture with a single exposure from a camera.


 

it's a matter of compression. i've found very few instances when you really need to shoot multiple exposures to capture the detail in a scene. again the display is the issue. rarely are highlights completelt blown and shadows completely black. if you play with the image long enough, much of the detail can be brought out. unfortunately the image quality begins to suffer. in most cases HDR techniques are not necessary so much to capture more of the detail, but rather to preserve the quality of the detail in the shadows and higlights. wether it's a tone mapped standalong exposure or a compressed HDR image, the point is really to create an image that is visible in all parts. remember that our eye is the final processor. that being the case if an image displays detail from it's shadows right up to it's highlights and your eye doesn't notice anything missing... its range is as great as it needs to be. i think the potential for displaying images is great on a digital display. not right now... but eventually. the limitation of prints is that they are reflected light only, and reflect light at the same angle across the entire image. a display that is it's own light source is ultimately preferable for its capacity to create it's own light, and phisically control it's levels in a more locally adaptable manner. secondly, if we're considering how to create images that more accuractely represent reality, binocular vision also does a lot for detail. while each eye sees beautifully on it's own, it's when your brain combines to slightly different images, and interprets the data from both, that it sees into the scene and fills in the gaps seeing more than is actually captured by the sum data of both the eyes. this is a similar process to generating a composite HDR. so i put it to everyone out there, why not go that extra mile and start creating sterioscopic HDRs? detail in all tone ranges, and allowing the brain to create it's own interpretive detail as an added enhancement. i'd like to see what you come up with. i once tried making a stero image using to differently exposed JPGs and let your brain do the HDR processing, but i think it would be interesting to see to slightly different HDRs used in a stereo image. the effect could be interesting. they could be slightly offset and slightly different exposures to allow for the MAXIMUM amout of detail!


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