Single Exposure HDR?

[mangtarn]

So i was looking around on deviantart and saw this post Warmth by =IvanAndreevich on deviantART it looks absolutely amazing. in the description it said "Noise reduction + distortion correction + HDR techniques from a single jpeg exposure." any ideas how you can get an HDR from a single jpeg?

 

[cgipson1]

The most common way is to change the brightness level in a single photo, and save that as -1, -2 or +1, +2... and then run the saved set through the HDR process. Keep in mind, that you are just maximizing the detail that is present in the original photo... you are not actually gaining the extra detail that actual overs and unders would have had.

Also.. most HDR programs will allow running a single image through also.. mostly for tone mapping, rather than true exposure fusion. There are a lot of settings one can change when doing this... and you can achieve some really interesting effects.

Examples from a single image run through Photomatix using some of the presets they have

Original

Tone Enhancement

Compressor Enhancement

 

[mangtarn]

thank you for your reply.
it's sort of what i guessed it would be. I should definitely give that a try considering the results look quite nice. but i am sure that the normal 3 exposure HDRs look better than the one exposure HDR. maybe the guy only had one photo to work with for that one but he did a great job at it.

 

[Bynx]

You can tone map any file. You cant get an HDR image from less than two files.

 

[Compaq]

I'm not too steady on the definitions here, but if you can capture the entire dynamic range in one exposure, would that, then, be a high dynamic range image? It wouldn't be tone mapped, but tone mapping isn't a necessity for HDRI, yes? The way I've understood it thus far, is that HDR isn't a "verb". You can't "HDR" an image. You either captured the dynamic range with one exposure or you didn't. If you didn't, then multiple exposures can be merged in the appropriate software and you can tone map the merged result. This will then only be a reproduction of the dynamic range in the original scene, that one exposure wasn't able to capture. You're no longer working with the RAW information when you merge the exposures, and everything after that point will only be a reproduction of the dynamic range, from algorithms that your software is using.

Again, correct me if I'm wrong!

 

[480sparky]

HDR is the process of extending the limits of a given camera/sensor to record the dynamic range of a scene.

If the scene has 7 stops of range between the shadows and the highlights, and the camera/sensor can record 7 or more stops of dynamic range, then you don't need to do any HDR at all. The range will be captured provided the exposure is correct.

If, however, the scene has more range than what the camera/sensor can record, then you will end up with either totally black shadows (0:0:0), blown-out highlights (255:255:255), or both in a single image. No amount of post-processing is going to magically recreate any details in those areas that were not recorded. Any attempt to do so will result in noisy shadows and sickly gray highlights.

 

[SlickSalmon]

I'm not too steady on the definitions here, but if you can capture the entire dynamic range in one exposure, would that, then, be a high dynamic range image? It wouldn't be tone mapped, but tone mapping isn't a necessity for HDRI, yes? The way I've understood it thus far, is that HDR isn't a "verb". You can't "HDR" an image. You either captured the dynamic range with one exposure or you didn't. If you didn't, then multiple exposures can be merged in the appropriate software and you can tone map the merged result. This will then only be a reproduction of the dynamic range in the original scene, that one exposure wasn't able to capture. You're no longer working with the RAW information when you merge the exposures, and everything after that point will only be a reproduction of the dynamic range, from algorithms that your software is using.

Again, correct me if I'm wrong!

Good questions, and the answers are likely to produce some debate.

Can you capture a high dynamic range image with a single JPEG? Yes, if you use a graduated ND filter, as was used in the photos posted above. But that's not the sense in which the term "HDR" is generally used, at least not in this Forum. The posters here tend to refer to HDR as something accomplished with software, such as Photomatix.

Is "HDR" a verb? Technically, no. But, people tend to confuse tone-mapping with HDR. Tone-mapping is one of the steps in the HDR process. It can be applied to a single image or to multiple images. Its overuse leads to the cartoonish effects that are often criticized in this Forum.

Is everything after exposure merger only a reproduction of the dynamic range of the original scene from algorithms that your software is using? Yes. Technically, any image taken with a camera is just a reproduction of the dynamic range of the original. But HDR technique overtly adjusts that dynamic range, sometimes in disadvantageous ways.

 

[mistermonday]

I'm not too steady on the definitions here, but if you can capture the entire dynamic range in one exposure, would that, then, be a high dynamic range image? It wouldn't be tone mapped, but tone mapping isn't a necessity for HDRI, yes? The way I've understood it thus far, is that HDR isn't a "verb". You can't "HDR" an image. You either captured the dynamic range with one exposure or you didn't. If you didn't, then multiple exposures can be merged in the appropriate software and you can tone map the merged result. This will then only be a reproduction of the dynamic range in the original scene, that one exposure wasn't able to capture. You're no longer working with the RAW information when you merge the exposures, and everything after that point will only be a reproduction of the dynamic range, from algorithms that your software is using.

Again, correct me if I'm wrong!

Compaq, you pretty well have it bang on. I would just like to expand on your comment about a merged file. When HDR s/w merges RAW files, which are usually 8 or 16 bits in depth, in order to accommodate the entire range of information, the source files are merged into a 32 bit linear image. These 32 bit images can not be properly displayed on out 8 bit monitors or printers so the Tone Mapping modules of the HDR s/w are used to remap the information into a n image that is visually pleasing in the 8 or 16 bit space. In the process of tone mapping, the software has the ability, typically through its Strength slider, to brighten the shadows/mid tone while darkening the highlights. This tonal inversion, when applied excessively, causes that overbaked, painterly, or unnatural, for example when a green pasture in the foreground is brighter than a blue sky) and it also results in rather strong halos.
The tone mapping modules of most HDR programs will allow us to apply the same adjustments to a single image. There, we are not actually increasing the dynamic range of the image but applying some tonal inversion, adjusting contrast at the global, local, and micro level, light gradients, and other conventional Low Dynamic Range adjustments like Brightness, Saturation, Temperature, Tint, etc.
Finally, given the proper HDR s/w, there is actually no value in making 3 exposures out of a single exposure and then merging and tone mapping. You will get better results from just tonemapping a single image and saving a lot of needless effort.
Regards, Murray

 

[Bynx]

You can tone map any file. You cant get an HDR image from less than two files.

When I made this statement it is assumed that if the whole range can be obtained in a single shot then it isnt really an HDR image. For example a shot of a tabletop with a few items like plates, fruit etc all giving off reflected light. No great range there and it can all be shot with a single exposure. I dont call that an HDR image. Now throw in an open window to the scene and there is now more than a single shot necessary to get it all exposed properly. And for a scene to only need 2 shots means, to me, that its pretty flat lighting.

Also as I understand it its not possible to actually see an HDR image without tone mapping it. Tone mapping allows the image to be seen by present day devices.

 

[spacefuzz]

slick mentioned using GNDs to create HDR. It sure would be nice if they were considered HDR by the general community (since they technically are). I think that would create wider acceptance of the term.

 

[480sparky]

GNDs only work for highly limited type of shots (usually landscapes). Even then they have their limitations.

 

[cgipson1]

slick mentioned using GNDs to create HDR. It sure would be nice if they were considered HDR by the general community (since they technically are). I think that would create wider acceptance of the term.

GND's don't really increase the dynamic range... they just reduce the highlights (sky) to allow better exposure of the foreground without blowing out the highlights... more of a compression of range than an HDR. And like Sparky said, limited application.

 

[Bynx]

Seems to be a complete misunderstanding what HDR is, how its achieved, or what its supposed to do. Wow after all this time. GND filter????

 

[cgipson1]

Seems to be a complete misunderstanding what HDR is, how its achieved, or what its supposed to do. Wow after all this time. GND filter????

<grin>!

 

[spacefuzz]

Seems to be a complete misunderstanding what HDR is, how its achieved, or what its supposed to do. Wow after all this time. GND filter????

Hmm I dont think its a mis understanding of HDR at all. What is HDR? High Dynamic Range. What does that mean? Your range (luminence) is broad, usually broader than what your camera sensor can capture (NOT to be confused with tone mapping). What do you do with an HDR scene? You compress the dynamic range for display somewhere (digital or print).

Then does it matter how you compress your dynamic range to end up with a viewable result? Nope.

Would a GND work for this? Yup. A GND reduces your exposure on part of the scene so you can properly expose everything in a single shot. It is the same thing as stopping down to limit light into your camera and take a bracketed exposure.

Do they only work in certain circumstances? Yup, but so what. why would that make them non hdr?