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Author Topic: HDR using one shot  (Read 16244 times)

RFPhotography

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Re: HDR using one shot
« Reply #20 on: August 17, 2011, 07:44:22 am »

Sorry, GL but I don't agree.  One of the technicalities that you're either not considering or purposely leaving out is that HDR images are 32 bit.  A camera that can capture 100 stops of brightness but does so in 12, 14 or 16 bit isn't capturing HDR.  

For methods that don't take the resulting image into a 32 bit space JP Caponigro's term XDR, eXtended Dynamic Range, is more appropriate.  

I'd go further to say that if some form of blending method isn't needed, or if some form of GND filtering isn't needed and the sensor can capture the entire brightness range of the scene being photographed that we're out of the realm of either HDR or XDR and into a 'normal' DR.  If the sensor can capture it then it's the 'normal' DR of the sensor.  Nothing High or eXtended about it.

I'm not going to, and frankly can't, get into a 'numbers' debate.  I'm a photographer not a physicist and while LL is the web home of the measurebators I don't happen to be one of them.  From a purely visual standpoint I don't buy into your supposition but I'm not going to argue with the math because I can't.  But as it is, I don't know where the '20' comes from in your equation nor do I know where the '6 stops' comes from.  I also don't know why the log equation is being raised to the .5 exponent.  

Eric's point about tonemapping is a good one.  And it's one that I've made in the past and has been discussed if not in this thread then in another one on here recently.  Tonemapping is really just a fancy word for editing.
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Guillermo Luijk

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Re: HDR using one shot
« Reply #21 on: August 17, 2011, 11:22:44 am »

Sorry, GL but I don't agree.  One of the technicalities that you're either not considering or purposely leaving out is that HDR images are 32 bit.  A camera that can capture 100 stops of brightness but does so in 12, 14 or 16 bit isn't capturing HDR.

32 bit HDR formats are not needed to do HDR. I think again you are putting a tecnique (multiexposure first, now using floating point formats for tone mapping) as a part of the definition of a concept which is much wider, and cannot be restricted to simplistic rules so as which tools you used. As Eric said: 'HDR is a somewhat arbitrary term to describe the idea of "more DR than usual"'.

Who says you have to multiexpose to achieve that? who says you have to use 32-bit floating point formats to achieve that? why not 64-bit integer?. I have demonstrated that multiexposure is not necessary to capture what is considered a HDR scene (example of the 5D2 and the small format output), and I have demonstrated 32-bit floating point formats are not needed to hold HDR data (just download superhdr.tif, an integer 16-bit TIFF containing a scene with more than 16 stops of DR ready to be tone mapped). I do my HDR's starting from a unique 16-bit TIFF, and tone map them using regular PS tools (basically masked curve layers).



Regarding the equations, they are basic equations but explaining them is out the scope of this thread. You will have to believe them in this case.

Regards
« Last Edit: August 17, 2011, 11:34:50 am by Guillermo Luijk »
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Peter_DL

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Re: HDR using one shot
« Reply #22 on: August 17, 2011, 12:08:29 pm »

I understand it now: it is the lack of information in the original shot that's killing my idea of being able to do HDR with copies of this on shot.

Not necessarily.

To make best use of the given information in one shot, may not always be possible with the on-board tools of a given Raw converter,
and may require HDR-typical tone mapping techniques.

http://imagingpro.wordpress.com/2008/12/03/expanding-the-dynamic-range-of-a-single-raw-file/

Peter

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RFPhotography

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Re: HDR using one shot
« Reply #23 on: August 17, 2011, 12:33:59 pm »

Well, in the end I think we're talking about the same thing GL, just using different terms to do it.  Yes, I'm restricting HDR to those formats that are considered High Dynamic Range and those are 32 bit file types such as .exr, .hdr, 32 bit .tiff and 32 bit .psd.  Anything that doesn't go into 32 bit and using techniques like layers and masking I put into the category of, as I noted earlier, XDR.  HDR isn't an arbitrary term.  It has become so, like Ski-doo or Kleenex or Xerox and like those it's become the manner of describing all extended dynamic range methods but also like those others, it's not technically correct.

As far as whether your equation is 'basic' I guess that depends on the background and point of view.  I can bootstrap a yield curve on the back of a cocktail napkin but I don't think many people would consider that as 'basic' math either.  ;D
« Last Edit: August 17, 2011, 12:36:03 pm by BobFisher »
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PeterAit

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Re: HDR using one shot
« Reply #24 on: August 17, 2011, 03:12:47 pm »

It seems to me that the term HDR has come to mean the melding of 2 or more differently exposed images olf the same scene. An individual image may contain a wide dynamic range, and we can deal with that using curves and other standard techniques. It's when you have 2 or more differently exposed images of the same scene that you need specialized software and techniques to create the final image. This is what we are, or should be, talking about.
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hjulenissen

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Re: HDR using one shot
« Reply #25 on: August 17, 2011, 03:58:34 pm »

This discussion is much like discussing the term "broadband". Does it mean >640kbps? Does it mean fixed pricing? Or does it just mean "whatever speed that 30% of the users cannot afford at any time"? I am sure there are government agencies spending lots of man-hours trying to define the semantics, but in the end, what matters to me is what speed/characteristics I have, not what it is called.

I believe that HDR, in this context, as others have said, only means "more dynamic range than usual". There are/will be camera sensors that claim to do single-shot "HDR" (due to high native DR), no matter if it is saved to 14,16 or 24 bit integers. Exposure stacking is no direct consequence of "HDR" but an indirect one: if you want to capture better DR than usual, you may have to use unusual methods (ie stacking).

In the end, what matters most to me is that the recording device is capable of faithfully recording scenes whose dynamic range cannot directly be appreciated on todays LDR display and paper. This means that the high recorded DR can be used to:
1. Do image processing on a "linear" recording of the scene (even if the final output is clipped to LDR)
2. Postpone choices about exposure to post-processing. The LDR window can be moved up and down according to taste.
3. Fancy tone-mapping algorithms can be used to try to squeeze the impression of HDR into the limited LDR display/paper
4. The scene is captured for posterity (and possible improved display/paper tech)

I believe that fancy tonemapping algos is trickling into regular single-shot raw developers, therefore it may make sense to use the word "tonemapping" for that kind of operations.

-h
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Guillermo Luijk

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Re: HDR using one shot
« Reply #26 on: August 17, 2011, 04:08:14 pm »

I believe that fancy tonemapping algos is trickling into regular single-shot raw developers, therefore it may make sense to use the word "tonemapping" for that kind of operations.

Regarding this, I think the more DR cameras can capture in a single shot, users will be wanting to enjoy it right from their RAW developer because they will now the information is there (I know many users reporting to be happy for doing 99% of their photographic work without leaving LR), and therefore tone mapping capabilities (in the sense you mean) will necessarily improve in RAW converters with more advanced algorithms. My ACR CS2 doesn't have highlight and shadow recovery sliders for instance.

This can lead to RAW converters becoming direct competitors of today's specialized tone mapping software such as Terrormatix.

Regards
« Last Edit: August 17, 2011, 04:10:49 pm by Guillermo Luijk »
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PeterAit

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Re: HDR using one shot
« Reply #27 on: August 17, 2011, 05:27:06 pm »

This discussion is much like discussing the term "broadband". Does it mean >640kbps? Does it mean fixed pricing? Or does it just mean "whatever speed that 30% of the users cannot afford at any time"? I am sure there are government agencies spending lots of man-hours trying to define the semantics, but in the end, what matters to me is what speed/characteristics I have, not what it is called.

I don't think your analogy is a good one. HDR is clearly and appropriately defined as the technique of obtaining a greater DR by combining 2 or more differently exposed images of the same scene. This requires specialized techniques and specialized software, and is usefully distinguished from applying traditional digital manipulation techniques to get the desired DR from a single image.
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hjulenissen

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Re: HDR using one shot
« Reply #28 on: August 17, 2011, 05:29:28 pm »

I don't think your analogy is a good one. HDR is clearly and appropriately defined as the technique of obtaining a greater DR by combining 2 or more differently exposed images of the same scene. This requires specialized techniques and specialized software, and is usefully distinguished from applying traditional digital manipulation techniques to get the desired DR from a single image.
We seem to be disagreeing on semantics, lets put that to rest.

-h
« Last Edit: August 17, 2011, 05:40:58 pm by hjulenissen »
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hjulenissen

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Re: HDR using one shot
« Reply #29 on: August 17, 2011, 05:36:38 pm »

Regarding this, I think the more DR cameras can capture in a single shot, users will be wanting to enjoy it right from their RAW developer because they will now the information is there (I know many users reporting to be happy for doing 99% of their photographic work without leaving LR), and therefore tone mapping capabilities (in the sense you mean) will necessarily improve in RAW converters with more advanced algorithms. My ACR CS2 doesn't have highlight and shadow recovery sliders for instance.

This can lead to RAW converters becoming direct competitors of today's specialized tone mapping software such as Terrormatix.

Regards

I agree. raw files and "HDR" files are both essentially linear representations of a scene with more DR than paper/displays. The difference is only in degree, not in nature. It only makes sense that the art/science of semi-automatically mapping them to LDR is unified.

I too enjoy the luxury of working mostly within LR. My only gripe is locking myself into a proprietary, closed database. I would much prefer that the edits and organization was stored into an open format (Adobe would still be free to implement the gui and signal processing closed).

-h
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torger

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Re: HDR using one shot
« Reply #30 on: August 31, 2011, 07:25:14 am »

Making different exposures of a single RAW file and combine them, that is tone-map the image in a non-linear way, is indeed possible and sometimes quite useful.

I sometimes do it, especially in landscape photography, but the result is more of dodge-and-burn and rarely a cartoon-like HDR look.

Some RAW developer software now has built in functions for dodge and burn and local adjustments so you don't need to combine several "exposures" in external software, but my favourite RAW software (rawtherapee) does not have it so I have to use this technique.

Concerning dynamic range, the RAW file of a modern camera indeed has more than can be represented in a print, so doing some HDR-like tone-mapping may be relevant. If you want t call it HDR or not when using only one shot I don't really care, but most will associate HDR to bracketed shots.
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Fine_Art

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Re: HDR using one shot
« Reply #31 on: September 13, 2011, 07:05:17 pm »

This is a HDR right out of the Sony A55 (downrezed in Paint). The original is quite spectacular for its realism. It does not look like one of those industrial grunge HDRs. I no longer feel I have to try to learn HDR software. If the shot requires HDR, my camera can handle it.
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Jakub

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Re: HDR using one shot
« Reply #32 on: November 05, 2011, 10:16:33 pm »

Check out John Neel @ www.pixiq.com.  John (one of the contributors) to PIXIQ has a 3-part blog post
on SS (single-shot) HDR:   http://www.pixiq.com/article/ss-hdr-my-way-part-1
John is very innovative and is one of the more prolific contributors to the Pixiq site.

cheers!
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Walter
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RFPhotography

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Re: HDR using one shot
« Reply #33 on: November 06, 2011, 07:38:02 am »

He probably could have got it down to a single post if he'd trashed all the talk about how he doesn't follow rules and does his own thing and doesn't do what the software engineers tell him to do and how he doesn't follow rules and that he does his own thing and that rules are made to be broken and well, who needs rules.  ::)
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