# HDR images



## photo28 (Aug 30, 2008)

Can you make them with Adobe photoshop 7.0.1? I know you have to take three different images in three different settings, but can you explain a little more on how to do that, and a little more specifically.
thanks!


----------



## Garbz (Aug 30, 2008)

No Photoshop CS2 CS3 or use a dedicated HDR tool like Photomatix.

Mind you you could just take two differently exposed images, layer them in photoshop 7 and then apply a gradient mask to the layer. It probably would look better than 99.99% of HDR images anyway.


----------



## Bifurcator (Aug 30, 2008)

You mean "No, _you need_ Photoshop CS2 CS3 or use a dedicated HDR tool like Photomatix."? 


Again though you guys are talking about "tone mapping" and *NOT* HDR. Hehehe, just because 80% of photographers are confused by the two doesn't make them right. An HDR image is 96 bits at least and when displayed on a normal monitor looks no different than a normal 24 bit color exposure.

Also .JPG files cannot be HDR.


----------



## Garbz (Aug 31, 2008)

:er: yes and you need Photoshop CS2 or CS3 to do a HDR merge, which comes out as a 3x32bpp image and can't be saved as a JPEG...

Neither of us were talking about tonemapping.


----------



## Moglex (Aug 31, 2008)

Bifurcator said:


> Again though you guys are talking about "tone mapping" and *NOT* HDR.



No they weren't (although tone mapping is inherently involved at some point in HDR as output).



> Hehehe, just because 80% of photographers are confused by the two doesn't make them right.



Well, *you* certainly seem to be confused!



> An HDR image is 96 bits at least and when displayed on a normal monitor looks no different than a normal 24 bit color exposure.



This is complete and utter nonsense.

It's so far from the truth that I'm not even going to try and explain.

I'd invite anyone who believes what Bifurcator says to google for a source they find authorative and get the true gen.



> Also .JPG files cannot be HDR.



Again, complete and utter nonsense in the generally accepted sense of HDR.

The confusion seems to be caused by some people equating HDR to the tonal resolution and the majority equating it to the compressed tonal range.


----------



## Dao (Aug 31, 2008)

Quoted from Wikipedia

"One problem with HDR has always been in viewing the images. Typical computer monitors (CRTs, LCDs), prints, and other methods of displaying images only have a limited dynamic range. Thus various methods of converting HDR images into a viewable format have been developed, generally called "tone mapping"."

In that case, does that mean HDR image can only be display as LDR image when it is shown in a regular monitor since the limitation of the monitor?






"The rendering software produces a high dynamic range image. When making the JPEG images, one selects a part of that range for display. This is similar to how a conventional camera captures only a portion of the dynamic range of a real physical scene."


hum ..  so I believe JPEG is only a LDR since it only have part of the range of a HDR, so it should not be a HDR.


----------



## Moglex (Aug 31, 2008)

Dao said:


> Quoted from Wikipedia
> 
> "One problem with HDR has always been in viewing the images. Typical computer monitors (CRTs, LCDs), prints, and other methods of displaying images only have a limited dynamic range. Thus various methods of converting HDR images into a viewable format have been developed, generally called "tone mapping"."
> 
> ...



No.

I actually think Wikipedia is rather confusing because it is talking about some abstract concepts that do not really relate to HDR as it applies to photographers in the real world as no output device in common use can  render actual HDR. (It is possible to imagine a scanning laser device that could).

What we are actually doing when we create an HDR image is compressing individual ranges of brightness and mapping them in a non linear manner to the output space. This resultant mapping can be perfectly well handled with a JPG, otherwise you would never be able to see an HDR image on a web page!

To create an HDR image as a photographer uses the term, the software involved creates an image with a greater bit depth than any output device can handle and then maps that into a space that it can. That result can be compressed in any way you like just as can any 'normal' photograph.


----------



## Bifurcator (Aug 31, 2008)

Garbz said:


> :er: yes and you need Photoshop CS2 or CS3 to do a HDR merge, which comes out as a 3x32bpp image and can't be saved as a JPEG...
> 
> Neither of us were talking about tonemapping.



Sure you were, you just didn't know it. 

CS3 handles HDRIs and loads and saves them as radiance (.hdr), OpenEXR (.exr), or Photoshop (.psd) files. It knows tho that there's no way (actual impossibility) to save an HDRI as a JPEG file so the option isn't offered.  Photomatrix Pro won't either. Photomatrix Pro offers .hdr, .exr, and floating point tiff (.tif) for HDRI output. That's all you get.

Now, AFTER you tone-map it and click process then and only then will Photomatrix allow you to save it as a JPEG (or tif 8bit, tif 16bit). The reason for this is that it's no longer an HDRI. 

Trust me. This is my forte'.  This is the kind of stuff I made my bread and butter (CG artist, educator, etc.) on from about 1985 until late 2007.


----------



## Bifurcator (Aug 31, 2008)

Dao said:


> Quoted from Wikipedia
> 
> "One problem with HDR has always been in viewing the images. Typical computer monitors (CRTs, LCDs), prints, and other methods of displaying images only have a limited dynamic range. Thus various methods of converting HDR images into a viewable format have been developed, generally called "tone mapping"."
> 
> ...





An HDRI when displayed on a regular monitor looks just like any normal exposure.  The difference is that the exposure "*R*ange" is very large (or "*H*igh") and thus selecting an exposure to display can be quite "*D*ynamic". 

Imagine loading a 6-bit image and trying to use the exposure tool. There's little or no width or "*R*ange" at all and soon we're clipping the hi or low values. There's more in an 8-bit image but it's still not very dynamic. There is however, more than most photographers think there is - as I often observe in discussions here anyway. In camera created RAW 12 or 14-bit images there is quite allot. We might even say they have a truly *d*ynamic *r*ange. But looking at the 6-bit, the 8-bit, and the 14-bit files (if all were properly exposed) side by side reveals little or no differences. The difference is that when we move the exposure slider we'll have some room (*r*ange) to work with. If we loaded a 14-bit RAW file and saved it as a JPEG it is no longer 14 bits and no longer a RAW file. 

An HRDI is just like that but the range is even greater. There are special 16-bit "Half" HDRIs but mostly only used internally by some video cards - namely Nvidia's "FX" series. So "true" HDRIs are 32-bit (integer or floating types are available) files. If it's not 32-bit, it's not an HDRI. (there are also deeper files but for this discussion let's keep it at 32.  )

An HDRI looks identical to an 8-bit jpeg or a 14-bit RAW files when displayed on a normal monitor if they were all exposed properly. The difference is that the HDR *I*mage has a much *h*igher exposure *r*ange. This means that we can move the exposure slider much farther before we start to see clipping in any of the 3 channels. I does *NOT* mean that it combines, mixes, compresses, or "maps" these various exposure levels into a single displayable range.  That is called "tone mapping".

If we load an HDR *I*mage into any application and do something that allows us to save it as a JPEG then it is no longer an HDRI - just as the RAW seised to be a RAW when it was saved as a JPEG file. JPEGS are limited to 8-bits unless we're talking about JPEG-2000 which is actually a different animal. So you are correct in your assertion that JPEGs are only an LDR format.

The Wiki quotes you pasted are straight forward and correct. In the computer graphics industry it is only photographers where I have seen confusion. For some reason they are under the impression that if several exposure levels are mixed or "tone-mapped" into a single displayable range then that result is somehow an HDR. Nothing could be further from the truth and you nailed it when you asked: "_In that case, does that mean HDR image can only be display as LDR image when it is shown in a regular monitor since the limitation of the monitor?_" - the answer to which is of course, yes. 

When photographers say "it looks like an HDR" what they're really saying whether they know it or not is "It looks tone-mapped." for an HDR file looks no different than an 8-bit jpeg, png, tiff, or etc.


----------



## Garbz (Aug 31, 2008)

If you want to split hairs then we were talking about HDR AND Tonemapping


----------



## Arch (Aug 31, 2008)

Bifurcator, i feel you are over complicating the term 'HDR' which to a newbie, would just simply confuse the subject.

Yes, you are right a HDRI cannot be displayed as a true HDRI if it is an 8bit jpeg file... BUT a true HDRI should also be viewed on a monitor that can display a 32bit file... which just isn't going to happen (certainly not on most peoples home computers to date).

Therefore, the compressed 8bit version of the tonemapped HDR file can and *is* still named a HDRI. 

You can argue the semanitcs, but it still stands that an image made from multiple exposures using the PS 'merge to HDR' command, Photomatix or others and displayed over the internet can still be called a HDR.... if not, you have alot of work to do if you want to go around correcting everyone!


----------



## Bifurcator (Aug 31, 2008)

Garbz said:


> If you want to split hairs then we were talking about HDR AND Tonemapping



OK, hehhe you got me! :thumbup:




Arch said:


> Therefore, the compressed 8bit version of the tonemapped HDR file can and *is* still named a HDRI.
> 
> You can argue the semanitcs,



No, no this is very very far from semantics. Photographers just have it so messed up it's crazy is all. HDR is a file format. Tone-mapping is a process.  What you're saying actually makes no sense. It would be like saying:

Therefore, the compressed 8bit version of the sharpened TIFF file [when saved as a JPEG] can and *is* still named a TIFF. 

Right? Does that make any sense? No, right.  It's a sharpened JPEG. Just like it's a tone-mapped jpeg. It ceased to have anything to do with HDR when it processed and saved as a different file format.


And it's certainly not like I'm posting in every thread where photographers are misusing the term - it's only in threads where people are asking about HDR and tone-mapping. So... they asked.


----------



## Arch (Aug 31, 2008)

Bifurcator said:


> What you're saying actually makes no sense.



What i said makes perfect sense becuase that is what happens!

I said: 'Therefore, the compressed 8bit version of the tonemapped HDR file can and is still named a HDRI.'

I said it is still *named* a HDRI.

This is what im trying to say to you... from a technical viewpoint the said file is NOT a HDRI (nor can you view a real one without a device to view it) BUT... go look around the internet... HDR software sites... pro's porfolios... it can, and is, named a HDR image because it is a representaion of the finished HDR file. 

These images are still refered to as HDRI's even if they technically aren't. Such is our common language... i'v said this for while now, but i think it will only be a matter of time before peoples idea of a 1 RAW tone mapped image IS just refered to as HDR also... even tho me and many others (including yourself) try to tell people otherwise. 

All i was saying is that stating that a Jpeg cannot be HDR is confusing...  yes a jpeg cannot be a finished HDR *file* (or format) but it can be called a HDR if it is a representaion of the true HDRI.


----------



## Moglex (Sep 1, 2008)

Bifurcator said:


> No, no this is very very far from semantics. Photographers just have it so messed up it's crazy is all. HDR is a file format. Tone-mapping is a process.  What you're saying actually makes no sense. It would be like saying:
> 
> Therefore, the compressed 8bit version of the sharpened TIFF file [when saved as a JPEG] can and *is* still named a TIFF.
> 
> ...



I'll say to you exactly what I said to Helen B who has suddenly popped up again, singing from the same hymn sheet as you:

If you want to continue to use HDR in a way that is at odds with the way it is generally used photographically, go ahead. No one can stop you.

Do not, however, expect the rest of the photgraphic world to go along with you. That isn't going to happen. At best you will be considered a tiresome pedant and at worst simply wrong.


The way photographers use HDR is perfectly sensible and consistent with the meaning of the words involved the the TLA.


----------



## Bifurcator (Sep 1, 2008)

Arch said:


> All i was saying is that stating that a Jpeg cannot be HDR is confusing...  yes a jpeg cannot be a finished HDR *file* (or format) but* it can be called a HDR...*



Yeah, I know the issue and you're of course correct that many people (usually only photographers) call it an HDR so they *can* and do. 



> if it is a representaion of the true HDRI.



Now see, this is where I start scratching my head. It never ever can be - ever. Unless it's not tone-mapped at all.  Here's a grab from the other thread.

The first one is tone-mapped (a little extreme but not too different from what many people do.).

The second one is a camera JPG.

The third one is a true HDRI.





See what I'm saying? How is the tone mapped JPEG any kind of representation of the HDRI.  The non-tone-mapped jpeg looks more like the HDRI. HDR files just give you lots more exposure latitude - it's nothing to do with squashing multiple exposure levels into a single display gamut. 

Anyway I should probably clarify that I think this whole issue isn't all that important. It's kinda fun to hash out tho.  It gives us something (I think is) interesting to talk about. :thumbup:


----------



## Moglex (Sep 1, 2008)

Bifurcator said:


> See what I'm saying? How is the tone mapped JPEG any kind of representation of the HDRI.  The non-tone-mapped jpeg looks more like the HDRI. HDR files just give you lots more exposure latitude - it's nothing to do with squashing multiple exposure levels into a single display gamut.



The problem with what you are saying is this:

There are now two completely different meanings to HDR.

They share part of the processing but the photographic HDR does more.

Unless people such as yourself and Helen B start creating a problem where none exists there is no confusion between the two.

The HDR that you are talking about (let's call it 'scientific HDR) is completely useless to photographers as your far right shot above demonstrates.

The term that photgraphers (and the makers of HDR software) refer to applies to a necessarily more complex process that enables the display of an image with a greater range of luminosity than the output device can handle by effectively 'cheating'. That is to say that what you see is not an accurate rendition of the scene as it was lit. But that's hardly anything new for photography, is it?

My piece about HDR from a photographer's perspective explains what is happening by using a scaled up manual example.


----------



## photo28 (Sep 1, 2008)

Bifurcator said:


> Arch said:
> 
> 
> > All i was saying is that stating that a Jpeg cannot be HDR is confusing... yes a jpeg cannot be a finished HDR *file* (or format) but* it can be called a HDR...*
> ...


----------



## Bifurcator (Sep 1, 2008)

Yeah, the 2nd one was sharpened in-camera. I should have turned that off for a comparison like this but I was too lazy.


----------



## dklod (Sep 2, 2008)

Ok, so I have a question in regards to bracketing for this purpose. When I set my camera to +1/-1 for bracketing, what in effect is actually happening to those images?? What settings (if any) are actually being applied inside my camera to change the exposure of those 2 images??


----------



## Moglex (Sep 2, 2008)

dklod said:


> Ok, so I have a question in regards to bracketing for this purpose. When I set my camera to +1/-1 for bracketing, what in effect is actually happening to those images?? What settings (if any) are actually being applied inside my camera to change the exposure of those 2 images??



The camera will actually change the exposure.

It isn't something done in post capture processing.

This is why people say that making an HDR image from one shot 'developed' differently is not HDR. (I don't necessarily agree with them - it's a bit more complicated than that).

So if you have your camera set on AP (say, f11) and it deems the correct exposure is 1/250,when you take the series of shots you'll end up with three shots: (1/125 f11, 1/25 f11, 1/500 f11).


----------



## Bifurcator (Sep 2, 2008)

dklod said:


> Ok, so I have a question in regards to bracketing for this purpose. When I set my camera to +1/-1 for bracketing, what in effect is actually happening to those images??



Well unlike 12-bit and 14-bit camera files or even 16-bit working files, the 32-bit HDR format actually increases the min./max. range values. So you can maybe imagine placing 4 standard histograms end to end for one long (32-bit) one.  When you assemble an HDR from multiple exposures it shifts the values of each frame per-pixel based on it's brightness value plus the exposure bracket value and distributes it into is new place on the expanded HDR histogram.





HDR Histogram​
There's actually more to it than that and I'm paraphrasing for simplicity but that should give you the gist of it. If you're having trouble visualizing it in relation to 8, 12, 14, and 16 bit files thinking of digital sound files may help. Most of us know what sound waves look like in an editor. 8, 12, 14, 16, 24 bit sounds are just chopped up (digitized) into finer slices but the min./max dynamic range (volume) remains the same (0~255) across all formats. Imagine if there was an HDR format for sound (and there actually is btw but...) that the actual dynamic range would increase in such a way where very loud pops or normally over-modulated sounds would not clip off at the top and bottom but would have many times the vertical range. Such it is with image files. Dynamic Range is a different beast than bit depth (per pixel color). Bit depth is the number of steps. Dynamic range is the height of the star case. 




> What settings (if any) are actually being applied inside my camera to change the exposure of those 2 images??



What settings change inside your camera depend on what mode your camera is in for bracketing. Basically it's just increasing or decreasing any of: ISO, Shutter, and/or Aperture depending - I think. Others will know more about this for your specific model and bracketing type.


----------



## Moglex (Sep 2, 2008)

Bifurcator said:


> Well unlike 12-bit and 14-bit camera files or even 16-bit working files, the 32-bit HDR format actually increases the min./max. range values.



No.

True, a 32 bit HDR format will increase the range but that is just like moving from a 12 bit to a 14 bit sensor.

The 12 bit sensor will allow a maximum value of 4,096 and a 14 bit one will allow a maximum value of 16,384.

This compares with a maximum of 256 displayable values for a monitor, somewhat less for an inkjet printer.



> Imagine that is there was an HDR for sound (and there actually is btw but...) that the actual dynamic range would increase in such a way where very loud pops or normally over-modulated sounds would not clip off at the top and bottom but would have many times the vertical range. Such it is with image files. Dynamic Range is a different beast than bit depth (per pixel color). Bit depth is the number of steps. Dynamic range is the height of the star case.



Bizzarely you seem to be making *exactly* the same mistake os Helen B when you say range is seperate thing to bit depth.

It may actually be easier to stick with the sound example to demonstrate why what you say above is incorrect.

For simplicities sake, let's assume the electronic make no noise themselves - this is never the case but it simplifies the explanation.

The actual range of sound loudness actually depends on how powerful your system is and how loud you've got the volume control. Obviously this is no help in defining dynamic range so what we use is the difference in sound level between the quietest sound that can be reproduced and the loudest. 

So if you have an 8 bit system (which sounds pretty abysmal) the loudest sound is 256 times louder than the quietest sound.

If you have a CD system - which is 16 bits - the loudest sound is 16,384 times louder than the quietest sound.

If you have 24 bit audio the the loudest sound is 16,777,216 times louder than the quietest sound

But none of this has any actual bearing on the sound level at which you listen to the audio (although you wouldn't want to listen to 8 bit at very high volume :mrgreen. It is nontheless what determines the dynamic range - see Here under examples of usage, Audio.

For dynamic range, the exact same logic applies to light as does to sound.


----------



## Bifurcator (Sep 2, 2008)

I'm so glad I can't read the above message. The ignore list is a wonderful invention. I'm told however that it's full of accusations, inaccuracies, and false information - so let the reader beware.


----------



## Moglex (Sep 2, 2008)

Bifurcator said:


> I'm so glad I can't read the above message. The ignore list is a wonderful invention. I'm told however that it's full of accusations, inaccuracies, and false information - so let the reader beware.


If there are any inaccuracies or false information I'm sure they will be pointed out in due course.

As things stand you have made certain statements of fact and logic with which I disagree.

I have given detailed reasons why I disagree with those statements (including a citation that directly contradicts one of your assertions).

This moves the debate forward.

Your rather puerile head in the sand approach does not.


----------



## Steph (Sep 2, 2008)

Yet another HDR thread going slowly down the drain...


----------



## Battou (Sep 2, 2008)

Steph said:


> Yet another HDR thread going slowly down the drain...




yup...


----------



## Moglex (Sep 2, 2008)

Steph said:


> Yet another HDR thread going slowly down the drain...



I apologise for that but there is little I can do about it.

At first glance you may take the view that it is just pointless squabbling.

However, my contribution in post 22 was a genuine attempt at debating, addressing points that I genuinely believe that Bifurcator has got wrong.

His response (to which I have alerted the moderators) could most charitably be described as heckling.

You my wish to ask yourself why, if someone has discovered that my post was full of 'inaccuracies, and false information', they did not post pointing them out, rather than allegedly PMing Bifurcator.


----------



## dklod (Sep 2, 2008)

You are both obviously very informed on this subject, regardless of one thoughts about the other. Unfortunately, Im still very green in this area, but copious amounts of reading I do every day on the subject is helping me to try and understand what it is you are explaining to me, to us beginners. 

I no longer use the bracketing, instead i shoot 3 or 4 images and change the shutter purely because I could not see how changing something in photoshop would be any different to exposure compensation in the camera. Why you would have it change the aperture or ISO, I dont know. Having images with different DOF and possible noise makes no sense to me if you are going to layer them over each other. 

Above, Moglex mentions some values. Its the first time Ive seen someone mention it. Im only bringing it up because earlier today I did some research into RAW format. Why?? Because people said it was lossless but failed to mention what it was exactly that is kicked to the curb during processing in your camera. When I saw those figures, I knew I had seen them mentioned in the article I read. It helped me understand and I hope it helps others. So to avoid a public flogging for raising an old debate, I'll just post the link and be on my way.  

http://www.luminous-landscape.com/tutorials/understanding-series/u-raw-files.shtml

Thank you both for addressing my questions.


----------



## tirediron (Sep 2, 2008)

Moglex said:


> His response (to which I have alerted the moderators) could most charitably be described as heckling.


 
Seems rather a statement of fact to me, however this statement, "_Your rather puerile head in the sand approach does not..._ " is downright insulting and something for which an apology should be offered.


----------



## pm63 (Sep 2, 2008)

See what a load of nonsense all this HDR stuff brings?

Single exposures are the way to go.


----------



## Jim Benton (Sep 2, 2008)

tirediron said:


> Seems rather a statement of fact to me,



If you think the statement that his article was full of  inaccuracies, and false information was a fact, please tell us all what these are as I can't see anything wrong and I don't want to go away with the wrong information.



> however this statement, "_Your rather puerile head in the sand approach does not..._ "


Oh, come on!

Putting someone in your kill file is certainly a 'head in the sand' approach. Maybe a sensible thing to do in some cases but then taking pot-shots at the person you've kill filed is childish in the extreme.

If someone has told Bifurcator about various errors, why did neither the informant or bifucator expose them rather than just making vague, unsupported accusations?


----------



## Dao (Sep 2, 2008)

Got this information from HdrSoft, the maker of Photomatirx.

----------------------------------------------------------------------------
Direct Quote:

What is an HDR image?


      The Dynamic Range of real-world scenes can be quite high -- ratios of 100,000:1 are common in the natural world. An HDR (High Dynamic Range) image stores pixel values that span the whole tonal range of real-world scenes. Therefore, an HDR image is encoded in a format that allows the largest range of values, e.g. floating-point values stored with 32 bits per color channel.


      Another characteristics of an HDR image is that it stores linear values. This means that the value of a pixel from an HDR image is proportional to the amount of light measured by the camera. In this sense, HDR images are scene-referred, representing the original light values captured for the scene.


      Whether an image may be considered High or Low Dynamic Range depends on several factors. Most often, the distinction is made depending on the number of bits per color channel that the digitized image can hold. However, the number of bits itself may be a misleading indication of the real dynamic range that the image reproduces -- converting a Low Dynamic Range image to a higher bit depth does not change its dynamic range, of course.

·     8-bit images (i.e. 24 bits per pixel for a color image) are considered Low Dynamic Range.

·     16-bit images (i.e. 48 bits per pixel for a color image) resulting from RAW conversion are still considered Low Dynamic Range, even though the range of values they can encode is much higher than for 8-bit images (65536 versus 256). Converting a RAW file involves applying a tonal curve that compresses the dynamic range of the RAW data so that the converted image shows correctly on low dynamic range monitors. The need to adapt the output image file to the dynamic range of the display is the factor that dictates how much the dynamic range is compressed, not the output bit-depth. By using 16 instead of 8 bits, you will gain precision but you will not gain dynamic range.

·     32-bit images (i.e. 96 bits per pixel for a color image) are considered High Dynamic Range. Unlike 8- and 16-bit images which can take a finite number of values, 32-bit images are coded using floating point numbers, which means the values they can take is unlimited. It is important to note, though, that storing an image in a 32-bit HDR format is a necessary condition for an HDR image but not a sufficient one. When an image comes from a single capture with a standard camera, it will remain a Low Dynamic Range image, regardless of the format used to store it.



      There are various formats available to store HDR images, such as Radiance RGBE (.hdr) and OpenEXR (.exr) among the most commonly used. See Greg Ward's HDR Image Encodings page for an excellent overview of HDR formats. 
----------------------------------------------------------------------------


Being a beginner, and after I read the information I got from Wikipedia and HdrSoft, I tend to lean more on Helen and Bifurcator side.   Moglex, don't get me wrong, I do not mean you are wrong, and I DO really appericate you bring this subject up so that I can do more reading.  It's just that the information I read match better with what Bifurcator said.  Maybe I just dumb and not quite get some of the information you provide.


----------



## Dao (Sep 2, 2008)

BTW, the FAQ from HDRSoft has some good info on HDR images for Photography.

http://www.hdrsoft.com/resources/dri.html


----------



## Moglex (Sep 2, 2008)

Dao said:


> Being a beginner, and after I read the information I got from Wikipedia and HdrSoft, I tend to lean more on Helen and Bifurcator side.   Moglex, don't get me wrong, I do not mean you are wrong, and I DO really appericate you bring this subject up so that I can do more reading.  It's just that the information I read match better with what Bifurcator said.  Maybe I just dumb and not quite get some of the information you provide.



Don't worry, you're not dumb! This is really pretty complicated stuff. I'm always prepared to admit that it might be me that has it wrong - all I ask is that people point out particular errors of fact or logic rather than just saying "I'm right and you're wrong" or putting up a smokescreen by concentrating on off topic factors.

Firstly I'd like to address a factual error in what you've quoted. When they say: "32-bit images are coded using floating point numbers, which means the values they can take is unlimited.", this is quite simply completely incorrect. A 32 bit number can store approximately 4.3 billion values. It can, however, store values (much) bigger than 4.3 billion but it is still limited to ~4.3 billion values.

I think the confusion (yours, mine, Helen's, Bifurcators?) stems from this (or something like it): "However, the number of bits itself may be a misleading indication of the real dynamic range that the image reproduces -- converting a Low Dynamic Range image to a higher bit depth does not change its dynamic range, of course."

This is perfectly correct, but you have to be careful to note that it only works one way:

The number of bits is not necessarily an indication of the dynamic range - true.

A higher dynamic range does not necessarily require a greater minimum number of bits than a low dynamic range - false.

In the earlier post I tried to very carefully explain why it is the number of bits (or, to be more accurate, the number of *significant* bits) that determine the dynamic range of a system (and even provided a link to a source that stated exactly that). This is somthing that Helen B specifically denied.

It would be very helpful if you could explain exactly why you tend to lean towards her version of DR rather than mine (and the source I quoted). It will either help me understand where I'm wrong or help me explain why I'm not.


----------



## tirediron (Sep 2, 2008)

bifurcator said:
			
		

> I'm so glad I can't read the above message. The ignore list is a wonderful invention. I'm told however that it's full of accusations, inaccuracies, and false information - so let the reader beware.


Hmmm, "I'm glad", "I'm told"; it seems reasonable to assume that those are statements of fact with respect to Bifurcator's feelings. Whether you, I, or anyone agrees or disagrees with them is irrelevant. There is no attack made on anyone; perhaps a subtle insinuation at most. Entirely different however, than telling someone they are acting childishly. You can hardly disagree Moglex's comment is aimed directly at someone. Again, concurrence or not with the statement has no bearing on the situation. 

I'm not denying Moglex seems to have a great deal of knowledge on the matter, however other people whom I know to be very knowledgable disagree with him. One side is right, one side is wrong. I see no reason why Moglex needs to resort to insulting remarks.


----------



## Jim Benton (Sep 2, 2008)

LOL.

So if Moglex had said that he'd been told that Bifurcator was being childish that would have been a statement of fact and OK?

I don't see why Bifurcator's being rude about Moglex's post is acceptable just because he mentions a third party.

The real problem, though is that Birfurcator, Moglex and Dao have all made posts about the subject in hand whereas all you're doing is talking about posts, a job I would have though would be much better left to the moderators who could have a quiet word with Bifurcator and/or Moglex if they think they've overstepped the bounds.

It seems as if I'm now also guilty of posting about posts rather than the subject but I really want to know if anyone has concrete facts or arguments to counter those of Moglex as it's a very interesting subject and I'd like to go away with the correct information and I don't want to see this thread stopped in its tracks like yesterdays.


----------



## Bifurcator (Sep 2, 2008)

Dao said:


> Got this information from HdrSoft, the maker of Photomatirx.
> 
> ----------------------------------------------------------------------------
> Direct Quote:
> ...



Range values here are the number of steps - not the height of the staircase. 65534 steps (and the two floors )  

As should be made obvious from the *blue* sentence below quoted  from the same document.



> Converting a RAW file involves applying a tonal curve that compresses the dynamic range of the RAW data so that the converted image shows correctly on low dynamic range monitors. The need to adapt the output image file to the dynamic range of the display is the factor that dictates how much the dynamic range is compressed, not the output bit-depth. *By using 16 instead of 8 bits, you will gain precision but you will not gain dynamic range.*
> 
> ·     32-bit images (i.e. 96 bits per pixel for a color image) are considered High Dynamic Range. Unlike 8- and 16-bit images which can take a finite number of values, *32-bit images are coded using floating point numbers, which means the values they can take is unlimited*. It is important to note, though, that storing an image in a 32-bit HDR format is a necessary condition for an HDR image but not a sufficient one. When an image comes from a single capture with a standard camera, it will remain a Low Dynamic Range image, regardless of the format used to store it.



As you can see number of steps and staircase height are two different things - as obviously the 32bit HDR staircase isn't infinitely high. 



> There are various formats available to store HDR images, such as Radiance RGBE (.hdr) and OpenEXR (.exr) among the most commonly used. See Greg Ward's HDR Image Encodings page for an excellent overview of HDR formats.
> ----------------------------------------------------------------------------
> 
> 
> Being a beginner, and after I read the information I got from Wikipedia and HdrSoft, I tend to lean more on Helen and Bifurcator side.   Moglex, don't get me wrong, I do not mean you are wrong, and I DO really appericate you bring this subject up so that I can do more reading.  It's just that the information I read match better with *what Bifurcator said*.  Maybe I just dumb and not quite get some of the information you provide.





But the way some documents are worded does indeed make it hard to understand and the number of different formats (HDR-Half, HDR, LDR in all the various bit depths) doesn't help. Like the document dklod quoted from luminous landscape used confusing terminology and could be construed to mean either higher stairs or more steps depending what assumptions you brought to it.  The above document is much more clear and states precisely "_By using 16 instead of 8 bits, you will gain precision but you will not gain dynamic range._" meaning more steps, same stair height. HDR is higher stairs and infinite steps.


----------



## Moglex (Sep 2, 2008)

Bifurcator said:


> Range values here are the number of steps - not the height of the staircase. 65534 steps (and the two floors )



Actually, 65,535 steps. Neither floor raises the value and the number of 'steps from 0 tp 2^n is always 2^n - 1.




> As should be made obvious from the *blue* sentence below quoted  from the same document.
> 
> {quoted: *32-bit images are coded using floating point numbers, which means the values they can take is unlimited*}.



Amazingly, Bifurcator has picked the one part of the quoted documant that is absolutely and unequivocaly incorrect.

As anyone who has done computer science at even the most basic level should be able to assure you: No number represented by a finite number of bits can possibly take an unlimited number of values.

That is so fundamental it beggars belief that someone who claims to have a computer science degree, as Bifurcator has, could possibly make such a mistake.



> As you can see number of steps and staircase height are two different things


Blindingly obvious which is why you cannot actually see that in the quoted text. 

What they've actually said is that *becase the imaging device cannot handle more that 8 bits per channel* even if you use 16 bits it will be converted with a dynamic range suitable for the output.



> as obviously the 32bit HDR staircase isn't infinitely high.



And neither does it have an infinite number of steps!



> The above document is much more clear and states precisely "_By using 16 instead of 8 bits, you will gain precision but you will not gain dynamic range._" meaning more steps, same stair height.



The document also says: "*The need to adapt the output image file to the dynamic range of the display is the factor that dictates how much the dynamic range is compressed*". This is vital. As someone quoted in a document earlier, more bits does not necessarily mean greater dynamic range. In the case of a conversion from raw to an output intended for a display device it won't because the display device could not handle the range.

That does not mean that you cannot get higher dynamic range by creating a 16 bits/channel image.



> HDR is higher stairs and infinite steps.



No it isn't.

Anyone who doesn't believe me just ask any reasonably competant computer science student. No computer has ever been built that is capable of holding a number than can take an infinite range of values (steps).


----------



## LaFoto (Sep 2, 2008)

Oh well, I take it you better like all the HDR-threads to be closed. So be it. Sigh...


----------



## Arch (Sep 2, 2008)

yea guys, rather than see this thread locked, i would appreciate it if you could try and stick to the technical facts (which im sure we can all find intriguing) rather than argue on a personal level... so from now on please stop with the 'MRsmith said this.. which is wrong'... just expalin your side and your findings and if people don't buy it then its thier problem.

You may continue (and please do) if you can abide by this request. Thankyou.


----------



## photographyaddict (Sep 2, 2008)

There are some really great tutorials on YouTube. 

[ame]http://www.youtube.com/watch?v=CVuDbcAfN_I&feature=related[/ame]

(This one involves CS3) 

I think the hardest part is getting the bracketing right with the initial photography. Have to make sure you get the best range of lighting.


----------



## prodigy2k7 (Sep 2, 2008)

I love these HDR debates. You are all wrong, how about that


----------



## Moglex (Sep 3, 2008)

prodigy2k7 said:


> I love these HDR debates. You are all wrong, how about that



That wouldn't surprise me in the least.


----------

