HDR images

Discussion in 'Graphics Programs and Photo Gallery' started by photo28, Aug 30, 2008.

  1. photo28
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    photo28 New Member

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    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!
  2. Garbz
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    Garbz New Member

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    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.
  3. Bifurcator
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    Bifurcator New Member

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    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.
  4. Garbz
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    Garbz New Member

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    :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.
    Last edited: Aug 31, 2008
  5. Moglex
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    Moglex New Member

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

    Well, you certainly seem to be confused!

    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.

    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.
    Last edited: Aug 31, 2008
  6. Dao
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    Dao Well-Known Member

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    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.
  7. Moglex
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    Moglex New Member

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    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.
  8. Bifurcator
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    Bifurcator New Member

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

    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. ;)
  9. Bifurcator
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    Bifurcator New Member

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    An HDRI when displayed on a regular monitor looks just like any normal exposure. The difference is that the exposure "Range" is very large (or "High") and thus selecting an exposure to display can be quite "Dynamic".

    Imagine loading a 6-bit image and trying to use the exposure tool. There's little or no width or "Range" 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 dynamic range. 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 (range) 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 Image has a much higher exposure range. 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 Image 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.
    Last edited: Aug 31, 2008
  10. Garbz
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    Garbz New Member

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    If you want to split hairs then we were talking about HDR AND Tonemapping :p
  11. Arch
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    Arch Damn You! Staff Member

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    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! ;)
  12. Bifurcator
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    Bifurcator New Member

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    OK, hehhe you got me! :thumbup:


    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. ;)
    Last edited: Aug 31, 2008
  13. Arch
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    Arch Damn You! Staff Member

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    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.
  14. Moglex
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    Moglex New Member

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    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.
  15. Bifurcator
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    Bifurcator New Member

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    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.

    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.

    [​IMG]

    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:
    Last edited: Sep 1, 2008

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