HDR

Discussion in 'Digital Discussion & Q&A' started by Xmetal, Jun 19, 2006.

  1. Xmetal

    Xmetal TPF Noob!

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    I did a search after seeing the Library pictures thread in the general gallery and couldn't find anything on the HDR technique. :???:

    What is HDR?
    What does the letters HDR stand for?
    How does it work?
    Can I do HDR images with my garden-variety EOS 350D? :lol:


    Many thanks in advance for answers/solutions. :)
     
  2. Digital Matt

    Digital Matt alter ego: Analog Matt

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    HDR means "High Dynamic Range". It's the term for taking multiple exposures of a scene and merging them in PS to increase the dynamic range. Anyone can do it with any camera, and any version of photoshop. The term HDR has really become popular because now in Photoshop CS, there is an HDR function in which you can open several bracketed images, and it will automatically merge them for you.
     
  3. Arch

    Arch Damn You! Staff Member Supporting Member

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    Here is a link to one of my HDR threads were i give an explination of it...... its not the best subject matter for HDR..... but gives you a general idea.

    [​IMG]

    But to summerise; HDR means - high dynamic range, and its a technique were you take a series of bracketed exposures of the same scene and combine them to create the 'best of both worlds' in a single image. By merging the bracketed exposures, the final image covers the whole tonal range of the scene..... from shadow detail to highlight detail, without having to make do with the standard tonal range from exposing for one or the other.

    so combined, the final image is a perfectly exposed 'hybrid' of the scene with 32bit of tonal range.

    If you have CS2 its easy to create one using any SLR...... as CS2 has a 'merge to HDR' command. ;)

    edit:..... matt beat me too it..... but its about time we had a proper HDR thread :)
     
  4. Digital Matt

    Digital Matt alter ego: Analog Matt

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  5. Mohain

    Mohain TPF Noob!

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    CS2 will produce an HDR image from bracketted exposures. The exposures will need to be 2 stops apart.

    There is a PS plug-in or stand alone program called Photomatix which will also produce a (very different!) HDR image for you. The pro version will merge differently exposed images processed from the same RAW file.

    Or you can use Luminosity masks (amongst other things) to do it in PS.

    Cheers,

    Mohain
     
  6. Arch

    Arch Damn You! Staff Member Supporting Member

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    Good links!

    Here's one that i find good for HDR technique, and has a full discription to what it does ..... Here

    Xmental..... it should be good for you to try.... although a little time consuming, i'v heard that its a good method for car photog because you can get a nice finish to shiny surfaces.
     
  7. Xmetal

    Xmetal TPF Noob!

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    I really wish people wouldn't call me that. :er:

    So for example (i'm a little vague on exposure bracketing):

    You shoot the same subject 3 times (depending), once to get the fore-ground, the next on the subject and the last to match the background - then it all layers together to create the 'perfect' image. How far off the mark am I? :mrgreen:

    Shutter speeds are dependent on the lighting scenario, i'm guessing?


    Edit: kinda glad I kicked this off now! :D

    Edit...again: I'm using Photochop CS2. :twisted:
     
  8. Arch

    Arch Damn You! Staff Member Supporting Member

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    sorry, xmetal :lol:

    All you do in basic terms is, take your shot with normal exposure..... then take another underexposed by two stops by JUST using shutter speed (so it needs to be firmly fixed on a tripod). Dont use aperture, because you'll alter the dof..... then take it down another two stops...... at this point dont worry about what the images are looking like..... (they will have huge dark areas)..... just keep going..... adobe recomend a minimum of 3 exposures to use with the 'Merge HDR' command to achive decent tonal range..... but 6,7 or 8 shots is even better.

    There are a few ways you can do this.... (this is where experimentation comes in) but the last HDR image i did, i used 7 exposures and the last one was very dark...... but there is still information there for the HDR conversion to use, so dont be shy with it. Another way is to expose normally and then overexpose by two stops..... and then again by another 2 etc....this will ensure you get all the shadow detail...... so it depends what your shooting.

    Once you have your images in your cam...... open them all up..... but DONT adjust any of the exposure/contrast/white bal......etc..... just leave them as the camera captured them..... if you shot RAW, then uncheck all the auto exposure options..... before saving them as tiffs.

    Then if you have cs2 go to 'file'...... 'automate'......'show all menu items'.... 'merge to HDR'...... and open all the source files (your unaltered tiffs).... and the processing will begin. If not then use photomatix or similar like mo suggested. :mrgreen:
     

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