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Thread: Maintain 16-bit throughout the HDR process

  1. #1
    neverhood311's Avatar
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    May 2010
    I'm from Seattle and I go to school in Utah
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    Maintain 16-bit throughout the HDR process

    I've been doing some HDR stuff lately and I've been plagued by image noise. I've read that HDR photos using only 3 exposures are prone to noise, especially in darker areas of the image, and my Rebel XTi only does 3-exposure bracketing (and I don't feel like venturing into trying to do more by hand).

    Anyways, this is my workflow:
    • I take 3 images in RAW, 2 stops apart.
    • I bring them into Adobe Photoshop CS2 and do Automate>Merge to HDR.
    • I save it in the OpenEXR format. This reduces the file size to around 28 megabytes.
    • I open the .exr file in Qtpfsgui, tonemap it using the default settings for the Manituk algorithm (sometimes boosting the saturation).
    • Then I save that as a .bmp and bring it back into Photoshop and convert it to 16-bit.
    • I'll usually take the middle exposure, overlay it over the tonemapped .bmp, and play with the opacity until it looks good (and then I'll usually do a few other things to the contrast and saturation).

    So the problem, I think, is when I save it and take it to Qtpfsgui. The output from Photoshop's 'Merge to HDR' tool is a 32-bit photo, but when I save it as OpenEXR, 28MB for a 10 megapixel photo doesn't sound like it'll be 32 bits. More like 8. Then when I save the tone-mapped one, it's saved as a .bmp which is also about 28MB. That sounds like another 8-bit photo.

    Does anyone use Photoshop and Qtpfsgui for HDR photos? Can Qtpfsgui import any 32-bit image formats that Photoshop CS2 exports? I know that Qtpfsgui also merges photos to HDR but I like the results from Photoshop alot better. I don't want to go 32-bit -> 8-bit -> 8-bit -> 16-bit -> 8-bit. I'd rather go 32-bit-> 16-bit -> 8-bit.

  2. #2

    Join Date
    Dec 2008
    New Zealand
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    Have a guess :)

    Re: Maintain 16-bit throughout the HDR process

    Quote Originally Posted by neverhood311 View Post
    I've read that HDR photos using only 3 exposures are prone to noise
    It really depends on the dynamic range of the original scene compared to the dynamic range of what you've captured. So it's not a "fixed length" kinda thing.

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