On Wed, 15 Sep 2004, Gerhard Fuernkranz wrote:
Gerhard Fuernkranz wrote:So I'm also wondering, whether 16-bit precision is sufficient for very dark colors in HDR images, particularly in conjunction with linear luminance color spaces, like e.g. an XYZ PCS?
The answer is it depends on the range of values the 16 bits represent,
I fully agree, it depends on the desired dynamic range. I just don't have a feeling, which dynamic range is "typically" desired for a HDR image (compared to a "normal" image). Do you (or somebody else) know, how many differently exposed shots are usually stitched together to form a HDR image, and what's a typical exposure ratio between the brightes and the darkest of these shots (1:10? 1:100? 1:1000? 1:10000? ...)?
I claim absolutely no expertise in HDR images, but it seems to me that CMS is all about color reproduction on real-world devices. While I understand that CRT-based devices exist which can support a dynamic range of up to 1:20000, most devices do not even come close to that. If a device's colorspace can not support it, then a HDR image will appear no different than any other image.
The primary advantage of HDR image technologies is the ability to store/adjust/manipulate images without fear of saturation or clipping. Images may contain useful content in very dark or very bright regions which otherwise appear black or white. Probably CMS profiles can be developed (or exist) which are optimized for supporting HDR images, but as soon as an image is targeted for a output device, it is limited by the ability of that output device. Part of the task for preparing a HDR image for output on a real-world device is to adjust the image so that the desired characteristics of the image will appear correct on an output device (e.g. by flattening/reducing the dynamic range in regions of the image). This adjustment is best done in the HDR image's native representation.
Bob ====================================== Bob Friesenhahn [EMAIL PROTECTED] http://www.simplesystems.org/users/bfriesen
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