Originally posted by Lowell Goudge HDR is essentually as you discussed, 3 or more shots each exposed correctly for a portion of the scene. and added together using masks for the incorrect exposure areas.
Be careful not to confuse further! (Or throw out #'s as smoke...
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General-purpose HDR does not use masks, in fact "true" HDR (think Radiance and OpenEXR files, not the crap on Flickr tagged "HDR") does not discard any of the data until the image is tonemapped into an LDR image (which also does not involve masking).
That said, the K-7 uses an interesting type of exposure "blending" to create its "HDR capture mode" output images (which, again, are LDR not HDR), and these may have masks based on the exposure, contrast, and saturation of individual pixels or small groups of them. Ah, but it isn't HDR ouput, nor is it an HDR image that has been tonemapped. It's 3 exposures that have been blended together based on these varying criteria, with a function name that (apparently) confuses things further. So I guess you could say you are right when using the misnomer that Pentax has applied to the process.
If I sound grumpy, it's because I agree with this guy (who, like me, isn't new to this and isn't on Flickr):
Flickr HDR