On 9/4/2013 2:35 PM, Matthew Hunt wrote:
On Wed, Sep 4, 2013 at 2:22 PM, Igor Roshchin <s...@komkon.org> wrote:
I have a question for John Sessoms:
John, you wrote for your photo:
"This is not an HDR image. It is a blend of 4 exposures 2 sec to 45 sec
using layer masks & blend modes."
How is it different from HDR?
I would say that the difference is that in "HDR imaging" (as the term
is generally used) at some point (prior to tone-mapping) you produce a
scene-referred high-dynamic-range image. This requires understanding
or measuring the quantitative exposure relationship between the input
LDR images, allowing the software to know (for example) that a bright
point in the HDR image is 1,000,000 times brighter in the original
scene than a darker point.
What John did is more akin to exposure fusion, as performed by the
Enfuse software for example (although it sounds like John blended
images manually). In exposure fusion, the pixels in the output image
are a weighted average of the pixels in the input image (with weights
varying from pixel to pixel), but exposure fusion algorithms don't
need to know the quantitative relationships between the exposures...
they can just prefer to weight pixels that are "well exposed" (i.e.
near the middle of the LDR exposure range).
What I was trying to do was something I could do years ago with
Cibachrome, where I could combine two or more slides by making masks.
The mask would only allow light from the part of the slide image I
wanted in the final print to reach the paper, blocking the rest.
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