In Lightroom, it depends on which conversion algorithm you are using
too. You can choose from the legacy ACR engine or the newer
RawShooter-based engine. They do render things differently. Of course,
there is the DCRAW based converters...
Highlight recovery is an interesting animal. Over the past few months
I've been really digging down into it trying to figure out what is
going on as well as trying to figure out why the in-camera converters
lose this headroom. Turns out that in every camera I've
tested--including the 5D, 7D, D2X and my cameras, the in-camera
converter clips right at the point where color integrity fails. When
we perform highlight recovery, we lose color integrity.
What essentially is going on is that the three (or four) sensels used
in the Bayer conversion do not clip at the same point. Especially when
working in an environment where we are in an off white-balance. A
derived 100% "white" is 254.254.254 but a derived 100% red is 254.0.0
and a derived blue is 0.254.0 and a derived green is 0.0.254. A
derived 100% magenta is 254.0.254.
Where things get really fuzzy, though, is when we work with the
derived colors of magenta, cyan and yellow. The way these colors are
mixed together requires that all sensels clip at the same point. If
they don't, these three colors will shift when performing a highlight
recovery. More often than not ACR will just turn it to gray. With most
details we don't really notice because there are other pixels
intermingled within that recovered area that provide color to the
image.
In regards to monochrome images, highlight recovery is just
fine--highly desirable, in fact. This recovery does give us another
stop to work with. But when working with color images the last stop of
recovered highlights are rarely correct. The camera manufacturers just
clip these off and thereby keep the color integrity intact.
Why wouldn't the sensels all clip at the same time? They would if you
are shooting only at the native WB of the sensor.
AG
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