Alan Browne wrote:
On 2012-07-21 23:20 , Trevor wrote:
"Bruce" wrote in message
...
The Panasonic G5 also has very good dynamic range, approximately 12
stops between ISO 160-400. I think the OM-D is probably a stop
better, which will unfortunately overshadow the G5's excellent
performance.
Of course most m4/3 users will never obtain anywhere near these
figures because they don't shoot RAW. Shooting JPEGs yields a dynamic
range that is 1-2 stops less.
How is an 8 bit file "1-2 stops less" than a 12-13 bit one?
A good JPG doesn't "lose" dynamic range because of the number of bits,
Yes it does. A generic 8 bit gamma corrected image will
not have more than about 11 stops of dynamic range.
That is less than the typical 12 to 14 that cameras
today can produce.
Of course JPEG does, as you say, do other things. The
total effect of the JPEG format results in a dynamic
range of about 9.6 stops, by design.
it is a log compressed format and as such can potentially represent the
full DR of an image - it does lose fine dynamic resolution, of course.
I have no idea what "fine dynamic resolution" is
supposed to be. But an 8 bit gamma corrected image
cannot support the "full DR" that most cameras can now
produce.
It can support more DR than either a good monitor or a
good print can produce, which is the significant point!
It was purposely designed to have just more than enough
DR for that. A JPEG can be adjusted up or down by a
stop or less, because it has about that much more than a
typical display mechanism can show.
Where JPG does lose DR is when it maps to a colorspace. JPG's created
in camera are mapped to a colorspace (and most cameras provide at least
a few choices). Such colorspaces have comparatively narrower DR.
There's more to it than that, but that is a part of it.
Of course there are colorspaces that are wide enough,
but it makes no difference because JPEG can't actually
record them with fine tonal divisions and neither can a
monitor or a print.
--
Floyd L. Davidson http://www.apaflo.com/
Ukpeagvik (Barrow, Alaska)