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Date: Sun, 12 Jun 2005 16:22:12 GMT
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Xref: number1.nntp.dca.giganews.com comp.sys.mac.graphics:48614 comp.sys.mac.hardware.misc:185095 comp.sys.mac.misc:246303 comp.sys.mac.portables:167822 comp.sys.mac.system:597997
James L. Ryan wrote:
> Today I had the opportunity to the same set of pictures with some dozen
> digital cameras of varying makes and sophistication. What I found interesting
> is that the on-screen images from these cameras varied significantly in terms
> of how the colors of common objects appeared on screen and when printed. Is
> there a way to calibrate things so that this difference in coloration is
> eliminated?
Note Followup-To: comp.sys.mac.graphics
Possibly, depending on why you are getting the current
differences. I suspect that you used a common application to
import all of the images (e.g., Image Capture). How was it set up
to attach an appropriate ICC (colorsync) profile? Usually, most
digital cameras are built to use the generic sRGB profile but
none of them match it exactly. Some cameras that don't match the
sRGB well will come with a software disk containing their own
profiles. If you don't attach those profiles to the imported
images, they will display incorrectly and will map to a printer
incorrectly. By default, most image importing apps will not
attach ANY profile so the image will look different in each
application it is used in depending on how that application
treats images with no profiles. BTW, I suspect that this is
likely part of your problem. Either no profile is being attached,
the wrong profile is being attached, or something is modifying
the profile the images have (e.g., iPhoto has this nasty habit of
changing the profile on an image when it is edited defying color
management rules. Apple has never gotten around to fixing this
much to the aggravation of many amatuer photographers that would
like to use the image editing capabilities of iPhoto)
As I mentioned above, the sRGB is common to many cameras but it
is only a generic profile and although the differences may be
slight, each camera is different (even for the same type and
model of camera). It is possible to "calibrate" a camera using
special software and test images. You take a picture of a special
test image under tightly controlled lighting conditions. That
image is then imported WITHOUT profile attachment and analyzed by
the profiling software. The Profiling software can then create a
new colorsync profile for the camera which can then be used when
importing images taken on that camera.
One last item. The technologies used in different cameras can
produce different color saturation capabilities for the same
scene. The sRGB profile can limit some of higher saturation
colors produced by the camera. This may be ok if only viewing on
a display or a web site, but can limit the picture some when
sending to a printer. If the camera has a natural color gamut
that is wider than the sRGB profile allows, using a different (or
custom) profile for the camera can sometimes allow a little more
saturation to make it to the printer.
Anyway, for the OP's situation, although different cameras will
produce pictures that can vary, a step toward more consistant
images between cameras (where differences should not be
appearing) would be to ensure that all images imported from the
camera are being tagged with the appropriate color profile for
that camera. Then ensure that all color-aware applications that
are using the image have their color management turned on (i.e.,
if it is configurable) so that the profile on the image is used
properly.
Some of the above is a little simplistic but I hope it gives you
some ideas of what may be happening.
--
Jeff Wiseman
to reply, just remove ALLTHESPAM
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