Why do we even need to bother profiling a camera given that the
reviews of these new all-singing-all-dancing cameras would have us
believe that their colour accuracy is nothing short of perfection?
Any owner of the original and very popular Nikon D1 digital will
give you plenty of reasons, likewise owners of just about every
other digital camera on the market. I own both a Canon EOS D30 and
a Nikon CoolPix 950, and there are occasions when certain colours
as captured by the camera are quite simply nowhere near the real
colours. It should also be noted that the Nikon and Canon Digital
SLR's are not unique in having difficulty rendering some colours
accurately, the phenomena effects every digital camera in one way
or another.
Over recent months I've been fortunate to evaluate a
number of software packages designed specifically for the purpose
of profiling digital cameras. I've also tried a few were the
vendor still uses the IT8 target. So far as the latter type goes
they are a waste of time, effort and money. Profiling a digital
camera requires a completely different type of target to that
designed for scanner profiling.
Digital cameras capture colour information from many different
types of material and so the IT8 target with its target patches
based upon only three colourants is virtually useless. The colours
of the Macbeth ColorChecker and Macbeth
ColorChecker DC charts have properties whereby the colourants used
have the reflectance spectra similar to real world objects such as
skin, foliage, etc. and so will replicate their response under a
wide range of lighting conditions. Likewise the neutral patches,
which have a relatively flat reflectance spectra and thus remain
neutral under virtually any lighting conditions.
Nevertheless and contrary to what some would have us believe;
digital camera profile and editing software is not all created
equally, nor is it foolproof. The quality of the resulting profiles isn't
simply a matter of the software being used. The choice of target;
i.e. Macbeth ColorChecker or Macbeth
ColorChecker DC, and the lighting conditions under which it
is captured will all play a part in the quality of final profiles.
Don't assume that the more expensive ColorChecker DC chart will
always be better, it won't, and don't assume that all digital
cameras are equally easy/difficult to profile, they aren't. For
many the time, effort and expense of creating custom profiles for
their digital cameras is just not worth it. For others it isn't a
subject open to discussion it's something they have no choice but to
do. Hopefully the above discussion and following review will go someway to helping
the reader better
understand the reasons behind, and the processes involved.
Depending upon the actual target used it's now simply a matter
of selecting the target image file, choosing the matching
reference file and cropping the target image so that it fills the frame.
GretagMacbeth ColorChecker Chart
The above screenshot shows the less expensive Macbeth
ColorChecker chart (approximately $60), which comprises 6
greyscale tones and 18 coloured patches. As discussed above, many of the patches
represent natural objects of special interest such as: skin tones,
foliage and blue sky. Macbeth describe the target patches as
follows: "The squares are not only the same colour as
their natural world counterparts, but also reflect light in the same way in all
parts of the visible spectrum".
GretagMacbeth ColorChecker DC Chart
The screenshot show above demonstrates the feature whereby
inCamera Professional can be
configured to ignore the eight glossy coloured patches of the Macbeth
ColorChecker DC chart. In theory, the inclusion of these patches
helps the profiling software determine how the camera behaves when
capturing more saturated colours. The reality is that these patches
can actually result in a less than optimal profile for no other reason
than reflections are almost impossible to avoid. On those occasions that I did
manage to capture a reflection free image of the target there was no
doubt as to the improvement in the quality of the profile, but such occasions
were extremely rare. A quick check of forums such as the "ColorSync" and
"Colour Theory" mailing lists confirms that the glossy patches are the
single most likely reason for failure when profiling a digital camera.
Pictographics are to be congratulated for enabling the user to
avoid them, although it is always wise to check the quality of the
profile with them included.
To assist in getting the most accurate crop of the
target image the user should mouse click each of the corners, in
turn, whilst holding down the Option/Alt key. This activates the
Zoom box Once the target image has been cropped it's simply a
matter of pressing the Save button; creation of the profile will be
almost instantaneous. Note: at
this point the profile has been saved in Pictographics proprietary (.Prof)
format and so we must do a little more work before our task is
complete.
Contd. on next page...
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ictographics
