Introduction and discussion
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
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.
So how do we go about creating an ICC profile for our typical
digital camera sing inCamera Professional?
The procedure is fairly straight forward and to a large extent
requires little or no previous experience. The steps are as
White balance the camera using a Kodak Gray Card. The
process is usually described in the camera user manual.
Determine the exposure for the scene (lighting falling on
target). Typically can mean anything up to 1/2 fstop
or more above the metered exposure when measuring off the
Kodak gray card. It's probably best to capture a series of images
at different exposure values above and below the gray card
Take a picture of a Macbeth ColorChecker or ColorChecker
DC chart. It's important that the whole chart is included
and that it's evenly illuminated and free from reflections.
All camera automatic exposure features should be set to
Transfer the images to the computer and Open inCamera
Professional and choose New>Digital Camera
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
Once a profile for the digital camera has been created it
is always a good idea to check how it behaves. The screen shot below
shows a results for a profile based upon a Canon EOS D30 capture of the
Macbeth ColorChecker DC chart. The information contained in this
example goes well beyond the simple graphical comparison of the chart
that is provided by most other profile software vendors.
With inCamera Professional
the tones and colour characteristic's of each and every patch are
compared against the reference values and the patch with greatest error
is highlighted. In this case it is one of the white patches (J6), and it
can be seen that the error is quite small at a "Delta-E of 0.5".
The overall colour difference is even smaller at a "Delta-E of 0.1"
Run your mouse across any coloured patch and the input data for the
profile and its reference value will be displayed.
Note: Delta-E is a measure of colour
difference in CIE Lab. Under ideal viewing conditions a
Delta-E of 1 represents a just perceptible colour
difference to the human eye although in less than ideal lighting values
of between 2 or 3 can be considered as equivalent.
It's also possible to measure the amount of noise found
in the captured image. Again in the example shown above (Canon EOS D30 in
linear raw mode) the values are quite low. Although not shown here it is
possible to represent the actual noise levels within the image using a
graphical overlay. This will show a coloured dot over each patch that
exceeds the specified level of noise.
We can also review the overall uniformity of the lighting
conditions under which the original target image was captured. This
feature is only available when using the Macbeth ColorChecker DC
chart. The uniformity of lighting appears to have quite a large impact
upon the quality of the resulting profile and being able to check it
helps considerably in determining whether it is better to simply retake
the photograph again or depend upon simple editing of the profile.
Exporting the Profile
Once the user is happy that the profile has been created
it's simply a matter of Selecting the Export command. Again, inCamera
Professional offers a wider range of options for saving an ICC
The profile can be saved in either 8-bit or
16-bit precision, Tonal Compression technique and the if these
are not enough the user can also choose the Rendering Intent.
There are a number of other choices for adaptation (e.g. XYZ Scaling or
Bradford Transform) to be found under the Options button. I
recommend that you choose XYZ scaling as it is more compatible with Mac
and PC appications. Again on-line help is available for quick reference
and the comprehensive user manual should also provide more than ample
guidance. Speaking of the user manual, this is a mine of information and
the fact that it can be downloaded, for free, from the
web site should not be ignored.
Ideally you should try the profile on a range of images
prior to deciding if any edits may be required. Typically the image will
appear somewhat flatter (less contrasty) than you would normally expect,
however, this is easily corrected using a very simple S-curve in
Photoshop. If you feel the need for further guidance on the operation of
inCamera Professional Pictographics
provide a number of tutorials on their web site
For those occasions when you find the newly created
profile isn't quite accurate enough the profile editor provided with
inCamera Professional is available. It
is both powerful and easy to use. The user has the ability correct for
tonal and colour discrepancies within the profile along with hue,
saturation and brightness. A question often asked of ICC profile software
is - why would we need to edit the profiles? In the case of digital
camera profiles it could something as simple as poor white balancing when
capturing the target image or as is more likely uneven illumination.
Another possibility and one that impacted upon my trials is the fact that
neither the basic ColorChecker chart or the more expensive DC version has
any sample patches that exceed a Lab lightness channel value of 96. In a
gamma 2.2 working space Lab 96 for the lightness channel equates to
roughly RGB=244. This falls far short of pure white and can often lead to
really odd colour imbalances, especially when the sensor behaves in a
non-linear fashion at or near saturation (RGB=255) (e.g. the Canon EOS
D30 magenta whites when images are grossly overexposed).
inCamera Professional Profile
The above screenshot shows a before and after edit view
of the image with the profile edited to give a neutral colour balance.
call this method of removing global colour casts "Neutral Pointing".
With this example I had deliberately corrupted the highlight patches of
the target so that they were excessively red. In doing so I was trying to
replicate a problem I noted with only marginally overexposed images from
at least two high end digital cameras. Notice that the edited profile
corrects for the error without impacting upon the remaining tones. The
process of Neutral Pointing is very simple. The user simply
identifies areas of the image that should be neutral and clicks these
with the sample tool. For complex images it's best to use the scale
method as shown above. However, the inCamera
Professional profile editor also offers a method that is
similar in operation to the "Variations" tool in Photoshop for
those situations were finding neutral points is difficult.
As with the cropping feature described above it is
possible to zoom into a section of the image. Simply holding down the
Option/Alt key and clicking the relevant section of the image with
the mouse curser cause inCamera Professional
to zoom into that section of the image.
Occasionally a profile will have the effect of clipping
the white or black points of some images or it might even be the case
that some images were grossly underexposed or overexposed. Using the
Black and White point adjustments it is possible to modify the profile so
that the image data is spread more effectively.
Black and White Point Adjustment
As with global colour casts, making adjustments for hue
shifts that impact upon only one colour is fairly straight forward.
Pictographics have chosen to use the
Hue (colour) Ring as the basis for these edits.
Selective Colour Adjustments
As noted in the previous section it's probably best not
to make edits to a profile based upon only one image as doing so might
result in a profile that is image specific (not what we would normally
intend). I find that cycling through a range of different images helps
identify those hues that might need some refinement. The process of
editing a hue requires only that the user clicks the the appropriate hue
in an area of the image with the sample tool and then drags the anchor
point on the hue ring in the direction that fixes the problem. It's also
possible to increase/decrease the chroma (saturation) and Lightness of a
specific hue. So long as the appropriate monitor profile has been
selected in the inCamera Professional
setup procedure the display will be very accurate. An on-line Help
function is available via the "?" icon on the top right hand
corner of the editor panel.
is considerably more flexible and more accurate than the other
digicam profiling software products that I have evaluated up to date. The
ability to ignore the troublesome glossy patches of the Macbeth
ColorChecker DC chart is something that other vendors should consider
VERY seriously. The included profile editing tool with in-built
softproofing is much more than a simple profile tweaking tool since it
allows the user to exercise a great deal of control over how the profiles
will behave when applied to images. The inclusion of the editor sets
inCamera Professional apart from other
Whilst the results that I obtained from
inCamera Professional are very good
they are not perfect. That said inCamera
Professional succeeded were others had failed in so far as I
finally managed to produce high quality ICC profiles for the Canon EOS
D30 in its linear raw mode. Profiling any digital camera in its linear
condition is extremely difficult not least because the images are VERY
dark and never being anywhere near full-scale. Having learned a few
lessons along the way with inCamera Professional
I was able apply the same methodology with the other software
packages, although not always as successfully and NEVER with the
Macbeth ColorChecker DC chart, inCamera
Professional was uniquely successful in this regard due to its
ability to ignore the glossy patches.
In publishing this review I am conscious that there are
be many elements of the inCamera Professional
software package that I have not been able to cover in any detail. These
include the very powerful Monitor calibration and profiling tool and the
ability to import an edit digital camera ICC profiles from other vendors.