"Ekta Space PS 5, J. Holmes"

Joseph Holmes, jh@josephholmes.com   6/2/98, updated 3/31/99

This is a matrix type and simple gamma curve type profile which is a
variant on my original Ektachrome Space, J. Holmes profile that I use as my
own archiving space, which is different so as to make it compatible with
the architecture of Photoshop 5.  When the PS5 profile is used as the RGB
working space in Photoshop 5, it gives the same color and tonal qualities
as when used with ColorSync in any other application.  This is not the case
with my original and otherwise preferred Ektachrome Space profile.  Nor
would it be the case with any scanner profile, for instance.

Ekta Space PS5, J. Holmes is a special RGB color space profile which I
designed for high quality storage of image data from scans of
transparencies without any clamping of data when the colors are moved
through a scanner profile into Lab, and thence from Lab into this profile
(although in actuality the colors move directly from the scanner space to
this space when a conversion is done).  This first transformation should
always be done with 16-bit per channel information if at all possible.
That way you wind up with flawless information and only one further
transformation need ever be done to your image data--from the RGB storage
(working) space to the output device space, minimizing any chance of having
too few levels for optimal tonality in any given output.

This profile's chromaticities are chosen specifically to totally protect
(just barely) all the colors present in an Ektachrome IT8 target, which
includes 36 points representatively sampled from the skin of the Ektachrome
film family gamut.  Only a very small bit (about 2%) of the most saturated
darker cyans of a Fujichrome will be smashed inward and become the same in
chroma as the slightly less saturated darker cyans when stored in this
color space.  The smashing of color that would occur with storage of either
of the Ektachrome or Fujichrome color spaces into any monitor profile, or
even into a color space such as Adobe RGB (1998) or Bruce RGB is vastly
greater, although if any given image has no saturated colors, this
consideration is irrelevant.  The profile might also therefore have been
called "Ektachrome & Fujichrome Space".  The gamut of Agfachrome is very
similar.  I don't know the Kodachrome gamut but it is unlikely to be quite
different.

This smashing of color may, at first thought, seem inconsequential, given
that few printers have gamuts that allow them to show many of such smashed
colors as they would have been before smashing (more intensely colorful
mostly), BUT the way in which these out-of-typical-printer gamut colors are
brought into gamut is important.  When smashed into an RGB storage
(working) space (because it is too small to hold them all), the data is
simply clamped in a way that typically causes hue shifts and a complete
lack of chroma differentiation between the smashed colors and the nearest
in-gamut colors.  If however, you leave this smashing of colors to the
printer profile (as it would be when you take colors stored in "Ekta Space
PS5, J. Holmes" and transform them into the final printer space using the
printer profile's perceptual rendering intent table, the gamut mapping is
done much more intelligently and with more delicacy than the alternative
meat-axe approach.  This will help to preserve tone and color gradients in
such saturated colors in the final print.  If your original image has no
saturated colors, then any RGB space such as a typical monitor profile is
likely to safely contain all the colors.  Only your own experiments can
teach you about this in detail (i.e. give you a feeling for how saturated a
color has to be to be outside of which gamut).

To clarify: once colors are mapped inward for storage in a smaller gamut,
they are almost certain to never be re-mapped back out to where they used
to be, recreating their original relationships.  Ordinarily such rebuilding
is impossible and not part of what goes on in Color Management.

This profile has chromaticities which are extremely close to those in the
"Ektachrome Space, J. Holmes" profile that I use as my archive's master
profile.

This "Ekta Space PS5, J. Holmes" profile has a gamma of 2.2 and this tone
curve is the greatest difference between it and the original, Lut 8 type
profile, which has an "arbitrary" tone curve that is a closer match to the
natural tone curve of some printers (e.g. the LightJet 5000).

This profile will function inside of Photoshop as the RGB space profile, or
PS 5 can copy it and make its own.  Because this profile is a matrix/simple
gamma type profile, when Photoshop does copy it, the copy will be identical
in function to the original profile.  This would not be the case if
Photoshop copied a profile with an arbitrary tone curve.  Photoshop would
"simplify" the tone curve into a simple gamma curve.

Complicated method:

To make Photoshop copy the profile for use as an RGB working space in PS5,
first select this profile as your System Profile in the ColorSync control
panel (ColorSync 2.5 or later).  Then open up FileColor SettingsRGB Setup
in Photoshop and see that the profile has appeared as the monitor profile
identified in the lower part of the dialog box.  Then choose "Monitor RGB"
as the working space in the "RGB" pop-up at the top of the dialog box.  See
how the chromaticities, gamma and white point of the Ekta Space PS5 profile
are displayed as attributes of the color space thus selected: Gamma 2.2,
5000K, Custom.  Now select SAVE, and save the profile as an Adobe ICC
profile, e.g. into the Adobe Photoshop Settings folder in the Photoshop 5
folder, or into the ColorSync profiles folder, depending on which you think
you may find easier to navigate to later, when you need to find it to
re-load it after having used a different working space.  Close the dialog
box.

Now go back to the ColorSync control panel and re-select your favorite
monitor profile that is right for your calibrated state.  Then re-open the
RGB Setup dialog and check to be sure that the correct profile is now shown
as your monitor profile below, and finally, select Load to find the saved
Ekta Space PS5 profile back in as the working space, since we had been set
to monitor space before.  Any time you want to change working spaces, just
select one from the list OR pick Load and go and find the profile that
describes the working space you want.

OR (a much simpler way)

Simply open the RGB Setup dialog in PS5, select Load, and navigate to the
profile, wherever you put it, and choose it for loading.  Now your working
space is set to the profile you loaded.  If you select an RGB profile as
the working space which is NOT a simple gamma curve and simple matrix type
profile (e.g. a scanner profile, or a LUT type monitor or color space
profile), Photoshop will "simplify" it by changing the tone curve to the
closest gamma curve and by building a matrix type profile, in effect, from
the chromaticities in the original profile.  This creation of a gamma curve
substitute for the original tone curve may change the tone curve
considerably from what it was in the profile thus selected.  Therefore only
choose profiles as RGB working spaces which are the simple gamma curve and
simple matrix type, so that the nature of the working space will not differ
from what you expect it to be from having worked with it other applications.

This is why when one selects Monitor as the working space in Photoshop 5,
if the System Profile happens to be a LookUp Table type monitor profile,
e.g., the listing in the RGB working space pop-up will say "Simplified
Monitor RGB" instead of just "Monitor RGB".

I have chosen the gamma of 2.2 partly on account of a recommendation of 2.2
as the most linear gamma.  My experience would indicate that that is in the
ballpark.  (further experiments have indicated that the range of 2.0 to 2.2
yields equivalent results, 2.2 favoring the Fujix, for example, and 2.0
favoring the LightJet).

This is a quickie version that I expect to stand the test of time.  It was
far easier to make than the original profile for purely technical reasons,
and because the major decisions had already been made in the design and
experimentation period of more than one hundred hours for the original
profile, "Ektachrome Space, J. Holmes".

Good luck and may good color be upon you!