Datacolor User to User Support Group.

On Dec 12, 2007, at 9:11 AM, harleyandhiggins wrote:

> Using PrintFixPro Suite, version 3 Prinefix
>
> Canon iPF-5100
>
> Profiled papers:
> Epson Luster
> Kodak Ultima Gloss
>
> Here are my observations.
>
> In both cases, the printed colour targets are bright and realistic
> looking.
>
> When comparing the split targets on-screen, when there is a visual
> difference, the measured are alway darker/duller in appearance.
>
>
That's how it should be. This will always be the case. In the
split view, the upper left corner colors are "pure" RGB colors
which exist simply to show you the RGB representation of each
patch. Printed colors are going to be different (even if the
target was printed through a profile with color management).

Paper white, as measured, will never be a "perfect" RGB white;
it will always (if measured properly) display as a light gray,
usually with a slight color cast.

Black (the first patch in every target) will always "appear"
lighter than a perfect RGB black in measurements; more so on
matte papers.
> On the Epson paper, the on-screen split screen differences are
> signficantly less than the Kodak. Also, more numerous on the Kodak
> split screen.
>
> In both cases, the colours are ALWAYS darker/duller. The differences
> are much more numerous and more significant on the Kodak paper.
>
> Generally speaking, what does this indicate?
>
>
More than anything: that the Epson paper probably has a wider
gamut than the Kodak.

It's less confusing to toggle the Target window display between
Pure and Measured, rather than looking at the Split view. What
you see, in the Measured display, is the measured gamut of the printer;
-everything- that it can print, with your driver settings (paper/media
type, output quality/speed/resolution, etc. and color management
disabled) falls into what you see here. It can't print darker blacks,
it can't print more saturated primaries, etc. Look at the "corners"
of first 5x5 cluster in the 225 patch target, and you'll find the
"pure" black, blue, cyan, and green patches on the corners. That's the
best your printer can do. Look at the corners of the 5x5 cluster that
has the paper white patch, and you'll find the "pure" magenta, red,
and yellow patches, along with the paper white (no ink). Again, that's
the best your printer can do. No amount of profiling can change that.
Your only controls over changing these "best case" starting points
for the "corners" of color space in RGB are the driver controls for
paper/media type, output quality, etc. and the color management controls
in the driver (which should be turned off).
> When I printed the pic of the beige home with lots of blue sky on the
> Epson paper, there was noticable banding only in the beige area of
> the home. Would profiling with the 700 patch correct this?
>
>
Yes, it would, if the banding is a result of non-linearity in the  
printer
on this paper that's not being addressed well enough by the 225 patch
target.

However: if the banding is coming from errors in the measurements, then
it would be better to fix them by checking the 225 patch (and extended
grays, if you've done them) measurements for problems, rather than by
printing out the 729 patches and "accidentally" fixing the banding by
using a larger measurement set that doesn't have any errors.

To check your measurements: Look at them in Measured mode in the Target
window, and look for inconsistencies, such as: patches which are visibly
lighter or less saturated than their neighbors; patches where you can  
see
that the hue has shifted incorrectly with respect to the neighbors. If
you toggle the Target window between Pure and Measured, what you should
see for the first 5 "clusters" of 5x5 patches is an overall darkening
effect, but you shouldn't see any of the patches "pop" to a different
hue, lightness, or saturation when looking at them in context of their
neighbors. It's easy to see this in those first 5 groups because they're
arranged in a pattern of color steps that span RGB space in equal
increments. In the other patches in the target, which are scattered more
at random, it's harder to see errors this way, but usually an incorrect
measurement in the shadows (too light) will stand out easily enough.

if you see any bad measurements, remeasure over the patch, or sequence
of patches, in the Target window; you should see the fixed changes fall
into place.

Other possibilities that people tend to get wrong:

- Not calibrating the spectro on the calibration base. This still comes
up, even in the latest two versions of software (2.1 and 3.0), in which
we added the picture of the spectro being physically put onto the base,
with a red arrow pointing right at the tile. There are still support
tickets as recently as this week in which people were calibrating the
spectro on the paper, rather than on the tile...! If this is done the
wrong way, the overall measurements won't look bad, but they'll be wrong
enough to throw everything off, induce color casts, and make prints that
are generally unacceptable.

- Printing targets and/or prints (after building a profile) with head
clogs. If you're not getting full inks printed through your nozzles when
you print a target, you will never get good results, and the only way
to ever "fix" this kind of problem is to throw away the target prints  
and
measurements and to start over. There was a support ticket last week
from someone with a Canon 9500; and BOTH of these problems existed:  
first,
that the spectro wasn't calibrated on the base (on the round, white,  
dime-
sized plastic calibration tile); and -then-, that there was a head clog,
which was only apparent once I very carefully looked at the  
measurements -
some of the cyan was missing, and so there was a "banding" of color
in the steps of blue in the target print, resulting in some of the 5- 
long
patch measurement sequences being duplicated. The only way to fix this
was to do a head cleaning (even though the nozzle check didn't show an
obvious problem!) and to start over. Now the prints done from fresh
measurements are beautiful.

Best regards,


David Miller
Senior Software Developer, Digital Color Solutions
Colorvision