Datacolor User to User Support Group.

Here's a primer on rendering intents by IBM:

"
Rendering intents
Rendering intents indicate what you want a printer to do with colors that
are outside its gamut.

ICC profiles support these rendering intents:

  a.. Perceptual
  If an image includes any colors that are out-of-gamut for the printer, the
printer adjusts all the colors in the image, even those that are already in
the gamut of the printer, so they are all in-gamut and maintain their color
relationships to each other. The result is an image that is visually
pleasing, but is not colorimetrically accurate. The perceptual rendering
intent is useful for general reproduction of images, particularly
photographs.

  b.. Saturation
  If a print job includes colors that are out-of-gamut for the printer, the
printer replaces the out-of-gamut color with the nearest color in the gamut.
It also adjusts the in-gamut colors so that they are more vivid. Saturation
is the least used rendering intent, but it is useful for business graphics,
such as images that contain charts or diagrams.

  c.. Media-relative colorimetric
  If a print job includes colors that are out-of-gamut for the printer, the
printer substitutes the nearest in-gamut color; in-gamut colors are not
adjusted. Colors printed on papers with different media white points might
not match visually. The media white point is the color of the paper that the
print job is printed on. For example, if you print an image on white paper,
on off-white paper, and on blue paper using the media-relative colorimetric
rendering intent, the printer uses the same amount of ink or toner for each
one and the resulting color is technically the same. However, the images
might seem different because your eyes adjust to the color of the background
and interpret the color differently. This rendering intent is typically used
for vector graphics.

  d.. Absolute colorimetric
  All colors are mapped using the same method as the media-relative
colorimetric rendering intent, however, all colors are adjusted for the
media white point. For example, if you print an image on white paper, on
off-white paper, and on blue paper using the media-relative colorimetric
rendering intent, the printer adjusts the ink or toner used for each one.
The resulting color is technically not same, but the images might look the
same because of the way your eyes interpret them in relationship to the
color of the paper. The absolute colorimetric rendering intent is typically
used for logos.


  a.. Related concepts
  b.. Gamut and rendering intent
  Every device has a gamut, a range of colors or shades of colors that it
can display or print. Some devices have larger gamuts than others; some
devices have gamuts that are similar sizes, but that contain slightly
different colors. When an image or a print job is created on a device with a
gamut that is different from the printer, you can use a rendering intent to
tell the printer how to adjust the colors that are outside the gamut of the
printer."
Source:
http://publib.boulder.ibm.com/infocenter/printer/v1r1/index.jsp?topic=/com.i
bm.printers.plngcfgguideyuma/g6apcmst181.htm

pjs
"Light makes photography. Embrace light. Admire it.
Love it. But above all, know light.
Know it for all you are worth,
and you will know the key to photography."
George Eastman

-----Original Message-----
From: Myron Gochnauer
Subject: [colorvision_group] Re: Why "Saturation" for rendering intent w.
Spyder3Print?


  I think I simply do not understand with these "Intents" do. I've been
using Saturation Intent for ordinary scenic photography and portraits, which
call for subtle colors and transitions, unlike "charts and graphs" that
Adobe says Saturation is good for.  And my results are, it seems, very good.