Mike Chaney's Tech Corner

Hi folks,

 I recently replaced my Epson R2000, which had died, with a Canon Pro 100 (thanks for all the good advice, Fred!). I am very happy with it so far.

I have a question about the Qimage setup, however. I had been setting up the Qimage screen as shown in the attached image, grey skin. But I notice that Fred's settings, which he uploaded to another thread (black skin) are different. Can someone please explain to me the advantages of using Fred's over mine? These terms-- perceptual and relative colorimetric-- are not clear to me. Should I default to Fred's?

Thanks!

Liz

Hi again Liz. The setting I use, Relative Colorimetric, is not due to the Canon printer, but for color print accuracy.
It has to do with rendering and the Perceptual will change the shades of colors to pull them into the color gamut of the paper and the printer. It does that with the entire image colors' Perceptula pulls all the colors.
Relative Colorimetric says, "Hey, I sent you this red, and that is what I want. If a shade is not printable then it's OK. If it finds a shade slightly out of gamut, it will pull that one back in. NOT ALL colors, just the small shade that is out  of gamut.
I find that my prints match the original profiled image with my camera profile.
Hope this helps.
Fred
PS Maybe Mike can be more on point if he has time.

Thanks Fred, but I don't get it!

Liz

This may be of help
https://www.cambridgeincolour.com/tutorials/color-space-conversion.htm (https://www.cambridgeincolour.com/tutorials/color-space-conversion.htm)
Terry

LIZ
This helpful link from Terry is precisely what I was trying to say, and with the same conclusion: more accurate color.

PERCEPTUAL & RELATIVE COLORIMETRIC INTENT

Perceptual and relative colorimetric rendering are probably the most useful conversion types for digital photography. Each places a different priority on how they render colors within the gamut mismatch region. Relative colorimetric maintains a near exact relationship between in gamut colors, even if this clips out of gamut colors. In contrast, perceptual rendering tries to also preserve some relationship between out of gamut colors, even if this results in inaccuracies for in gamut colors. The following example demonstrates an extreme case for an image within a 1-D black-magenta color space:

Fred

Thank you Fred and Terry! I had actually done some Googling so I had read articles like this, but I find the language a bit arcane. For me the underlying question becomes, how would I know if any colors in my image were out of gamut? I don't know where the gamut starts and ends!

I will probably have to bite the bullet and do some test images.

Also--re: black point compensation. I see Fred ticks that, and I never had. Is that considered the default thing to do? (As you can see, I am looking for the best "defaults"!).

Thanks again.

Liz

Hi Liz,
You wouldn't normally worry about it because Color Management takes care of it.
Terry

OK, so that being said, should I use Relative or Perceptual for printing my photos? Or is it irrelevant?

It certainly is not irrelevant. I would use the Relative Colorimetric as I want color management to give me the most accurate color rendition. From Camera RAW shown on screen using my Camera profile color space, to the printer profile made specifically for my paoer and printer and ink, to the printer itself with the least adjustment by the rendering intent. I want little if nothing to be altered.
Fred
 

Let's try an analogy.  We have two painters with initials P (for Perceptual) and RC (for Relative Colorimetric).  Both of these painters (P and RC) have the exact same paints (inks) to work with when they try to paint your photo.  Let's see how they make USE of those paints:

RC: RC is the technical painter.  He likes to be as accurate as possible.  He arranges his paint palette so that if he sees a certain shade of green for the grass in your photo, when he dips his brush into that color in his palette, the color green that is painted is an exact match to the green of the grass in your photo.  When he gets to a bright yellow flower, however, he is able to dip his brush in the correct shades of yellow for part of the flower but the brightest shades of yellow in the flower are brighter than the brightest yellow paint he has (they are out of gamut).  What does he do in those areas?  He might add a little white to his brightest yellow, or add a tinge of green in order to get some detail there.  When he is done, the whole painting has accurate color except for those out of gamut areas: only those out of gamut areas are "faked" with different shades or brightness to try to make them look reasonable.

P: P is the artistic painter.  She doesn't care about accuracy because she wants the whole painting to look smooth and "fit" within the colors of her paint palette.  So she waters down all of the duller colors in her palette, leaving the bright colors alone.  Then when she paints, there is a wider separation between the less saturated colors and the more saturated ones.  None of the colors in her final painting are accurate, but if she runs into a bright yellow flower like RC did above, she can paint a yellow that looks brighter than it is due to the rest of the painting being "watered down": she still can't paint the correct/accurate yellow but it'll look like a brighter yellow than RC painted above.  And the "watered down" painting still looks OK because the eyes adjust for the lower contrast.  Further, if that bright yellow flower is the focus of the painting, her version may look better than RC's above!

Final word: I like RC.  Why?  Because I know that RC will put down accurate color for every color that my inkset can render: it's only "off" for the colors that are out of gamut.  And even more important, a lot of my photos may not have any out of gamut colors in my main subject: in these cases, the whole picture is accurate WRT color.  With P, none of your colors will be accurate and more importantly, even if your photo contains no out of gamut colors, they still won't be accurate with P: they'll be watered down.  That's because P waters everything down by the same amount, regardless of what your photo looks like, just "in case" you run into very bright colors that are out of gamut.  So in a sense, P is overkill for most photos and may make them look dull.  BUT, it's there in rare cases where you may have a very bright yellow flower or maybe a shiny red fire engine that you want to "pop" with respect to the rest of the photo.

Best I can do...
Mike

Mike, this is fabulous! I get it!

Thanks so much!

Liz

Don't forget the out-of-gamut check, which I find quite useful. Use your soft proof button at the bottom, then check the gmt box to highlight the out-of-gamut areas.

Perfect.. Good idea. I was actually making  some screen snaps for you and I actually printed the twi images side by side. I used the special COLOR MANAGEMENT setting where I placed two copies of an image and set one to Perceptual and the other Rel Colorimetric and then used the softproof and gamut box.
This is important!!!!    The gamut is based on the paper you chose. My Matte paper shows a wow. Out of gamut areas
The semi gloss very close.
The actual prints both on the same page are acceptable, with the clear winner being Relative Colorimetric.

Fred
 

I did not know anything about this! Must pursue...

Wow, I never noticed that soft proofing option! (You can see that I am learning as I go along--ten+ years later.) Thanks for this useful bit of information, CHoffman!

What surprises me a little is that dark areas, as well as bright colours show as out of gamut.
Terry

The ugly one  is the profile for the cheap matte paper.  Percep and Rel C  Gamut is smaller
The good looking one is Ultra Luster profile with REL  C   intent and Perc
Fred

Old guy stories- Back in my darkroom days, black and white paper came in a plethora of surface finishes. Everything from sandpaper-like and canvas-like, to the well known glossy "F" surface that could be dried to a mirror-like finish on chrome plates. The maximum tonal range was always with the glossy finish because the blacks were blacker. Any other finish scatters light and the black isn't as black. If the paper used an off-white base, usually cream colored, that reduced tonal range even more. A canvas paper with a warm cream colored base was great for portraits and large prints, but a poor choice for most other things. My technical knowledge of color isn't as good, but no doubt saturation is affected the same way. Matte and many "fine art" papers won't produce the gamut range that a high gloss paper will. OTOH, it's horses for courses and you choose the paper for the effect you want, just being aware there are always trade-offs.  8)

To continue this very helpful thread just a bit more, does anyone use Photo Lab Elite 3 as their processing software to then send to Qimage for printing?
Having a bit of a conundrum on the settings and would appreciate some guidance. Thanks.

One of the better explainations I have read. Thanks!