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Author Topic: Hahnemühle "black point compensation" off  (Read 8487 times)
paulbk
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« on: April 04, 2006, 05:40:12 PM »
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re: Black Point Compensation: Off

This from the Hahnemühle ICC-Profile site:
"Intent: Perceptual, Black Point Compensation: Off."

Go here Hahnemuehle
Scroll to bottom of page.

Has anyone used these settings with Epson driver (no RIP)? Results? Comments?
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paul b. kramarchyk
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alainbriot
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« Reply #1 on: April 04, 2006, 05:56:09 PM »
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re: Black Point Compensation: Off
This from the Hahnemühle ICC-Profile site:
"Intent: Perceptual, Black Point Compensation: Off."
[a href=\"index.php?act=findpost&pid=61818\"][{POST_SNAPBACK}][/a]

This is the standard approach when using Perceptual Intent. Black point compensation (BPC) is not checked during conversion because Perceptual is white point and black point relative.  

BPC must be check if using Relative Colorimetric (relcol) because relcol is white point relative and black point absolute.

The 2 other intents (saturation and absolute colorimetric) are not recommended for photographic printing.

Alain
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Alain Briot
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paulbk
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« Reply #2 on: April 04, 2006, 06:22:00 PM »
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Thank you very much Alain. I've always been told to leave BPC 'on', no matter what the rendering intent.

p
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paul b. kramarchyk
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alainbriot
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« Reply #3 on: April 04, 2006, 06:52:00 PM »
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Thank you very much Alain. I've always been told to leave BPC 'on', no matter what the rendering intent.
p
[a href=\"index.php?act=findpost&pid=61825\"][{POST_SNAPBACK}][/a]

Only with relcol.  Not necesary with perceptual.

It's not a very well understood aspect of color management which explains the many different opinions that are out there.  My current work focuses on color and that's why this is important to me.  Note that these settings are valid with both the Epson (or other brand) driver and RIPs (I use imageprint).

Alain
« Last Edit: April 04, 2006, 06:54:03 PM by alainbriot » Logged

Alain Briot
Author of Mastering Landscape Photography, Mastering Composition, Creativity and Personal Style., Marketing Fine Art Photography and How Photographs are Sold.
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digitaldog
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« Reply #4 on: April 05, 2006, 09:01:44 AM »
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I don't agree with their recommendation at all! IF there's an issue with black mapping in the profile, BPC will help a great deal. IF the profile has no issue, it does nothing. There's a PDF on my site that explains what BPC does. Unless you have a really screwed up profile, you always want it on. IOW, it either helps or does nothing.
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Andrew Rodney
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paulbk
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« Reply #5 on: April 05, 2006, 04:41:10 PM »
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It’s no wonder mere mortals like me are confused. Alain Briot makes stunning world class prints and Andrew Rodney is a world class digital color guru, and yet they don’t see BPC the same way. Oye vey!

You’d think the move to digital would make post processing and printing more scientific and therefore deterministic. Nope.
« Last Edit: April 05, 2006, 04:45:37 PM by paulbk » Logged

paul b. kramarchyk
Barkhamsted, Connecticut, USA
Stephen Best
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« Reply #6 on: April 05, 2006, 06:05:41 PM »
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I don't agree with their recommendation at all! IF there's an issue with black mapping in the profile, BPC will help a great deal. IF the profile has no issue, it does nothing. There's a PDF on my site that explains what BPC does. Unless you have a really screwed up profile, you always want it on. IOW, it either helps or does nothing.
[{POST_SNAPBACK}][/a]
I struggled with the same thing and decided that, on the range of rag papers I use with the Epson driver, I got better results with it "Off" (Perceptual only). I note that BPC "Off" is also the recommendation of a number of paper manufacturers (Hahnemühle, Crane ... links below). I don't think they propose this simply to inflate apparent Dmax. Maybe if your shadows were clipped, BPC "On" may be more useful. With Rel/Col however and the Epson driver, BPC "Off" is a disaster.

I'd be interested to know your reasoning why you think BPC could be beneficial with Perceptual. The results I've seen don't seem to bear this out.

[a href=\"http://www.hahnemuehle.com/site/en/470/epson.html]http://www.hahnemuehle.com/site/en/470/epson.html[/url]
http://www.crane.com/museo/profiles.aspx
« Last Edit: April 05, 2006, 06:06:41 PM by Stephen Best » Logged
digitaldog
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« Reply #7 on: April 05, 2006, 06:18:32 PM »
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I'd be interested to know your reasoning why you think BPC could be beneficial with Perceptual. The results I've seen don't seem to bear this out.

The rendering intent should be immaterial. Now I don't know who's profiles you're using or how they are handling a Perceptual intent. There is absolutely no standard in how a manufacturer builds a perceptual rendering. To Quote myself:

Because there is no standard specification for how ICC profiles map solid black from the source color space to the destination color space, there are cases where the solid black of an image can produce less than solid black in the resulting converted image.
To correct these possible problems,Adobe has a switch in the ACE CMM called Black Point
Compensation. Turning this switch on causes ACE to ignore the actual luminance of black in
the source color space.With this switch on,the darkest black in the source space is mapped to
the darkest black in the destination.

So, is there a compelling reason you don't want to map Black this way? I've seen some wacky RGB profiles that produce poor results with BPC but I haven't run into one in years. As I said, if there's an issue with the black mapping, BPC helps. If there isn't, it does nothing. If you uncheck it, you'll either see no change, or you'll see why you generally want it turned on.
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Andrew Rodney
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« Reply #8 on: April 05, 2006, 06:25:53 PM »
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One company is using Fuji's ColorKit to build the profiles. I have a copy but dont' use it (it's OK but not anywhere near the top of my list).

The other is using ProfileMaker Pro. I imported the profile so I can see the settings they are using. I can't fathom why they are using the settings they are (Logo Classic, Neutral Paper, small profile size). They may have a reason and I don't think this has anything to do with BPC but these are settings I personally wouldn't nor do not use when I build profiles.
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Andrew Rodney
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Stephen Best
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« Reply #9 on: April 05, 2006, 06:43:27 PM »
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So, is there a compelling reason you don't want to map Black this way?
I agree, it sounds like the logical thing ... but practice is different. I found on rag BPC "On" either did nothing or pushed the shadows way too high. The same with both custom and downloaded profiles. Some other manufacturer (which currently eludes me) stated that BPC "On" or "Off" was a judgment call and they wouldn't want to make a recommendation either way. It all sounds like voodoo to me. Anyway, I'll stick with what gives me the best results for now until I can afford to move to a RIP and build my own CMYK profiles.
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Stephen Best
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« Reply #10 on: April 05, 2006, 11:49:18 PM »
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There's a PDF on my site that explains what BPC does. Unless you have a really screwed up profile, you always want it on.
Obviously not this one:

http://www.digitaldog.net/files/Black_Point_Compensation.pdf

:-)
« Last Edit: April 05, 2006, 11:49:47 PM by Stephen Best » Logged
Brian Gilkes
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« Reply #11 on: April 07, 2006, 05:26:34 PM »
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The plot and perhaps the air thickens.
I received my first roll of Silver Rag yesterday. Last night I downloaded the Crane canned profile (perceptual and BPC off). I'm about to print test charts per Crane recommendation and with my standard settings , print both on the 9800, and send to Les Walkling to read and build custom profiles.
We'll see what comes up. I would strongly suspect that with a colour space big enough to encompass the K3 ink gamut the answer is a custom profile using Rel Col and BPC on.
Cheers
Brian.
www.pharoseditions.com.au
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K P
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« Reply #12 on: April 07, 2006, 08:45:57 PM »
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Hey Brian,

I'm waiting for my roll of Silver Rag to come in as well.  Its coming by accident actually cause I first ordered it, but then cancelled it after reading about the Fine Art Pearl paper, but I guess its on its way nevertheless.  Anyway, I'm reading about how glossy it is, and I wonder if you can give me your personal description.  I now have an Epson 4800 cause my 4000 had to be replared by Epson, and I'm missing my matte paper.  I really hoped that these new papers would be a substitute for matte in that you can print on it with the PK ink, but that they had a matte (non shinny) surface.

So I realize its kind of like a pearl now, but can you elborate any?  I have experience with Epson's Premium Luster and Semi-matte.  What I'd want is something close to enhanced matte, or ultra smooth fine art paper, but I think I'm dreaming.  So should I even open the box up.. will I be dissapointed?  I just don't like the reflections from these papers under glass.

Kiran
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TomTom60
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« Reply #13 on: April 08, 2006, 01:09:27 AM »
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Kiran,

Are you wondering whether Crane Silver rag is "like a pearl"?? is that correct?

Silver rag is nothing like a pearl surface. It is a glossy, bumpy surface on a warm, heavy base sheet. Think semi-matte only with bigger bumps. If it is not illuminated correctly it will pick up highlights in the bumps...stipples, whatever you want to call them. It has a defined texture that seems to become more apparent when you lay ink onto it. You can make beautiful prints with it and as long as they are lit properly (from above with the light source about 30 or so degrees from the wall) they will look grand. I dont like the texture. Im much more interested in the offerings from Innova/Da Vinci and perhaps the Hannemuhley "Pearl" surface...not sure what this describes yet...I have to see it i think.

These papers are not a substitute for matte papers where you can print with the blacker PK ink. they are the beginnings of an answer for a real, bw, fine art printing stock.

 In some sense..matte papers were a replacement for these papers because these papers didnt exist before. These papers are designed to fill a gap that has existed since high quality digital printing was available. The need for a paper that really looked as good as a traditional black and white print.

Matte papers became the go to paper because they looked better than the rc papers AND because they didnt show itches like gloss differential or bronzing. the trade off here is the lack of real black in the MK ink. K3 inks have almost eliminated..almost...these problems so now these "traditional gloss" papers are coming out in droves. Thanks be to those who finally have put effort towards designing a paper that looks close to a real black and white print.
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Hermie
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« Reply #14 on: April 08, 2006, 03:41:59 PM »
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This one explains what BPC does:
[a href=\"http://www.color.org/Adobe1bpc.pdf]http://www.color.org/Adobe1bpc.pdf[/url]

Herman
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Stephen Best
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« Reply #15 on: April 08, 2006, 05:37:29 PM »
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This one explains what BPC does:
http://www.color.org/Adobe1bpc.pdf

Herman
[a href=\"index.php?act=findpost&pid=62172\"][{POST_SNAPBACK}][/a]
Thanks for the detailed description. Obviously this isn't a precise science, it depends on the shape of the space etc., which explains why the results are variable.

I was only pointing out to Andrew that his recommendations today contradict those from his earlier paper, written then for PS5.
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Mark D Segal
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« Reply #16 on: April 09, 2006, 10:04:01 AM »
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Fraser, Murphy and Bunting as well as Fraser & Blatner (Real World Color Management and Real World Photoshop CS2 respectively) are unequivocal that BPC should be enabled at all times, unless one is experimenting to see what difference it makes. Fraser and Blatner have a particularly lucid explanation for this recommendation in their inset on page 210 titled "Black is Black (or Is It?). Nothing in any of these explanations suggests that the decision whether or not to use BPC depends on the paper. Of course newer inkjet printing papers have appeared on the market since these books were published, but the principles described therein don't indicate a logic that would be influenced by the characteristics of the paper - at least none that is not obvious to me.
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Mark D Segal (formerly MarkDS)
Author: "Scanning Workflows with SilverFast 8....." http://www.luminous-landscape.com/reviews/film/scanning_workflows_with_silverfast_8.shtml
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« Reply #17 on: April 09, 2006, 01:40:56 PM »
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I have all my papers and inksets custom profiled and I see little if any difference on the BPC state. However initially using stock profiles, well I could yeah there are cases for using and not using it.
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bruce fraser
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« Reply #18 on: April 16, 2006, 09:29:01 PM »
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Black Point Compensation in Photoshop 5.x was unsafe for RGB-to-RGB conversions and often produced hideous results, which is probably why Andrew recommended leaving it turned off for inkjet printing from Photoshop 5.x.

It got fixed in Photoshop 6. Now it either does nothing, or it makes sure that black in the source is mapped to black in the image. I've yet to find a situation where this wasn't desirable behavior, though it has sometimes led me to edit the image to close the shadows down a little.

Compressing shadows is pretty much always a safe operation. But if the shadow detail has been clipped, which often happens with BPC turned off, there's nothing you can do to open them up again.

While its effect is usually more subtle with Perceptual rendering than with relcol, it's equally necessary with some pairs of source and destination profile in perceptual and in relcol. If an image looks significantly better with BPC turned off, the first thing I'd do is to check all the profiles involved....
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Stephen Best
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« Reply #19 on: April 16, 2006, 11:33:30 PM »
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While its effect is usually more subtle with Perceptual rendering than with relcol ...

Why is there a difference at all between the two? This to me implies that perceptual munges the black point along with the gamut and what you're getting with BPC is (sometimes) a double adjustment ... whereas relcol by itself has no means to adjust the black point and is reliant on outside help (BPC) to address it.

Why, if I soft-proof an image with a profile for rag (with an obvious difference in the blacks and a value set for the black point tristimulus) don't I see a change on-screen when I toggle BPC with perceptual rendering?

Lastly why, since there's an obvious requirement, hasn't this been incorporated into the ICC specs?

Questions, questions ... :-)
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