gamut, intent and digital negatives

Do I need to be worried about out of gamut colors for digital negatives? Will they be capricious along the curve or inconsistent from file to file? If ok to use them for blocking colors, is there a better rendering intent and profile to use when printing? I've been using a 9180 with PS managed colors and relative colorimetric, with the HP advanced glossy profile on pictorico OHP.

Colin, someone more technically inclined will probably have a more technical answer for this, but I'll give a practical answer: since (I assume) you're determining the blocking color based on color patches or arrays printed from your printer, it's irrelevant whether Photoshop says the color is out of gamut. It's the color that the printer printed that's providing the right blocking for your process; the color that's on the computer, if it's different, isn't of particular interest.

There's no reason the color should be inconsistent from file to file; the blocking color you've chosen will remain the same regardless of the image, as long as you make sure your print settings remain constant. Someone else would have to answer the question about whether blocking colors behave differently at different points of the curve; I think there are those here who have studied such things, but that's an issue entirely unrelated to the out of gamut question, as I see it.
kt

Thanks Katharine, that was what I was hoping to hear, seeing as all the smoothest blocking colors off my printer seem to be renditions of out of gamut colors. Thanks for the help.

Yeah, all "out of gamut" means is that whatever printer your profile is set up for won't print that color exactly. But if the color as rendered by the printer is a good blocking color, who cares? The color I use for digital negatives for gum is an "out of gamut" color too, and works great.

This is a great question, and it brings up issues that I hadn't considered. That's probably because, I've been using the Burkholder method, and he recommends turning off all color management.

But if one's using color management, then I could see where rendering intent could have an effect. I can also see where black point compensation could have an even greater effect.

As to rendering intent, it may become important, if one is using saturated color to help block UV light. My inclination would be to use perceptual, as both the colorimetric (relative and absolute) clip saturated colors. This could result in loss of detail. Whereas, any effect that perceptual might have on an alternative image could be compensated for by adjusting exposure and contrast. (Like on pt/pd.) I offer these comments without benefit of experimenation!

Rendering intent affects the more highly saturated color. If one's not using this for help on UV blocking, I don't see where rendering intent would have that much of an effect. Best to stay consistent with what's worked in the past, though.

However, I could see black point compensation as having a large effect in the highlights of a print. It's hard to noodle how this might have an effect, so I could see trying with and without and seeing what works best. Since the purpose of black point compensation is to preserve detail in the shadows (on the negative), look for the setting that best preserves separation in the highlights of a print. But, black point compensation can also restrict density on the negative, and this too might cause a loss of detail in the highlights. Again, it's hard to noodle; best to experiment.

And, all this would depend on what profile one's using. Again, be consistent.

Many thanks Neil, lots to experiment with. I've been printing color charts at of different settings but haven't been able to find a good mix of uv blocking and smooth gradation. I hadn't thought about turning off black point, and turning off color management entirely sounds positively scandalous! Cant wait to try it out. :-> Thanks again.

Well, my mother used to say "a little knowledge is a dangerous thing," and perhaps I've just demonstrated that. I've spent the last half hour poring over my Photoshop bible studying about rendering intent and so forth and learned some things I didn't know before.

In Adobe 1998, which I thought Michael said was a good working RGB for ChartThrob so that's what I've used ever since, turning the black point compensation off completely messed up the shadows of some images I had open in Photoshop (lightened them to midtones) and they weren't restored to their proper values til I turned it back on.

Also, I'm still not sure why clipping saturated colors would matter, if there are clipped colors that work as blocking colors. I'm so far back in Photoshop (my last version before CS2 was Photoshop 5 --I also buy a new car once every 20 years or so) that I still thought that if I didn't find and check the "clip out of gamut colors" box it wouldn't clip them. But I see of course that now the clipping is done automatically. But only if you couldn't get a clipped color that was saturated enough to serve as a blocking color, would the clipping matter.... yes? no?

The bible also says that in CS2, the default intent is perceptual, but I found that mine was set to relative.

I'm beginning to think that Neil's got the best idea: just turn off color management entirely.

You're right, it was a very good question, but I'm not sure I like the extra complexity it introduces just when I was thinking I'd got things worked out to my satisfaction.

Katharine Thayer said:

Well, my mother used to say "a little knowledge is a dangerous thing," and perhaps I've just demonstrated that. I've spent the last half hour poring over my Photoshop bible studying about rendering intent and so forth and learned some things I didn't know before.

In Adobe 1998, which I thought Michael said was a good working RGB for ChartThrob so that's what I've used ever since, turning the black point compensation off completely messed up the shadows of some images I had open in Photoshop (lightened them to midtones) and they weren't restored to their proper values til I turned it back on.

Also, I'm still not sure why clipping saturated colors would matter, if there are clipped colors that work as blocking colors. I'm so far back in Photoshop (my last version before CS2 was Photoshop 5 --I also buy a new car once every 20 years or so) that I still thought that if I didn't find and check the "clip out of gamut colors" box it wouldn't clip them. But I see of course that now the clipping is done automatically. But only if you couldn't get a clipped color that was saturated enough to serve as a blocking color, would the clipping matter.... yes? no?

The bible also says that in CS2, the default intent is perceptual, but I found that mine was set to relative.

I'm beginning to think that Neil's got the best idea: just turn off color management entirely.

You're right, it was a very good question, but I'm not sure I like the extra complexity it introduces just when I was thinking I'd got things worked out to my satisfaction.

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Indeed! Starting to think digital negatives are like sausages, best not to ask too many questions about how they are made. When I first started I sort of rushed into a blocking color and chose a harsh one and set about plotting by hand wildly dramatic curves that needed a secondary curve just to deal with artifacts of the first one. Miraculously I got it just right, then I upgraded to from PS6 to CS3. Now I'm finding I cant replicate my results without getting venetian blinds so I'm pretty much starting from square one- except I cant seem to get beyond it- I'm struck dumb by all the possible permutations of profile, intent and color space, printer managed or ps managed, and oh so forth.

Mainly at this point I just want a profile and intent that will throw down some consistant and smooth blocking inks, but everything I'm trying looks like a pale washcoat until lots of black starts getting thrown into the mix, and they look overexposed when printing the arrays even at below my minimum to dmax times. Turning off the management sound very promising and I'm seriously considering blowing off tofu-turkey at the inlaws to run some more tests...as if I needed a reason.

It can be frustrating too the conflicting info out on the web and in print. I'd always heard that RGB1998 was the way to go as well, but then there those who say that sRGB is the space that all inkjet printers are calibrated to. Some say perceptual is best and others relative colorimetric. Everyone can agree that consistancy is the key, but I need to get to stable footing first. Thanks again for the help and thoughtful replies, and sorry if I passed along my headache.

edit- just printed Michael Koch-Schulte's HSL array from RGB 1998 with color management off and it is indeed printing with much more saturated colors; I do notice however a much more defined 'equatorial' line where densities sharply fall off. Although the line may well be too far into the shadows to have much impact on gradation. Looking forward to contact printing it. Thanks very much for this, I doubt it ever would have occurred to me to try it.

Colin Graham said:

I
edit- just printed Michael Koch-Schulte's HSL array from RGB 1998 with color management off and it is indeed printing with much more saturated colors; I do notice however a much more defined 'equatorial' line where densities sharply fall off. Although the line may well be too far into the shadows to have much impact on gradation. Looking forward to contact printing it. Thanks very much for this, I doubt it ever would have occurred to me to try it.

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You could make the printer work with many different settings but you must be consistent for repeatable results. I am attaching the first and second dialog boxes for the HP 9180 that I use. You may want to try them because I know for a fact that these work well for making digital negatives.

Sandy King

Colin Graham said:

It can be frustrating too the conflicting info out on the web and in print. I'd always heard that RGB1998 was the way to go as well, but then there those who say that sRGB is the space that all inkjet printers are calibrated to. Some say perceptual is best and others relative colorimetric. Everyone can agree that consistancy is the key, but I need to get to stable footing first. Thanks again for the help and thoughtful replies, and sorry if I passed along my headache.

edit- just printed Michael Koch-Schulte's HSL array from RGB 1998 with color management off and it is indeed printing with much more saturated colors; I do notice however a much more defined 'equatorial' line where densities sharply fall off. Although the line may well be too far into the shadows to have much impact on gradation. Looking forward to contact printing it. Thanks very much for this, I doubt it ever would have occurred to me to try it.

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There's a difference between the work space (that's defined by a profile) and the profile one selects for printing. My comments were directed more to the profile that's selected for printing.

Personally, I would never work in sRGB. For one thing, you might want to print some of the those alternative images in color. Printers can print colors which are out of gamut on many monitors. So, you'd lose those colors, if you worked in sRGB. sRGB is like working in a smaller room, when it comes to color gamut. The idea is to retain as much color as you can in the original image, and then accomodate as best one can when printing to a specific output medium. How you want to print will change in time, as new printers become available. In fact, for that reason, some prefer to work in Pro Photo color space, which is larger than Adobe '98.

Thanks for the reference Sandy. Nice to have something to compare directly to. I'm curious that you're using RGB 98 working space as the printer profile, is this better than using the HP advanced glossy profile that Pictorico recommends- or is that just intended to be used for the paper settings alone? The Pictorico website isnt very clear. Also, how do you print in color from a grey gamma document?

Thanks Neil, yes I thought I knew that there's a difference between the working space and the printer profile, I've been using the HP advance profile for printing on pictorico. But then again there are those that use the working space as a printer profile as Sandy's screen snaps suggest. I haven't tried this but it does bring up more questions. If Working RGB is different from the RBG working space I wish they'd call it something else! There are just so many possible combinations, but I'll get there. Thanks again for the help. All printer and paper sites seem to suggest that experimentation is the best first step, so that's what I'll continue to do.

(edit- I just want to clarify that I'm in no way deriding the performance of the 9180 printer, it's a wonderful printer, I'm absolutely impressed with the results I'm getting in B&W inkjet. And I know it's capable of wonderful digital negatives because I was getting them in PS6, just have to figure out how to get them again in CS3.)

I discovered two potential sources of my density problems- first, my printer kept resetting to defaults and trying to manage the color, so it was in conflict with the PS management. I need to remember to check that.

And second, I had somehow corrupted my copy of mkochsch's HSL array tiff- all the hues had slid to the left, so to speak, so the sampled values weren't corresponding to the coordinate values, if that makes sense. In other words, I was assigning blocking colors by hue and saturation coordinates instead of actually sampled values. Live and learn! Sorry to blog, but you never know, someone might find this useful...stranger things have happened..

I have wondered about the out-of-gamut issue for a few years now, and I think the short answer is: It's hard to say what will happen. I wonder if one of the issues I was initially having with my 7800 and the PDN approach was the fact that the driver was doing some goofy things with colors when the colorized densities for image gray values below 100% were shipped to the driver.

What happened is this. I picked a blocking color based on the straight-ahead PDN approach. This gave the RGB colors a maximum negative density. What would happen though, is when I used this color to colorize a negative ala PDN, the values below the maximum actually blocked more UV density than 100%! So, in other words, the 90% colorized patch blocked more UV than the 100% patch. Which doesn't make sense, unless the original RGB blocking color I picked was not actually a color the printer could create with the inks (out of gamut, IOW), and the non-linearity of the UV response was due to the less saturated version of the color gradually coming into gamut.

I think the analogy that the printer driver is like a big sausage grinder is apt. You know what goes in one end, and you can see what comes out the other, but I'm not really sure anyone outside the coding team at Epson understands what is going on in between.

I think it is a very interesting head-scratching exercise to get into photoshop and pull up the PDN pallet, Michael Koch-Schulte's arrays and my ternary diagram and then turn on the out-of-gamut warning display and soft-proof the pallet/array/triangle. You will find a lot of RGB combinations that just simply cannot be displayed on either your screen or the printer. What this means in terms of colorized negative creation is anybody's guess.

So, in my case, I ended up using the QTR approach, which worked very well, and life is good.

The gamut warning is indeed a sobering chunk of grayed-out info, and right in the heart of the best blocking colors at that, or it is on the B9180 anyway. But I didn't worry about it before I knew it was there so I'll try to revert a blind eye.

I had some non-linearity issues like you mention, though with composite black- the 98%-94% would get much lighter (print values) before going back in sequence. I tried lighter blacks like 12-12-12 and 18-18-18 (sampled from squares when the linearity resumed) but kept getting the same odd initial reversal in the densest parts of the step wedge. Driver inconsistencies make a whole lot of sense. Though in my case it was probably compounded by a hefty dose of user error...

I stayed up late and worked out several greens and an interesting rust color that look exceedingly smooth and actually curve with a bit of manners, so hopefully this means I've sorted out my color management issues. So I guess that means that with my OS (XP- god knows what hand Windows has in all of this) and my printer (9810) and my version of photoshop (CS3) I get the best results with Adobe RGB '98 colorspace/ application managed colors/ HP advanced glossy printer profile/ and perceptual rendering intent. And believe me I tried as many possible combinations as I could. Oh, and must recheck application managed colors in the printer dialogue box because that wants to reset to Colorsmart/RGB everytime a file is sent to the printer. I'm glad I braved facial ticks and an odd giggle to get a handle on this, I'm sure it'll make life much easier down the road.

Nice to have a record of this off the hard drives because surely that's the next thing that will go wrong! Cheers.

Colin Graham said:

Thanks for the reference Sandy. Nice to have something to compare directly to. I'm curious that you're using RGB 98 working space as the printer profile, is this better than using the HP advanced glossy profile that Pictorico recommends- or is that just intended to be used for the paper settings alone? The Pictorico website isnt very clear. Also, how do you print in color from a grey gamma document?

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Not sure I can give a good answer. I have just always used Adobe RGB 98 as my working space for color, and I let Photoshop manage color. I tried printer managed color but that did not give as much UV blocking as application managed. In making digital negatives we usually use the glossy paper setting in order to get as much detail as possible. However, as Clay observed, it does not appear to matter much, if any, if you use semi-matte or luster for the paper setting.

My only complaint about the HP 9180 is that loading Pictorico and other OHP materials is not as easy as with the Epson printers. In fact, I have had to send my printer back for a replacement because it quite sending the OHP through as it should.

But for regular printing in monochrome or color on matte type papers the results with the 9180 are outstanding.

Sandy

Oh yes, I've had a few episodes with the media tray, so far have been able to clear them by running the alignment routine, not sure what's going on there but it does seem overly fussy. Also, the 'automatically select' (main tray or media tray) option in the printer software never seemed to work either.