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Author Topic: Red River Palo Duro Etching matte paper on Epson 3880 - first look  (Read 2847 times)

Mark D Segal

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Re: Red River Palo Duro Etching matte paper on Epson 3880 - first look
« Reply #20 on: June 05, 2017, 09:08:28 PM »

Pat has raised a very intriguing prospect about the use of a polarizer filter. With hindsight, it's kind of surprising we hadn't heard more about that in the past from X-Rite or from our other usual sources of Color Management expertise. The first question I would have is whether reading matte profiling targets with such a filter buys one a profile that would actually cause an ink laydown that returns a minimum value of L*5 (Maximum Black) or so on a matte paper.
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Mark D Segal (formerly MarkDS)
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MHMG

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Re: Red River Palo Duro Etching matte paper on Epson 3880 - first look
« Reply #21 on: June 05, 2017, 09:32:41 PM »

Pat has raised a very intriguing prospect about the use of a polarizer filter. With hindsight, it's kind of surprising we hadn't heard more about that in the past from X-Rite or from our other usual sources of Color Management expertise. The first question I would have is whether reading matte profiling targets with such a filter buys one a profile that would actually cause an ink laydown that returns a minimum value of L*5 (Maximum Black) or so on a matte paper.

It would indeed return the minimum value measured if you use the same spectro/filter combination to measure the printed output. The questions more to the point are: 1) What do observers perceive, something closer to the darker measured value or to the lighter measured values for deep shadows and maximum printed blacks in the printed image? Neither one is likely to perfectly match human perception in a real world viewing environment, but which one is on average the closer choice? 2). Which profile, i.e., the one with the polarized and thus darker measured shadow values or the non polarized one with the lighter measured values is likely to assist the user in producing optimal printed output?  The one with darker measured shadow values will indeed give a softproofed image with better visual contrast, but that in turn would suggest less demanding edits are then called for to open up shadow details while in softproof mode, but that in turn might lead to a print with even less shadow separation for any printmaker who goes to the trouble of editing images carefully when using the non polarized version of an ICC profile for matte media. Again, it all depends on what the viewer actually sees when looking at the printed output. I don't know the answer. Perhaps Patrick and Steve at Chromix.com have done those studies and concluded polarized instruments make for better profiles. Any profile returning lower L*min values in softproof mode will exhibit more visual contrast in softproof mode, but does that make for better printed output?  I haven't done those studies, so I honestly don't know the answer.

best,
Mark
http://www.aardenburg-imaging.com
« Last Edit: June 05, 2017, 10:18:35 PM by MHMG »
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Alan Goldhammer

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Re: Red River Palo Duro Etching matte paper on Epson 3880 - first look
« Reply #22 on: June 05, 2017, 09:42:47 PM »

Good point on the difference between the observer and a spectrometer.  I think one has to do some printing to see if there is a real difference.  Theoretically, if the B/W range is extended with a deeper black point it should lead to more separation.
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Mark D Segal

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Re: Red River Palo Duro Etching matte paper on Epson 3880 - first look
« Reply #23 on: June 05, 2017, 09:54:09 PM »

Good point on the difference between the observer and a spectrometer.  I think one has to do some printing to see if there is a real difference.  Theoretically, if the B/W range is extended with a deeper black point it should lead to more separation.

Sure, and a difference between L*5 and L*15 would be definitely visible.

But I would still like to see a demonstration somehow of the round-trip minimum L* value between a profiling target read with polarizer-equipped spectro and the black patch value of a print using that profile. Mark's observation that it should work sounds plausible of course, but this is so novel I'm in "show me" mode.
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Mark D Segal (formerly MarkDS)
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Alan Goldhammer

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Re: Red River Palo Duro Etching matte paper on Epson 3880 - first look
« Reply #24 on: June 05, 2017, 10:23:40 PM »

Something still seems strange to me.  I pulled out my old optics text to see if there might be an explanation but that just showed how much math I have forgotten. 

If you think about it the printer prints a maximum black based on the driver and paper settings.  This is fixed but we make two measurements using different instruments.  What does this mean?  I need to sleep on this.
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MHMG

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Re: Red River Palo Duro Etching matte paper on Epson 3880 - first look
« Reply #25 on: June 05, 2017, 10:58:42 PM »

Something still seems strange to me.  I pulled out my old optics text to see if there might be an explanation but that just showed how much math I have forgotten. 

If you think about it the printer prints a maximum black based on the driver and paper settings.  This is fixed but we make two measurements using different instruments.  What does this mean?  I need to sleep on this.

Me, too. But one thing for sure. The black patch I just measured with two distinctly different values in polarized versus non polarized instrument mode didn't change its appearance in terms of how I perceive it under any given lighting condition. It only got a lower value assigned to it with polarized data set versus the non polarized data set. Whether that makes for better, worse, or no difference in the ICC profile values sent to the printer is unclear.  As for softproofing, I have no doubt the polarized data set will create an inverse transform LUT in the profile that will appear to have more visual contrast and color saturation in the softproof on screen. You can just turn a matte media softproof mode off if you want to see how increased image contrast appears on screen.  Yet, the question remains "how does it print?".

best,
Mark
http://www.aardenburg-imaging.com
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Stephen Ray

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Re: Red River Palo Duro Etching matte paper on Epson 3880 - first look
« Reply #26 on: June 05, 2017, 11:04:06 PM »

Who Knew!

If you can get your hands on a “Batamag 12X wide field magnifier with dual LED lights”, the experience could be a real eye-opener. I suspect the view, with all its problems, is very similar to what the common spectrophotometer sees. Lots of glare from texture on certain media.

Link to the Betamag loupe source

So, “Who Knew?”

Some folks who design fine art gallery lighting and who use polarized light sources for copy work or regularly check printing tests and rosettes using a common loupe in the industry might have an idea.

As an illustration to portray what an unpolarized light source reflects as a worst-case…
Attached is a photo of the right side of the Bill’s Balls test image printed on a popular, premium glossy canvas from an Epson GS6000. (The metal object along the right edge is the back side of a 13 inch Kodak mercury thermometer acting as a weight to hold the print flat.) Although the common spectrophotometers only measure a very small swatch, the sightline is as troublesome. In this particular case of profiling, the typical readings produced hard-edged banding in some of the gradients and was solved by using the profile from the Satin finish canvas instead. Unfortunately, the alternative to use a polarized spectro was not in the cards at the time.

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Stephen Ray

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Re: Red River Palo Duro Etching matte paper on Epson 3880 - first look
« Reply #27 on: June 05, 2017, 11:39:58 PM »

Yet, the question remains "how does it print?".

Quoting a snip from the Chromix blog from April 30, 2010 about the Barbieri Spectro LFP Series 3 with polarizing filter: 
<if you make printer profiles for media that has flat or bumpy surfaces like canvas or other fabrics - this will get you the shadow detail in your profiles that you won't get any other way.>

This makes sense to me because shadow detail is a common problem with canvas and, with a loupe, you can see white specular highlights against the black(ish) field. Therefore, it seems the profile software could interpret darks as too light and erroneously make them darker.


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Ernst Dinkla

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Re: Red River Palo Duro Etching matte paper on Epson 3880 - first look
« Reply #28 on: June 06, 2017, 03:31:10 AM »

Reading the specs of modern spectrometers, polarized measurements right now are M3 measurements that do not include UV light. That may not be a real problem as I guess a lot of profiles used by forum members are made with UV cut spectrometers anyway. OBA effect added to the measurements are then often extrapolated from readings in the visible spectrum. I wonder whether the SpectraScan could use both UV + polarized filtering in one measurement. Another question is whether measurements with a polarization filter have an influence on the rest of the tone range including paper whites, it must be a diminishing effect.

Edit2:
Given the above, it should be good to measure in both conditions OBA free and OBA containing papers and see what happens then with Dmax L numbers.

Matte and gloss texturised papers and canvasses both exist and anything in between including horrible glossy embossed textures, I would expect the glossy ones to be even more prone to deviations like mentioned. A perfect Ulbricht integrating sphere should cope with this, the 45 degr light cone of most spectrometers in use does not cope it seems.


Edit1:
Bringing this to the color management forum with the right subject line may give us better information from people like Graeme Gill, no offense meant to the forum members here.

Met vriendelijke groet, Ernst

http://www.pigment-print.com/spectralplots/spectrumviz_1.htm
March 2017 update, 750+ inkjet media white spectral plots

« Last Edit: June 06, 2017, 12:12:39 PM by Ernst Dinkla »
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Ernst Dinkla

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Re: Red River Palo Duro Etching matte paper on Epson 3880 - first look
« Reply #29 on: June 06, 2017, 03:56:50 AM »

Me, too. But one thing for sure. The black patch I just measured with two distinctly different values in polarized versus non polarized instrument mode didn't change its appearance in terms of how I perceive it under any given lighting condition. It only got a lower value assigned to it with polarized data set versus the non polarized data set. Whether that makes for better, worse, or no difference in the ICC profile values sent to the printer is unclear.  As for softproofing, I have no doubt the polarized data set will create an inverse transform LUT in the profile that will appear to have more visual contrast and color saturation in the softproof on screen. You can just turn a matte media softproof mode off if you want to see how increased image contrast appears on screen.  Yet, the question remains "how does it print?".

best,
Mark
http://www.aardenburg-imaging.com

I recall experiences where matte prints black areas looked different in density but did not differ in L value or showed reversed L numbers. My friend Bernard and me and early Canon iPF printer versus Epson models on Hahnemühle texturised papers. Not at all scientifically theorized or researched afterwards. Just uttered: instruments and humans.

Met vriendelijke groet, Ernst

http://www.pigment-print.com/spectralplots/spectrumviz_1.htm
March 2017 update, 750+ inkjet media white spectral plots

« Last Edit: June 06, 2017, 10:21:14 AM by Ernst Dinkla »
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Mark D Segal

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Re: Red River Palo Duro Etching matte paper on Epson 3880 - first look
« Reply #30 on: June 06, 2017, 08:32:32 AM »

I recall experiences where matte prints black areas looked different in density but did not differ in L value or showed reversed L numbers. ............

Agree. I've reported on such experiences in my review of the Canon Pro-2000 printer and some papers that Canon had brought to market - cases where differences of apparent Black density are larger than differences of L* values would suggest they may be.
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Mark D Segal (formerly MarkDS)
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MHMG

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Re: Red River Palo Duro Etching matte paper on Epson 3880 - first look
« Reply #31 on: June 06, 2017, 11:38:46 AM »

Reading the specs of modern spectrometers, polarized measurements right now are M3 measurements that do not include UV light. That may not be a real problem as I guess a lot of profiles used by forum members are made with UV cut spectrometers anyway. OBA effect added to the measurements are then often extrapolated from readings in the visible spectrum. I wonder whether the SpectraScan could use both UV + polarized filtering in one measurement. Another question is whether measurements with a polarization filter have an influence on the rest of the tone range including paper whites, it must be a diminishing effect.

Edit: bringing this to the color management forum with the right subject line may give us better information from people like Graeme Gill, no offense meant to the forum members here.

Met vriendelijke groet, Ernst

http://www.pigment-print.com/spectralplots/spectrumviz_1.htm
March 2017 update, 750+ inkjet media white spectral plots

Hello Ernst,  thanks for supplying the M3 term for the polarized measurement mode. I had forgotten about it, and probably with good reason. BTW, the Gretag Spectrolino/Spectroscan models measure M0, M2, and M3. M1(with more specified UV in the instrument's light source) is the missing one because it was defined only recently. Only one filter condition can be used at a time so, M3 +M2 combined can't be measured, but fortunately I don't think it's all that necessary for the reasons you also stated, and then some. 

After some further M0 and M3 measurements on various media (including a Macbeth Color checker chart which has matte finish patches and a Kodak greyscale that has glossy photographic "F" surface finish, I don't think M3 is all that useful a mode for making ICC profiles with most photographic and fine art inkjet media. It will indeed open up shadows but at a significant mismatched expense to softproofing and to midtone lightness and chroma reproduction. I base this opinion on the fact that as RGB values go down and the printed ink density rises,  the M3 condition measures progressively darker and more saturated LAB values compared to M0 (or M1). The CMM's evaluation of the forward transform of the profile will then be attempting to both lighten the whole printed density scale and desaturate as well. This could be an interesting "rendering" condition for some images on some matte media, but I think the color errors are just too high to expect that further image edits won't be necessary to make a good print, and furthermore, those edits will have to be done without benefit of accurate softproofing. The softproof will appear richer and more contrasty while the actual print will appear lighter, with possibly more separation in the shadows at the expense of midtones plus lower in overall color saturation. Here's a few measured L* values:

For Macbeth ColorChecker black patch:  M0 L*= 20. 6, M3 L*=6.7 (note: the published value for this black patch agrees with MO measurement)
For Macbeth ColorChecker midtone grey patch M0 L* =50.7, M3 = 44.1 (note: the published value for this black patch agrees with MO measurement)
For the  Macbeth ColorChecker green patch   M0 Lab = 54.2, -39.4, 34.1  whereas   M3 Lab = 50.1,-47.5, 41.7 (i.e. darker and more saturated), so to print a match to the digitally encoded green patch value using a digital version of the chart, a profile made with M3 condition will attempt to send a higher and less vivid RGB triplet to the printer compared to a profile made with M0, M1, or M2 conditions. That can't be good with respect to the final printed color accuracy.

I looked at some Moab Entrada color patches as well with M0 and M3 measurements. Similar story. Also interesting was comparing the Entrada max printed black value made with my Z3200 to the Entrada max printed value made with my Epson P600. The M0 measurement was 17.0 for the Z3200 on this paper and the P600 measured 17.7.  For M3 measurement, HP dropped to 5.6 and P600 value dropped to 1.0!!!!  Now we have a good reason to believe why RR's profiles are showing such low L*min values. The were likely built with M3 measurements. However, to my eye, both the Z3200 print and the P600 print both had very consistent visual appearance in the black printed patches, and to my eye a good black but definitely not worthy of L=1.0 when looking at them in various lighting conditions in my studio. M0 measurements are thus closer to what I think makes visual sense to the human observer when viewing most photographic and/or fine art media, and logically, it now makes total sense to me why M3 is rarely used to make ICC profiles of photographic and inkjet media.

That said, I will go ahead today and build two profiles for the Entrada Rag Natural paper (no OBAs), one using M3 data and the other using the conventional M0 data. It will be very interesting to see if the M3 built profile prints the way I anticipate it will, and whether the rendered outcome has any useful relevance in the profile maker's toolbox  :)

cheers,
Mark
http://www.aardenburg-imaging.com
« Last Edit: June 06, 2017, 11:46:51 AM by MHMG »
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Ernst Dinkla

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Re: Red River Palo Duro Etching matte paper on Epson 3880 - first look
« Reply #32 on: June 06, 2017, 12:19:57 PM »

Hello Ernst,  thanks for supplying the M3 term for the polarized measurement mode. I had forgotten about it, and probably with good reason. BTW, the Gretag Spectrolino/Spectroscan models measure M0, M2, and M3. M1(with more specified UV in the instrument's light source) is the missing one because it was defined only recently. Only one filter condition can be used at a time so, M3 +M2 combined can't be measured, but fortunately I don't think it's all that necessary for the reasons you also stated, and then some. 

After some further M0 and M3 measurements on various media (including a Macbeth Color checker chart which has matte finish patches and a Kodak greyscale that has glossy photographic "F" surface finish, I don't think M3 is all that useful a mode for making ICC profiles with most photographic and fine art inkjet media. It will indeed open up shadows but at a significant mismatched expense to softproofing and to midtone lightness and chroma reproduction. I base this opinion on the fact that as RGB values go down and the printed ink density rises,  the M3 condition measures progressively darker and more saturated LAB values compared to M0 (or M1). The CMM's evaluation of the forward transform of the profile will then be attempting to both lighten the whole printed density scale and desaturate as well. This could be an interesting "rendering" condition for some images on some matte media, but I think the color errors are just too high to expect that further image edits won't be necessary to make a good print, and furthermore, those edits will have to be done without benefit of accurate softproofing. The softproof will appear richer and more contrasty while the actual print will appear lighter, with possibly more separation in the shadows at the expense of midtones plus lower in overall color saturation. Here's a few measured L* values:

For Macbeth ColorChecker black patch:  M0 L*= 20. 6, M3 L*=6.7 (note: the published value for this black patch agrees with MO measurement)
For Macbeth ColorChecker midtone grey patch M0 L* =50.7, M3 = 44.1 (note: the published value for this black patch agrees with MO measurement)
For the  Macbeth ColorChecker green patch   M0 Lab = 54.2, -39.4, 34.1  whereas   M3 Lab = 50.1,-47.5, 41.7 (i.e. darker and more saturated), so to print a match to the digitally encoded green patch value using a digital version of the chart, a profile made with M3 condition will attempt to send a higher and less vivid RGB triplet to the printer compared to a profile made with M0, M1, or M2 conditions. That can't be good with respect to the final printed color accuracy.

I looked at some Moab Entrada color patches as well with M0 and M3 measurements. Similar story. Also interesting was comparing the Entrada max printed black value made with my Z3200 to the Entrada max printed value made with my Epson P600. The M0 measurement was 17.0 for the Z3200 on this paper and the P600 measured 17.7.  For M3 measurement, HP dropped to 5.6 and P600 value dropped to 1.0!!!!  Now we have a good reason to believe why RR's profiles are showing such low L*min values. The were likely built with M3 measurements. However, to my eye, both the Z3200 print and the P600 print both had very consistent visual appearance in the black printed patches, and to my eye a good black but definitely not worthy of L=1.0 when looking at them in various lighting conditions in my studio. M0 measurements are thus closer to what I think makes visual sense to the human observer when viewing most photographic and/or fine art media, and logically, it now makes total sense to me why M3 is rarely used to make ICC profiles of photographic and inkjet media.

That said, I will go ahead today and build two profiles for the Entrada Rag Natural paper (no OBAs), one using M3 data and the other using the conventional M0 data. It will be very interesting to see if the M3 built profile prints the way I anticipate it will, and whether the rendered outcome has any useful relevance in the profile maker's toolbox  :)

cheers,
Mark
http://www.aardenburg-imaging.com

I added some edits to my message. A spectrometer with a better integrating sphere would be the right answer to the problem in my opinion. that is beyond handheld ones.


Met vriendelijke groet, Ernst

http://www.pigment-print.com/spectralplots/spectrumviz_1.htm
March 2017 update, 750+ inkjet media white spectral plots
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GrahamBy

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Re: Red River Palo Duro Etching matte paper on Epson 3880 - first look
« Reply #33 on: June 06, 2017, 12:44:13 PM »

Something still seems strange to me.  I pulled out my old optics text to see if there might be an explanation but that just showed how much math I have forgotten.

Possibly what is happening is that matte paper is scattering the polarisation: if you light it with light that is strongly polarised in a given orientation (ie E-field vertical) and it is reflected after being scattered into random angle, in addition to a proportion absorbed by the pigment. A viewer with no polarisation preference would see the full amount of light reflected, whereas one viewing through a narrow angle polariser would see only the vertical component: ie the average over theta of cos²(theta), which would reduce the measured return by a factor of 1/2.

It would be interesting to measure the light reflected in each of the two orientations, ie with the receiver polariser parallel or orthogonal to the illumination polariser...
 
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MHMG

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I built two profiles today, one with M0 measurements and one with M3 measurements of a TC918 color target printed by my Epson P600 on Moab Entrada Natural. I used BasicColor Drop RGB as the profiling software.  Because Entrada Natural is OBA-free, my M0 measurements will match M1 and M2 conditions as well. M3 is the odd one out, measuring the colors significantly darker and more saturated as I discussed earlier in this thread. The result was as I predicted. M3 data does indeed open up deep shadows, but it comes at a price in overall color and tone fidelity at least when using matte finish media.

The M0 data set made a profile which delivered a predictable and color accurate print of the Macbeth ColorChecker chart and also this Aardenburg test target (attached) which exercises the full sRGB color and tonal gamut in 12 Lab hue planes plus skintone quadrants. Softproof in PS with "simulate paper color" turned on was colorimetrically accurate on screen and a good match to the printed output. The prints made with the profile using the M3 data set did indeed exhibit very open shadows, but it came at the expense of midtone lightness and contrast relationships as well as reduced color saturation in the finished print. So pick your poison as to what image edits you want to make to improve your color reproduction on matte media. The M3 data set makes it more challenging not less, IMHO. Also Softproofing is no longer accurate, definitely not with "simulate paper color" invoked when using the M3 data set. Some folks call the simulate-color-paper feature the "make it look ugly button" and don't use this softproof feature, but I use it all the time, because it forces one to make very specific edits to restore visual contrast to the image reproduction on matte papers.  Thus, the M0,M1,or M2 data sets are required to simulate the printed colors accurately. Profiles made with M3 data give up that feature, and even if you don't invoke it in PS but still turn on softproofing, the softproof is still not quite right. Hence, M3 built profiles will require more iterative printing to achieve edits to correct color saturation, midtone lightness and contrast, etc. I don't think that is a very good tradeoff for the sake of opening up shadows for which there are many other useful tools to achieve the same desired effect in PS, LR, and other image editing apps.

Interestingly enough the printed output from the M3 profile wasn't so far off the beam that many people would reject the profile out of hand. For amateur printmakers like many of Red River's customers, they might be perfectly satisfied with this profile output quality. However, it's definitely not a profiling methodology I would recommend to discerning printmakers for photographic and fine art media. Perhaps the exception is seriously glossy and textured canvas media that show lots of specular highlights off the surface and where the polarizing filter will help to reduce those color robbing reflections. I never print on that type of canvas, so I can't say for certain.

cheers,
Mark
http://www.aardenburg-imaging.com
« Last Edit: June 06, 2017, 03:22:20 PM by MHMG »
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Alan Goldhammer

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Interestingly enough the printed output from the M3 profile wasn't so far off the beam that many people would reject the profile out of hand. For amateur printmakers like many of Red River's customers, they might be perfectly satisfied with this profile output quality. However, it's definitely not a profiling methodology I would recommend to discerning printmakers for photographic and fine art media. Perhaps the exception is seriously glossy and textured canvas media that show lots of specular highlights off the surface and where the polarizing filter will help to reduce those color robbing reflections. I never print on that type of canvas, so I can't say for certain.

cheers,
Mark
http://www.aardenburg-imaging.com
Is the target you posted the "Hue Slice" image from the website?  If so, can I print it directly from LR after converting it in Photoshop?

I understand the point about really glossy papers and how a polarizing filter might help out in that case.  I'm still baffled by the effect seen with matte papers where one doesn't get as much reflection.  One would be concerned if there was color shifting taking place using the RR profile approach.  I'll see when I do some test prints.

Unblocking highlights is easy to understand as the black point gets shifted to that the range from paper white to pure black is extended with a spectro read of L* = 5 compared to L* = 18 (the normal case I observe when profiling matte papers using Argyll).  The darker shadow tones would see more separation BUT is this only something that is seen under soft proofing?  As I noted in an earlier post, the true black on the print is not changing, only the apparent reading is.  It's all pretty strange and I'll wait to see what the prints end up looking like.
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MHMG

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Is the target you posted the "Hue Slice" image from the website?  If so, can I print it directly from LR after converting it in Photoshop?


The hue slice target  you are referring too is different. The one attached in this thread is not currently available on the Aardenburg website. I should probably put it there, but if you save out the one attached in this thread, it's a jpeg in sRGB colorspace, so it should import and print just fine in PS or LR onto a letter-size sheet of paper. The lab hues were designed and encoded originally working in LAB colorspace, but were intended to port in gamut to sRGB colorspace, so this jpeg version will serve the same useful color reproduction evaluation purpose as the master file from which it is derived.

kind regards,
Mark
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Alan Goldhammer

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The hue slice target  you are referring too is different. The one attached in this thread is not currently available on the Aardenburg website. I should probably put it there, but if you save out the one attached in this thread, it's a jpeg in sRGB colorspace, so it should import and print just fine in PS or LR onto a letter-size sheet of paper. The lab hues were designed and encoded originally working in LAB colorspace, but were intended to port in gamut to sRGB colorspace, so this jpeg version will serve the same useful color reproduction evaluation purpose as the master file from which it is derived.

kind regards,
Mark
Thanks, I've downloaded it. 

Alan
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stockjock

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Re: Red River Palo Duro Etching matte paper on Epson 3880 - first look
« Reply #38 on: June 06, 2017, 05:21:26 PM »

Only on LuLu would you get this extraordinarily technical discussion of the intricacies of profile a matte paper.  I love it!

On a more prosaic note, if any of you does develop a great profile of the Palo Duro Etching paper and you aren't restricted by copyright/software limitations I hope you will share it. 

And just today Red River has made sample packs of the Palo Duro Etching paper available.  5 sheets for $4.99 including shipping.  I don't normally use textured papers but I've ordered a sample pack to see if I like it.  Link is:  http://enews.redriverpaper.com/q/Gs77EJbP8cue0XLSVwq99be2wW38cPFHW0sZcOJcGF1bC5yaWNrZXJ0QGdtYWlsLmNvbcOIEyzZmIjGfKLNYZUAQPmtnehcl2g

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Steve Upton

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Re: Red River Palo Duro Etching matte paper on Epson 3880 - first look
« Reply #39 on: June 06, 2017, 06:22:28 PM »



Hi all,

It's fascinating how much discussion this has brought up. As Pat mentioned, we've been using the polarizing filter, selectively, at CHROMiX for at least 17-18 years.

A few responses to questions / comments in the thread so far

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I wonder whether the SpectraScan could use both UV + polarized filtering in one measurement
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Only one filter condition can be used at a time so, M3 +M2 combined can't be measured

First, both M3 standard and the Pol filter for the 'Lino include UV filtering. So, by definition, M3 is really M3(+M2)

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The first question I would have is whether reading matte profiling targets with such a filter buys one a profile that would actually cause an ink lay-down that returns a minimum value of L*5 (Maximum Black) or so on a matte paper
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Theoretically, if the B/W range is extended with a deeper black point it should lead to more separation

As postulated above, using a Pol filter does not make the printer print to a higher density. For the measurement numbers it decreases the L* value as well as increases saturation, especially in the darker colors.

The physics are fairly simple. "First surface reflection" is the key here. In the case of a glossy surface there's very little light scattering and typically a spectral highlight reflection that we avoid viewing directly. The more bumpy the surface (and it increases as inks dry into the media) the more scattering that occurs from this first boundary. This scattering occurs before any ink colorants have a chance to do their filtering and often before the color of the media itself has an influence. So it's white light and it dilutes our perception of the color.

Polarization works in a least two ways. Light is naturally polarized when it reflects off a surface. This is why polarized sunglasses effectively cut the glare from car windows and the surface of water. Additionally, if the light source is polarized prior to reflecting off the sample, then there's a greater chance of the cross-polarized filter cutting down the first surface reflection. Just like sunglasses allow seeing fish in a river, polarized readings allow discrimination of shadow detail in print.

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...I don't think M3 is all that useful a mode for making ICC profiles with most photographic...

There are a lot of mental calisthenics that can go into this. For us, as I expect for most of you, the proof is in the pudding. Over the years we've found that Pol measurements greatly improve some profiles while not improving others. Surprises like significant improvements in some toner profiles compell us to try it in many different situations.

The reality is that neither instrument is likely "correct". Unfiltered i1's may measure 23 L* while a Pol filtered 'Lino or Barbieri spectro LFP may measure down to 2-5 L*. The reality is somewhere in between.

Here's an interesting test: . .
  • Print a graduated gray ramp on glossy paper and on the uncoated paper in question
  • Measure both and Write the measured L* value beside each patch
  • Place them under controlled lighting (not just color but angle of illumination as well)
  • Visually determine the match between the darkest patch on the uncoated paper and visual equivalent patch on the glossy paper

The L* value of the matching glossy patch will be lower than the uncoated patch and what the instrument probably should have measured, if it weren't for all the surface scattering. You can numerically stretch the uncoated paper's measurements down to that lower value and it will likely produce a profile that's better at proofing it's expected output. We've just added a feature to our Curve4 software that does this very scaling. It helps create a match between an uncoated press sheet (measuring too light) and a proof on proofing paper (Curve4 is for G7 calibration of digital and conventional presses, not really appropriate for this crowd)

But will it produce a profile that actually renders output better? Probably not.

Why?

When measurements are used to generate a profile and it's used for rendering output, it's mostly about relative mapping. The lightest point will map to paper white (even if you're using the wrong profile) and the blackest point will likely map to the blackest print point (due to the behavior of the perceptual intent or black point compensation with rel col intent).

So, the effect of Pol measurements is felt in two separate ways:

1. As mentioned, the lower L* and saturation creates a profile with a larger gamut volume and this will create soft proofs with a higher dynamic range. They are probably eggagerated somewhat, though we have scaled measurements to correct for this in the past.

2. The greater dynamic range of the measurement allows for the detection and encoding of more color gradation. This often translates into a profile that can address such detail and create prints that have fewer problems with washed out shadows. We've built thousands of profiles over the years and I can attest to it working, and working well, in some printing situations.

The situations in which it makes the difference is something we've arrived at through experimentation.

As for the instruments? Gretag MacBeth's SpectroLino/SpectroScan and the Barieri Spectro LFP are the two automatic instruments that we've used over the years - and the 'Lino's long out of production. Some hand-helds like the eXact, KMS FD-7 and SpectroDens will take M3 measurements and can measure strips in a manner similar to an i1Pro or be mounted in the ColorScout table. None of these solutions are inexpensive. - the polarization filter alone for the LFP is around $800 (!)

As Pat mentioned, we hound manufacturers continuously to add M3 to their instruments like the i1Pro, iSis and FD-9 but they haven't so far. M3 can cut down the light significantly so it slows the measurement process down, but for us it's worth it. Our SpectroScan tables with the Pol filter can take an hour and a half to measure a single target - which is why we have a bank of them. But again, when it's worth it, it's worth it.

I hope this helps.

Steve

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