Luminous Landscape Forum
Raw & Post Processing, Printing => Printing: Printers, Papers and Inks => Topic started by: David Sutton on July 12, 2013, 09:56:00 pm
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A useful contribution I thought to the problem I sometimes get with blocked shadows. That and this post (http://www.luminous-landscape.com/forum/index.php?topic=80019.0)
As a result I've created some presets on my monitor to mimic the dynamic range of my favourite matte paper, and so far it works well..
It didn't take long to create a test print for density patches, and you are welcome to download it at http://davidsutton.co.nz/testprints/printingdensitypatches.jpg.
Cheers.
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Thank you for the test print.
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+1 to the thank you! I'm looking forward to trying this out on my printer, and not only determining end points to target in the files I send to print, but also comparing results among the several papers I enjoy using. Thanks again. --Barbara
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David, unfortunately the test image you've made available isn't correct.
Load it into PS and check the actual data and you'll see lots of inaccuracies; patch #2 = 1,1,1, Patch #13 = 15,15,15 patch#234 = 238,238,238 etc.
As the test is designed to pin down exact levels, to measure errors of 4 or greater make it not as useful as it should be.
Possibly this is a result of JPG compression, but a DIY uncompressed tiff isn't too difficult to make anyway.
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As a result I've created some presets on my monitor to mimic the dynamic range of my favourite matte paper, and so far it works well.
Yup (as I suggested) but the best way to do this is with a 'smart display system' like the SpectraView whereby you have full control over contrast ratio and you can build a suite of calibration targets.
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Scott Kelby says the black point should be set to R20,G20,B20.
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Scott Kelby says the black point should be set to R20,G20,B20.
Like most items under the subject of color management, Kelby hadn't the foggiest idea of what he's talking about.
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David, unfortunately the test image you've made available isn't correct.
Load it into PS and check the actual data and you'll see lots of inaccuracies; patch #2 = 1,1,1, Patch #13 = 15,15,15 patch#234 = 238,238,238 etc.
As the test is designed to pin down exact levels, to measure errors of 4 or greater make it not as useful as it should be.
Possibly this is a result of JPG compression, but a DIY uncompressed tiff isn't too difficult to make anyway.
Hello Rhyssydd. Yes , you are right! I didn't check the patches after making the conversion to a jpeg in Lightroom. Mea culpa. That makes the jpeg version useless.
I've uploaded a flattened version of the original tiff to the website: http://davidsutton.co.nz/testprints/printingdensitypatches.tif
The downside is it's now a 45mb file. Oh well.
Perhaps someone could double check that one for accuracy.
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Yes, they measure fine now.
My own version has a black background against every dark patch and all the white patches against base white. That way it's easier to judge where the thresholds are.
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My own version has a black background against every dark patch and all the white patches against base white. That way it's easier to judge where the thresholds are.
What a good idea. I've followed your suggestion and updated the file.
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David
Thank you for the update.
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Scott Kelby says the black point should be set to R20,G20,B20.
For what ?
As the article here points out the value changes with paper type/printer/profile.
The smart thing to do is use the chart David's provided, or one you've built yourself, and test for your own specific set up. It only takes a single sheet of paper. As the article mentions different papers can have significantly different threshold values.
Another interesting thing you can discover from the test is how much viewing light effects perceived shadow detail. You can target specific prints for their intended lighting conditions.
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Dear David,
Thank you for making this available. I look forward to testing my printer and favorite papers.
Jed
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For what ?
As the article here points out the value changes with paper type/printer/profile.
I may be missing something.....but, article where?
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I may be missing something.....but, article where?
Front page of Lula http://www.luminous-landscape.com/tutorials/beyond_calibration_2.shtml
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Front page of Lula http://www.luminous-landscape.com/tutorials/beyond_calibration_2.shtml
Thanks :-[
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Hi folks.
Glad to help out.
I'm sure I should know this but any idea why the conversion to a jpeg (from prophoto rgb) should mess up the patch luminance values?
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I'm sure I should know this but any idea why the conversion to a jpeg (from prophoto rgb) should mess up the patch luminance values?
JPG compresses the image data to make the data look like the original, it's not an exact replication. For the vast majority of image compression purposes rounding a value up or down by 0.4% makes no significant visible difference. The amount of data degradation can be controlled by the strength of the compression, but ultimately it's a lossy method.
In the case of charts where you need EXACT numbers JPG shouldn't be relied upon.
Having said that, I'm not sure I got it right anyway. When trying to build a chart from scratch here I found that the values set in the palettes weren't being put down correctly onto the canvas in PS CS4 anyway (at least in aRGB 8bit images). eg 8/8/8 dropped via the paint bucket measures out at 9/9/9 and just to complicate matters the pencil & brush tools deliver the correct values, and everything works as expected in 16bit mode. So it looks like there's a curious bug with the paint bucket tool in 8 bit I've stumbled on when it won't always paint the correct colours. I don't know if that's been corrected in later versions, but it's quite repeatable here.
The bottom line is that when building any test image that you want to use for determining exact values, double check what's on the page is what you expect it to be.
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David, thank you very much for the file. I am experiencing a problem with the color profile of the file you created. When I open it in Ps I see that it is tagged as Pro Photo. I then proceed to make a profile conversion to Adobe Rgb. The problem is that as a result the dark patches lighten up considerably. My knowledge is that if you do a "convert to profile" from Pro Photo to a 2.2 gamma color space you should not see any significant change in tonal values. But here I am seeing a difference. Am I doing something wrong or is this to be expected?
For anyone wondering why I want to convert it to Adobe RGB: I print from Lr to an Epson 3880, set to ABW mode, using a profile created with QTR software (I'm on Win7). Therefore I prefer to print a file that is already in a 2.2 gamma space, to avoid any possible problem arising from printing 1.8 gamma encoded data (I know that there should not be any issue because I am printing with a profile and not sending the data straight to the printer, but I still feel safer this way :)).
Cheers,
Luca
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David, thank you very much for the file. I am experiencing a problem with the color profile of the file you created. When I open it in Ps I see that it is tagged as Pro Photo. I then proceed to make a profile conversion to Adobe Rgb. The problem is that as a result the dark patches lighten up considerably. My knowledge is that if you do a "convert to profile" from Pro Photo to a 2.2 gamma color space you should not see any significant change in tonal values. But here I am seeing a difference. Am I doing something wrong or is this to be expected?
For anyone wondering why I want to convert it to Adobe RGB: I print from Lr to an Epson 3880, set to ABW mode, using a profile created with QTR software (I'm on Win7). Therefore I prefer to print a file that is already in a 2.2 gamma space, to avoid any possible problem arising from printing 1.8 gamma encoded data (I know that there should not be any issue because I am printing with a profile and not sending the data straight to the printer, but I still feel safer this way :)).
Cheers,
Luca
i might try Chart Throb to create my own 2.2 gamma step wedge.
http://www.botzilla.com/blog/archives/000544.html
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David, thank you very much for the file. I am experiencing a problem with the color profile of the file you created. When I open it in Ps I see that it is tagged as Pro Photo. I then proceed to make a profile conversion to Adobe Rgb. The problem is that as a result the dark patches lighten up considerably. My knowledge is that if you do a "convert to profile" from Pro Photo to a 2.2 gamma color space you should not see any significant change in tonal values. But here I am seeing a difference. Am I doing something wrong or is this to be expected?
For anyone wondering why I want to convert it to Adobe RGB: I print from Lr to an Epson 3880, set to ABW mode, using a profile created with QTR software (I'm on Win7). Therefore I prefer to print a file that is already in a 2.2 gamma space, to avoid any possible problem arising from printing 1.8 gamma encoded data (I know that there should not be any issue because I am printing with a profile and not sending the data straight to the printer, but I still feel safer this way :)).
Cheers,
Luca
Hello Luca. I would have thought that if you stay in 16 bit you shouldn't see a luminance change going to Argb. However the change to a 2.2 gamma may be a different matter, and I don't know enough to comment.
Sorry I can't help on that one.
Cheers,
David
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Hi David,
thank you for your feedback. I think I solved the issue by applying the profile, instead of converting it. The values remained the same.
Cheers,
Luca
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Hi David,
thank you for your feedback. I think I solved the issue by applying the profile, instead of converting it. The values remained the same.
Why would you want to do that? When you say "applying the profile", I assume you mean "assigning the colorspace". I think when assigning a Argb colorspace to a Prophoto-tagged image the original rgb values will not change, but the appearance of those values on screen will change. So when you print the image (in this case a Prophoto gray step wedge) the ABW printer is confused by the rgb values because they are Prophoto rgb values, which are 1.8 gamma values. The ABW was not designed for 1.8 gamma source files. It gets worse. When you try to match the print results to what you see on screen, you are essentially comparing rotten apples to rotten oranges. The print is rotten because the ABW misinterpreted the Prophoto-tagged image and the monitor screen is rotten because the original prophoto values are assigned a Argb colorspace for which is was not intended. I'm affraid you will have to create the gray target wedge from scratch inside the Argb colorspace before sending it off to the ABW printer if you want to compare apples to apples. Somebody correct me if I'm wrong.
read this:
http://ephotopros.com/articles/article-archives/articletype/articleview/articleid/156/assign-profile-vs-convert-to-profile.aspx
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Hi texshooter,
when I assign Adobe RGB the values do not change, patch 1 still reads R1G1B1 and so on. If I instead convert to Adobe RGB the values change (20 becomes 35 for example). Therefore It makes sense to me to assign the profile before printing. The purpose here is to check printer performance at the extreme tone levels, so I want to be sure to send the correct tone values to the printer avoiding any possible conversion.
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"when I assign Adobe RGB the values do not change, patch 1 still reads R1G1B1 and so on. "
>That may be true, but the file is still 1.8 gamma. You don't want to feed the ABW driver 1.8 gamma.
"If I instead convert to Adobe RGB the values change (20 becomes 35 for example). "
> That may be true, but at least it would be 2.2 gamma.
"Therefore It makes sense to me to assign the profile before printing. "
>Weren't you trying to avoid sending the ABW a 1.8 gamma file?
"The purpose here is to check printer performance at the extreme tone levels, so I want to be sure to send the correct tone values to the printer avoiding any possible conversion."
>I don't think printer drivers can interpret "assigned" colorspaces. the file needs to be "converted" for the new colorspace to be seen by the printer. Assigning doesn't change the file, it only changes the display.
Any help from the heavyweights?
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For what ?
As the article here points out the value changes with paper type/printer/profile.
The smart thing to do is use the chart David's provided, or one you've built yourself, and test for your own specific set up. It only takes a single sheet of paper. As the article mentions different papers can have significantly different threshold values.
Another interesting thing you can discover from the test is how much viewing light effects perceived shadow detail. You can target specific prints for their intended lighting conditions.
I think the writer of that article should have mentioned calibration/linearisation first in that article. With a printer/ink/media preset/paper that does not have that condition you could be wasting potential dynamic range and time when you adapt the methods described. Where analogue print making had a somewhat linear range (neg+pos) or at least a continuous one between the thresholds it does not have to be like that with inkjet printing.
The viewing/display light conditions was what I missed in that article too. I checked for framing behind glass and viewing light, both can cause the shadows to block even when the paper's dynamic range is wide enough. In a sense a paper linearised for the printer and its inks already meets the threshold conditions he describes, the (B&W) printer profile made of that condition should be enough. Enough viewing light should match that. It is in the display condition and display light conditions that shadows still can block. If viewing light is adapted to the expected display conditions one can correct the shadows and more with curves based on a proof print or a print of the targets discussed and add a curve like that to the print filters of Qimage for example. Image content should not be forgotten in that phase. I do not think a curve based on the targets + the adapted soft proof replaces a real proof print, it helps though.
Several 21 step wedge images have short expanded shadow + highlight ranges next to the main one. Can not recall where I got the "Technical" one from but it has the 21 step next to a continuous one and shadow + highlight ranges + 4 well chosen images. B&W all. A print made with it after linearisation/profiling tells a lot in different viewing conditions.
There is also a bit of confusion created by the writer. 90% of photographers have a workflow that uses RGB-device printer profiles. There is an RGB>CMYK translation in all the workflows but it does not happen in the RGB-device printer profile for most. Media presets have that translation or part of it baked in. With a RIP the printer profile usually holds way more of the RGB>CMYK translation so for that condition he is right
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Met vriendelijke groet, Ernst
http://www.pigment-print.com/spectralplots/spectrumviz_1.htm
July 2013, 500+ inkjet media white spectral plots.
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I think the writer of that article should have mentioned calibration/linearisation first in that article.
I'm not sure that article was aimed at photographers that have printers where linearisation is an option, that's really only possible on professional wide format printers.
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I wrote "mentioned" as I did not expect that every reader of that article could go that route though we have seen that at least for B&W all kinds of DIY solutions have been found. For the users the writer could explain that today's desktop printers are already quite well linearised/profiled for the OEM papers and I wonder what this method improves on that. It will improve on that with the knowledge of viewing light - display conditions you mentioned already but that chapter was not touched. It will also correct somewhat the use of third party papers that do not fit the OEM media presets + their profile correctly.
Met vriendelijke groet, Ernst
http://www.pigment-print.com/spectralplots/spectrumviz_1.htm
July 2013, 500+ inkjet media white spectral plots.