Luminous Landscape Forum
Raw & Post Processing, Printing => Colour Management => Topic started by: Doug Gray on September 20, 2017, 11:13:53 pm
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I created an ISIS2 target image in sRGB with a set of 380 different LAB color patches. Each color was from the range of L* of 10 to 90 and a* and b* in increments of +/- 10. All possible 10 unit delta colors were initially created then all that were outside sRGB removed. The remaining were sifted through various profiles with and without OBAs using M1 and M2 profiles to find a set of colors that could all be printed witha Delta E < .5 when roundtripped through the profile set. Profiles for both the 9800 and 9500 were used.
The purpose was to create a set of colors in sRGB that were all printable on both printers with a variety of glossy paper.
Then the ISIS2 target image, in sRGB, was printed using various modes of Photoshop Managing and Printer Managing color. The prints were then scanned with the ISIS2 and the LAB results were used to create an exact image of the printed scans. However, some patches and printer modes did not keep the patch colors within sRGB (nor are they required to) and, in some cases many colors actually printed from the sRGB target exceeded even Adobe RGB. As a result, the attached image is in a ProPhoto, 16 bit tiff so all printed colors can be properly imaged. Each scanned image occupies a named layer in the tiff file which can be downloaded and viewed in Photoshop. Loading the tiff file in Photoshop allows one to select and alternate the printed images so it's easy to compare say, The Canon default driver with the Reference LAB image or a custom profile's Perceptual rendering. In all cases the default driver settings, together with "Printer Manages Color" significantly boosted luminance and, particularly for the Canon, Boosted saturation where the printer gamut allowed by extremely large amounts.
If you set the info panel display for LAB and 32 bits it will display high precision LAB values at the cursor. But make sure you are operating at 100% or increments of 100% zoom. Photoshop has a small bug with fractional zoom levels and precision levels deteriorate to 8 bits in some cases.
It's interesting to see just how much the L* is bumped for the defaults when "Printer Manages Color" is used. A requested L* of 50 prints at 60 in many of the Canon 9500 II settings. The gray patches at the end of the chart are fillers to make ISIS happy and they are all at LAB (50,0,0). Mouse over them to see the boost. Compare that to the custom I1Profiler profile print.
The attached image contains:
Lab10 Reference
9800 Photoshop Manages, Custom Absolute
9800 Photoshop Manages, Custom Perceptual
9800 Photoshop Manages, Perceptual
9800 Printer Manages Defaults
9500 Photoshop Manages, Absolute
9500 Printer Manages, ICM Absolute
9500 Photoshop Manages, Perceptual
9500 Printer Manages, ICM Perceptual
9500 Printer Manages defaults
9500 Printer Manages defaults, Vivid Color
Also included is an attached image for the Lab Reference target in sRGB.
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For the Canon 9500 II using the default driver, here's a list of the top 5 colors that are increased in saturation beyond the sRGB gamut. The first 3 columns are the requested color in LAB. The next 3 columns are the actual printed color values in LAB. The last column is the amount the saturation increased. sqrt(a^2+b^2) increase.
40.0000 -20.0000 -20.0000 46.8200 -32.7900 -31.9700 17.5116
50.0000 -30.0000 -10.0000 55.2400 -40.1900 -24.0700 15.2238
50.0000 -20.0000 -20.0000 58.1900 -29.8500 -28.0400 12.6701
40.0000 -20.0000 -10.0000 48.6200 -29.0900 -19.2500 12.5218
60.0000 -30.0000 -20.0000 61.5900 -37.4800 -30.3300 12.1592
So that's where the "pop" comes from letting the printer manage color for snapshots processed in sRGB.
When "vivid color" is selected the effect is amplified as expected.
50.0000 -30.0000 -10.0000 50.7300 -57.4400 -30.0500 33.2028
40.0000 -20.0000 -20.0000 41.9200 -42.8100 -40.5200 30.6612
40.0000 -30.0000 0 41.9900 -57.5000 -14.7400 29.3592
60.0000 -30.0000 -20.0000 56.6100 -51.2200 -39.1100 28.3889
40.0000 -20.0000 -10.0000 43.1600 -42.7500 -26.3700 27.8682
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Mac and Windows behave the same?
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Mac and Windows behave the same?
Good question. Does anyone have experience with Printer Manages Color using the same printer and Photoshop settings with Mac and Windows? It's up to the writers of the printer driver and I would guess they would want them to match. Probably most do. One thing's for sure, they don't match across brands and likely across at least some models.
One thing going through the layers and their differing colors illustrates is that there is no way to use soft proofing in Printer Manages default modes*. The differences, even between their canned profiles and their default are too stark. But then it seems people advocating letting the printer manage color don't find value in soft proofing. It's print and hope. Whatever makes them happy. I rather like soft proofing and have made an effort to get it right. Even though it's not perfect it's quite close. Perhaps I'm lucky and my eye's spectral response is close enough to the Standard Observer.
*At least my 9800 can do a proper job in Printer Manages selecting the ICM mode, input RGB profile and output printer profile/RI. But that doesn't offer Relative w BPC and I'm not prepared to give that up.