Profile Assessment

[RogerB]

As mikling says, this is a tough test for any printer, especially one with only a single black. If the actual print matches the Gamutvision simulation then your primary profile may be quite acceptable. You've said yourself that it's downhill after that, and I wouldn't be too happy with the later iterations. Time to make a few prints and do a subjective evaluation I think. I can say that it's definitely possible to make reasonable B&W prints with the "9000-type" printer. Many years ago I had an S9000 (grandad to your Pro 9000 II) and with my own custom profiles my B&W prints were good enough to compete in camera club competitions.

As for evaluating the colour quality, a good start is the Macbeth Colorchecker. All the colours should be in-gamut and even a visual comparison with the real thing will give you a good idea of the accuracy. You can of course measure the printed colours with your Colormunki, but I think you would have to use Argyll for that. For a subjective test of profile "smoothness" the Grainger rainbow is always good. Very unforgiving of nasty colour transitions. Time to move into the subjective realm I fear.

 

[crenedecotret]

One thing that might be considered is each time you make a reading, you will get a different reading, that's simply a fact with all devices. If you are doing this with the Colormunki, I suspect that you are taking readings that incorporates data from previous readings in the optimization process. This in itself might be a factor in your struggles and one reason why the original appears to be better.
Why? because spectrophotometer sensors need warm up time and there is also drift involved. When you take readings gathered from different times, it is possible that the readings themselves are part of the error. If you had taken all readings each time in one batch then there might be better relative consistency between the readings which is critical in B&W. This might or might not be a shortcoming of the color munki process or strategy. In non critical situations the different read times of the sensor might not be a big factor but when you come to trying to linearize B&W, that could be an issue. I don't know.

The other aspect is the color munki device itself. Its' design allows stray light to affect the readings taken as opposed to the more expensive models from Xrite where this aspect is recognized and a different design is used. I suspect intuitively that the stray light may have more influence in B&W data readings.

Lookup the average command in argyll... you can take multiple readings and have Argyll combine them.. I'm not sure it's worth the effort if you are content with a profile but it can be worth a try in those cases where your results are less than ideal

 

[Emulator]

RogerB, I have put my "subjective" hat on, but have been distracted by domestic demands. The process also needs some thought. I will be back; for older viewers, imagine a goldfish swimming round in a glass bowl.

 

[Emulator]

RogerB

I have printed the black to white 360 degree radial gradient image using the ColorMunki primary and four optimisation profiles on a single A4 sheet of Sihl glossy micro porous 280g/sm paper, this required five passes of the paper.

The Canon Pro9000 II printer with IS inks, was set to Photo Paper Pro Platinum, as it was for the generation of the profiling charts.

Unfortunately I haven't got a scanner of acceptable quality, that would enable posting of the images in a meaningful way.

I was wondering if I posted (by RoyalMail) the sheet to you, whether you have a scanner that would do the job, at least you would be able to pass judgement on the print.

 

[RogerB]

By all means mail me the prints, but the big question is, "how do they look to you?" Can you see any colour bands or density bands in the gradients?

 

[Emulator]

OK, I will mail the A4 sheet tomorrow. I am not going to influence your subjective judgement, by giving my view!

I thought it would be interesting to have a group subjective view by asking members to identify the images and relate them to the profiles based on the data in the earlier posts. That is if you are satisfied with the image file being a good representation of the print and you can post it up on the forum as is. See if you can determine the profile printing order.

I will explain when you have the image posted and provide the answers after about a week.

 

[RogerB]

OK, I will mail the A4 sheet tomorrow. I am not going to influence your subjective judgement, by giving my view!

I thought it would be interesting to have a group subjective view by asking members to identify the images and relate them to the profiles based on the data in the earlier posts. That is if you are satisfied with the image file being a good representation of the print and you can post it up on the forum as is. See if you can determine the profile printing order.

I will explain when you have the image posted and provide the answers after about a week.

Well, I've scanned your composite print and thrown a Colorchecker in for good measure. Here's how it looks. (I have added the numbers in PS but otherwise this is un-processed)

And to make it a bit easier (maybe) here's a composite of the centre section of each print.

I have to say that as far as smoothness goes these are pretty good, with very little difference between the five prints. Definitely hard to see any difference in the scanned image.

Looking at the prints in real life with an illumination of about 1000 lux I can see banding in the darkest tones, but it's relatively slight. For me, the best is #3 and the worst #5. Any other views?

 

[Emulator]

Thanks Roger, you have a good scanner! I was wondering if it is worth buying a cheap (about £60 at Amazon) Epson V37 or Canon LiDE 210, or is it a waste of money for this sort of thing?

I was surprised at the result myself and having given it a few days thought, have an idea why the Gamutvision predictions and the print are slightly different.

When I produced the set of primary and optimised profiles, I deliberately left the profiling charts to rest, overnight before reading them into ColorMunki. The time interval would have been between 12 and 24 hours. I am not convinced that the standard CM 10 minute waiting period is anywhere near long enough for the micro and nano-porous papers.

The Sihl paper used is undoubtedly a good microporous, instant dry, paper, but it does mature noticeably over a few days after printing.

The gradients print showed more noticeable rings when freshly printed, but these all faded away significantly after about 36 hours.

So I think the Gamutvision test is showing the amounts of ink laid down. But the paper characteristics, which were allowed to take effect in the waiting period before the charts were read in CM, matured the ink absorbtion into a good print rersult.

(Why the print size has changed, I do not know)

 

[RogerB]

Thanks Roger, you have a good scanner! I was wondering if it is worth buying a cheap (about £60 at Amazon) Epson V37 or Canon LiDE 210, or is it a waste of money for this sort of thing?

I suspect that scanner technology is so mature that most will give a decent result these days. Even the AIO's seem to be pretty good. However, I wouldn't want to rely on a scanner of any kind for measurement purposes.

I was surprised at the result myself and having given it a few days thought, have an idea why the Gamutvision predictions and the print are slightly different.

When I produced the set of primary and optimised profiles, I deliberately left the profiling charts to rest, overnight before reading them into ColorMunki. The time interval would have been between 12 and 24 hours. I am not convinced that the standard CM 10 minute waiting period is anywhere near long enough for the micro and nano-porous papers.

The Sihl paper used is undoubtedly a good microporous, instant dry, paper, but it does mature noticeably over a few days after printing.

The gradients print showed more noticeable rings when freshly printed, but these all faded away significantly after about 36 hours.

So I think the Gamutvision test is showing the amounts of ink laid down. But the paper characteristics, which were allowed to take effect in the waiting period before the charts were read in CM, matured the ink absorbtion into a good print rersult.

(Why the print size has changed, I do not know)

There has been a lot of confusion about drying times, whether canvas should be profiled before or after coating etc etc. The fact is that the profile represents the state of the printed target at the time the measurement was made - it really is a snapshot. The profile doesn't contain any information about how the target was printed or how it changes over time. The Gamutvision results can only tell you the state of the print at the time your snapshot was taken.

It's well known that dye inks take some time to stabilise and I would say that a 10 minute drying time is far too short for dye inks. If you were to measure the target after 10 minutes the resulting profile would (should!) give corect colours in prints 10 minutes after they leave the printer. Any susequent changes (stabilisation) would reduce the accuracy. If as you say, the Sihl paper does " mature noticeably over a few days" then for the best profile you should be measuring the target after a few days, not a few minutes.

Unfortunately what we are looking at here are small deviations from pure grey - errors according to Gamutvision of less than 2 DeltaE. Errors of this size are not always easy to see unless they occur over small regions, that is if they change rapidly with L*. To my eye the area in which there are the most rapid changes is in the dark tones. This is the area of maximum ink loading, where the dark grey is made almost entirely of CMY inks, so it's not surprising if the maximum errors are here. Nor is it surprising if the appearance of the print changes most in this area after printing.

I think you have done quite well with this profile. Maybe you could do a bit better if you could con the CM into leaving the print for a few days before measuring the target. Perhaps other CM users can tell you how to do that. Of course you could always use Argyll, then your options are almost limitless!

 

[Emulator]

I suspect that scanner technology is so mature that most will give a decent result these days. Even the AIO's seem to be pretty good. However, I wouldn't want to rely on a scanner of any kind for measurement purposes.

Does this mean you think the Gamutvision Print Test image which is read by scanner and used by Gamutvision to analyse the printed colour errors is not worth pursuing?