Colour Management For Printing.

[barfl2]

Thank you Grandad35 for your detailed post. I had previously downloaded some of Norman Korens articles together with test images from Colour Collective/Digital Dog etc.

These images have been printed out on 6x4 and A4 on various papers and I have written my comments on the back. A couple were in my limited knowledge very good, so in a way you are right I already have a printer/paper setting obtained from a high quality image. They were all straight prints, I did not vary the colours only choosing different paper settings. If you start tweaking colour settings as well it could be endless.

However these tests were done some time ago and before I carried out my monitor calibration. I will need to repeat the exercise and hopefully my monitor will be close.

Without a spectro I suppose thats about the best you can hope to achieve. Keen amateurs and professionals will obviously go down that route. However as you rightly point out it is a very complicated subject.

 

[Grandad35]

It is interesting that LCD monitors may have up to 16.8 millions colors for 100% NTSC Color Gamut but the human eye can distinguish up to 10 million.

Yes, but we don't always need that many colors for our brains to "see" a decent image.
The first image has all 16,777,216 colors available while the second version only uses 512 colors (click to enlarge).

The second was generated from the first in PS using two "Levels" adjustments - its histogram is shown below. Because there is enough dither in adjacent pixels to generate different color combinations, our eyes blend these pixels to generate the intermediate colors. The thumbnail to the right of the histogram shows a screen capture of a magnified area to show that the individual pixels are very different from each other.

Lest you be left with the impression that we can get away with far fewer colors in every case, the sky in this photo shows that this technique fails miserably in areas with smooth gradients (like the sky or certain areas of the rock face).

 

[Grandad35]

Without a spectro I suppose thats about the best you can hope to achieve. Keen amateurs and professionals will obviously go down that route. However as you rightly point out it is a very complicated subject.

Fortunately, you don't need to buy a spectro - all that you need is to have someone generate a printer profile for each printer/ink/paper combination that you use. For example the forum member "Smile" (see post http://www.printerknowledge.com/threads/inkjet-vs-laser-for-art-prints.8314/#post-65101) provides such a service in Europe. A web search for "printer profile service" will turn up other sources in your area.

The discussions on number of patches, how they are used, etc. only apply if you are going to generate your own profiles.

If you determine that you are satisfied with the printed colors after your tests, then you don't need custom profiles.

 

[stratman]

Yes, but we don't always need that many colors for our brains to "see" a decent image.

Good stuff, Granddad35! Probably a consideration in why many monitors are less that 100% NTSC Color Gamut.

Many critters see less colors than we and seem to do just fine in the Wild. Of course some critters see other spectrum of electromagnetism than visible light which gives them an advantage in certain circumstances. Still we're pretty darn fortunate to have rods and cones. (no relation to forum member rodbam)

 

[Roy Sletcher]

Laptops are notorious for poor color reproduction. It’s a good sign that the colors on your Asus monitor didn’t change much after calibration, but colors drift with time. I have an old CCFL/LCD monitor that lost half of its blue illumination after 3 years, and it had to be recalibrated every few weeks. My current LED/LCD monitor is showing very little degradation over time.

When you walk through a large electronics store have you ever noticed how the colors on the various displays are different, even though they are connected to the same video feed? This is the issue addressed by calibrating your monitor. If every display in a store was calibrated, they would all show the same colors. Once your monitor is calibrated, you can send a photo to anyone else with a calibrated monitor and be assured that they will see the same colors that you see. More importantly, a photo displayed with the correct colors on your calibrated monitor can be sent to any color managed printer and you should get a pleasing print. Getting your monitor calibrated is necessary to achieve a color managed workflow, but it isn’t sufficient – that’s where getting your printer profiled comes in. The “patches” discussed in other posts are small color samples that are used to generate a printer profile, and have nothing to do with calibrating your monitor.

Wrapping your head around color management is not a trivial exercise. The various articles on this link will give you a cursory understanding of the subject, if you are so inclined. I have included a few screen captures to illustrate why getting your printer to match your monitor isn’t a trivial exercise. The first image shows the range of colors (aka gamut) in the sRGB color space (solid) and the range of colors that my LED monitor can display (wireframe). Note that the monitor can display more colors than the sRGB color space, but that there are some small areas where it can’t display the entire range of colors. It shouldn’t be surprising that this is the case, since the sRGB color space was initially defined to match high end monitors in 1996.

The second image shows the gamut of my i9900 (8 color inkjet) printer (solid) against the monitor (wireframe). This is why I stated previously that there are lots of colors that you can show on your monitor that can’t be printed by your printer. It also shows that there are lots of colors that can be printed, but which can’t be displayed on your monitor. In addition to getting the correct colors in the areas where the two gamuts overlap, the printer profile must also handle what to do with colors that can be shown on the monitor but which can’t be printed. That’s where rendering intents come in.

One final point – there are LOTS of colors that we can see that are outside of the range of colors available on our monitors. The last image shows the same sRGB color space (solid) compared to a high end DSLR (wireframe). That’s why many people use larger color spaces (e.g. aRGB).

View attachment 218 View attachment 219 View attachment 220

I would rationalize your statement in para two: " Once your monitor is calibrated, you can send a photo to anyone else with a calibrated monitor and be assured that they will see the same colors that you see." This is dependent upon the quality of the recipients and senders hardware. For example as you say budget level laptops are notorius for poor colour, often only having a 6 bit data path. If you send an image to somebody with that level hardware they will see a very different image if you the sender have a higher quality monitor, even though both are calibrated to the best their specs will allow.

I have two monitors on my desk. One wide gamut - supposedly full aRGB, and the a second a budget level covering the sRGB colour space, and the difference is visible.

Anybody who submits digital images to competitions always has this worry about how well they will be displayed for the judges.

I see a lot of comments from committees and organisers implying the problem is solved if a consumer level calibration is carried out befoer the display. My eyes tell me there is more to it.

Just sayin'.

RS

 

[Grandad35]

...<snip>....If you send an image to somebody with that level hardware they will see a very different image if you the sender have a higher quality monitor, even though both are calibrated to the best their specs will allow.

You are, of course, absolutely correct. I agonized about how much detail to get into and whether too much detail would only confuse the OP. How do we take a subject that takes a book to cover and still give a helpful and (at least somewhat accurate) 1 paragraph answer?

For example, in addition to the point that you raised about the quality of the monitor, there are also the issues of whether to calibrate at a white point of 5500 or 6500 deg K, what white luminance value to use, what ambient light level to use and even what color to paint the wall behind the monitor. However, for a casual user all of these effects are minor when compared to the errors caused by a typical uncalibrated monitor. For a professional, that would not be the case, and the other factors would need to be addressed.

 

[Roy Sletcher]

You are, of course, absolutely correct. I agonized about how much detail to get into and whether too much detail would only confuse the OP. How do we take a subject that takes a book to cover and still give a helpful and (at least somewhat accurate) 1 paragraph answer?

For example, in addition to the point that you raised about the quality of the monitor, there are also the issues of whether to calibrate at a white point of 5500 or 6500 deg K, what white luminance value to use, what ambient light level to use and even what color to paint the wall behind the monitor. However, for a casual user all of these effects are minor when compared to the errors caused by a typical uncalibrated monitor. For a professional, that would not be the case, and the other factors would need to be addressed.

Hi Grandad,

Understand and agree with your comments. I was not trying to "pick nits" as this subject gets complicated quickly, and my knowledge is only sufficient to keep my setup on track with consistent or standardised colour output that I can predict and duplicate. Learning about colour management has reduced my "WTF?" moments and now when a bizarre result comes out of the printer I can usually diagnose, trouble shoot, and rectify the defect. Saves a lot of time, frustration, paper, and ink.

The real tragedy is the amount of misinformation and downright incorrect statements made in many forums and websites by people posing at experts. Ah yes the "internet syndrome". I was led down a few rabbit holes in previous years until I figured only a small percentage of people posting on this subject knew what they were talking about.

RS