I’m the biggest monitor calibration evangelist you’ll ever meet, and I’ll gladly preach at you until your ears bleed about why you must calibrate your monitor.
But, I have to admit that calibration presents a couple of problems for people with small-gamut screens. (I’m mainly talking about laptop screens, but other low-end LCDs are affected too.)
Some of the relevant scientific concepts are brain-melting, and far beyond my understanding. I will simplify the main concepts to a level which I understand, and I hope other colour-management novices will be able to make sense of it too.
There are two problems arising from calibrating a small-gamut monitor:
1. Detail disappearing from bright colours
After calibration, you might find that subtle highlight detail in your vivid floral photos has turned to flat "bleh".
2. Blues turning purple
It’s very common to hear the lament "I calibrated, and now everyone’s blue jeans are purple!" If you’ve had this problem, you’ll know exactly what I’m talking about.
The bitter irony is, these problems only exist in Photoshop and other colour-managed applications. If you view your images in a "dumb" program, your blues will look blue, and your bright colours will look fine.
This can lead users to throw up their hands in despair, and shove their monitor calibration device in a cupboard (or on eBay).
Calibration is not the culprit
Poor old calibration gets a bad rap – it’s not his fault.
The process we commonly call "calibration" is actually two processes – Calibration and Profiling.
- Calibration is the physical adjustments we make to the monitor (most commonly Brightness) with or without the guidance of the calibration device.
- Profiling is where the device analyses your screen and records a description of its behaviour, then saves this description as an ICC Profile. Photoshop then consults this profile in order to properly display your images.
The trouble is, Photoshop uses this profile a little too well, as we’ll see.
I’d love to show you some examples …
… but it’s no use. If I posted a photo of a blue sky, for example, it would look blue to some of you, and purple to others.
It would all depend on the particular idiosyncracies of your monitor, not to mention the web browser you’re using.
But if you’re reading this article, I figure you know what the problems look like anyway! Let's talk about them ...
Problem 1: Flat colours
It’s all about Gamut
Gamut is the word we use to describe a range of colours.
Of the standard RGB colour spaces, sRGB has the smallest gamut, Adobe RGB has a somewhat larger gamut, and ProPhoto RGB has a ridiculously enormous gamut.
High-end monitor manufacturers like to reference the Adobe RGB gamut when boasting about their flagship products. If you visit the Eizo or NEC websites, you’ll see claims of "92% of Adobe RGB", "98% of Adobe RGB", etc.
What we never hear about is comparisons of normal monitors to the sRGB gamut. And you might be surprised.
To my understanding, the sRGB colour space was created last century to represent the average gamut of the imaging devices of the day, including CRT monitors. (Remember them?)
Like many people, I assumed that modern LCD monitors, with their amazing Contrast Ratios etc, must have far superior gamuts to those old dinosaurs. Turns out I was wrong!
The truth is, some LCD monitors have gamuts that don’t even come close to sRGB. And laptops are among the worst.
Check your monitor’s gamut
There’s a quick way to see how your monitor’s gamut compares to sRGB. (Please note this is not a precise scientific test, just a rough visual guide).
First, right-click and save this file, then open it in Photoshop.
These eighteen strips represent each of the six spectral colours fading to white, black and grey.
Open the Custom Proof Setup dialog:
"Device to Simulate" is your monitor profile (mine is called "6500_2.2_100_Eizo"). Turn off "Preserve RGB Numbers".
(These screenshots are from CS2. The dialog differs slightly in other versions, but it should translate ok.)
Now turn on the Gamut Warning:
Wherever you see grey patches, that’s the parts of sRGB that your monitor can’t show properly. Here’s my laptop test:
Wow! My laptop falls badly short of the full sRGB gamut.
And for comparison, here’s my mid-range Eizo monitor:
Interesting, huh? Even a monitor which cost me more than my first car doesn’t fully encompass the sRGB gamut. Notice how blues and magentas are the worst.
How does your monitor compare?
What does this mean?
In short, it means that if any of these extreme colours occur in your image, your monitor doesn’t have the gamut to display them accurately. That’s the key word here – "accurately".
Let’s not get too uptight
Let’s face it, the above test is hardly comprehensive. There’s no skintones, or trees, or bridesmaids’ dresses, or family pets. All we’ve tested are the really extreme colours, which (thankfully) don’t occur in nature very often. Your day-to-day photographs won’t present a problem at all.
But if you do photograph some very vivid colours, or if you get a bit heavy-handed with Saturation in Photoshop, you might find that you can’t see detail in the brightest areas.
It’s been fairly well documented that Photoshop’s Gamut Warning feature is not particularly accurate. Those grey areas can only be considered a rough guide at best. But that’s all we need.
Is this problem the same as Channel Clipping?
Only vaguely. Channel clipping is where one of the channels has reached the 255 value, so detail in that channel is lost. That problem can be faced by anybody, regardless of their monitor.
A small-gamut monitor presents a different problem. It can make your channels appear clipped even when they’re not.
Ok, so how does Photoshop display colours?
Let’s take a look behind the scenes …
Colour-managed programs show your colours using the Relative Colorimetric rendering intent. I won’t bore you with stuff about rendering intents (Google will give you plenty of info), but basically, it means that all colours that are within the screen’s gamut are shown accurately, but any that are out-of-gamut all get flattened off to the nearest available in-gamut colour.
Gobbledegook? Let’s try a diagram:
If the triangle is the gamut of our monitor, and we’re viewing a photo with some very bright greens, what will we see?
Well, we’ll see Colour A accurately, and we’ll see Colour B accurately (although only just!), because the monitor is capable of them. But Colours C and D will look the same as Colour B, because out-of-gamut colours simply get mapped to the nearest available in-gamut colour.
So, when you look at the photo on your screen, all you’ll see is a flat area of Colour B, but somebody with a better screen will be able to see the different shades of B, C and D.
Or, try this explanation:
On the left, we have a graph of reds in a photo – from no red at all to very bright red.
On the right, we have those reds displayed on a small-gamut monitor. The brightest reds are too bright to display, so they get "chopped off".
How do non-colour-managed viewers show colour?
Before you calibrated, you could see all the detail in a super-saturated image. Even after you’ve calibrated, you can look at your image in Internet Explorer, or Windows Picture Viewer, or some other "dumb" program, and see all the detail.
This makes you want to yell "Aaaaaaaaargh!!!", and throw your calibrator in the bin.
Why can simple programs show what Photoshop can’t? Well, it’s simple. They do this:
They squash down all the colours to fit the screen’s gamut. All the colours are now visible, but they’re all wrong. Not just the bright colours – all the colours.
How wrong are they? Well, that depends on your screen. Some screens are pretty good, others are woeful.
So, here’s your choice:
- On the one hand, you can remain uncalibrated, and see all the brightest detail in your photos, but never know if your colours are correct.
- On the other hand, you can calibrate, and enjoy correct colours most of the time, but work blindly when you have super-saturated colours.
Pretty crappy choice, huh? Sorry, but that’s just how it is.
But, as I’ve been saying all along, it’s not as big a problem as it seems. Most photos won’t challenge your monitor’s gamut in the slightest. So it won’t surprise you when I say: "Calibrate, friend, and enjoy the accurate colours in 99% of your photos."
Problem 2: Blues turn purple
Up to this point, I’ve been fairly sure of my facts. From here onwards, I get very hazy.
If you do a Google search, you’ll find that many people are having problems with purple blues on their laptop screens.
But explanations for the problem are harder to find, and when you do, they’re damned hard to understand. Plenty of jargon about Lookup Tables, 3D colour modelling, etc, which makes your eyes water.
I can’t offer a scientific explanation, and I certainly can’t offer a solution – all I’ll try to do is explain it in the very simple terms that my own meagre brain can comprehend.
Ok, so I lied
Higher up the page, I told you that if your monitor is calibrated, you’ll have trouble with out-of-gamut colours, but your in-gamut colours will be accurate.
This isn’t completely true. In fact, it’s only five-sixths true.
Your Magentas, Reds, Yellows, Greens and Cyans will be accurate … but not your Blues. They’re likely to look purple.
Why? Oh God, why??
It’s as frustrating as hell, isn’t it? Purple skies, purple jeans, purple policemen … heck, the headings on this web page probably even look slightly purple to you.
The reason for this, in my frail understanding, lies deep in the inner workings of the L*a*b* colour space.
(Photoshop simply calls it "Lab", so I will too.)
A little bit about Lab
In most colour-managed environments, Lab is the "Profile Connection Space" which translates from one profile to another. If a Frenchman was trying to explain something to you, but he didn’t speak English, you’d need an interpreter, right? The Frenchman would talk, the interpreter would translate, and you’d understand.
Well, in this case, the image is trying to explain its colours to you. It speaks the language of sRGB, or Adobe RGB, or whatever. But you only understand the language of your monitor. Luckily you’ve got Lab to translate for you.
He’s quite a shy guy – he hides in the back room of Photoshop, and you don’t often see him unless you go looking. But he’s very busy, translating every single pixel that you see.
He’s also a very nice, polite guy – he doesn’t drink, or smoke, or gamble. But he has one vice – his blues are all bent out of shape!
Now, I really don’t understand this, but here’s what I’ve gleaned:
PLEASE NOTE: This diagram is not in any way to scale!
Remember our discussion about out-of-gamut colours earlier? We talked about greens, and how as they got more saturated, they wandered further away from your monitor’s gamut, and had to be pulled back.
Well, in Lab mode, most of the other colours "wander" in roughly a straight line as they get more saturated. But our friend Blue wanders off towards Magenta, before eventually veering back to his destination.
I don’t understand why, so don’t ask me. He just does!
What this means for us
Remember our greens? Colours C and D were too saturated for our monitor, so they got pulled back to sit with Colour B.
Blue is not so well-behaved:
If out-of-gamut Colour A was brought back to gamut in a straight line, he’d end up at point b, and that would be fine.
But instead, he follows his trail of breadcrumbs back to point c, which is over near Magenta. And so we see purple. D’oh!
On better monitors …
For monitors with a larger gamut, it doesn’t matter, because Colour A is already within the gamut, so no re-mapping has to occur.
Are there solutions?
If you’ve read this far, you must be thinking "C’mon Damien, tell me how to fix these problems!"
I don’t have much good news for you, I’m afraid.
The only real solution
Buy a better monitor. Sorry, but at this stage, I don’t know of any other fix.
If you own a laptop, this would mean setting up an external monitor for your editing (and that introduces some system/calibration complexities which are a hassle too.)
If you own a desktop, you can simply upgrade your monitor, and maybe use your old one as a second screen for your palettes etc. (That’s what I’ve done, and I love the extra real estate!)
I’m not saying you’ll have to spend a fortune. Any better-than-average monitor should serve you well. Of course, the more you spend, the better it will be.
A future solution?
In the future, somebody might develop a colour-management system that doesn’t rely on Lab as its Profile Connection Space. This would solve the purple blues problem, at least, though not the colour-clipping.
Hopefully, as time goes by, all monitors will have larger gamuts, so our problems will disappear anyway.
In the meantime …
Flawed workaround #1
To see the detail in the very bright colours that your monitor can’t show, you can partially desaturate.
Make a Hue/Saturation adjustment layer, and nudge the Saturation slider to the left until you can see shape and detail in your super-bright colours.
Why might you do this?
To visually check that the detail is really there. If you desaturate, and it’s still a flat, featureless area, then it was probably a channel clipping problem rather than a monitor problem.
This method won’t help your purple blues – they’ll still be purple, just less saturated.
For God’s sake remember to turn that Hue/Sat layer off before output! You certainly don’t want to print a desaturated image.
Remember, just because your screen has trouble with some bright colours, doesn’t mean that you printer will too. Some colours are more easily reproducible in ink than on screen.
Flawed workaround #2
If you open Photoshop’s Color Settings, and enable the Advanced Options, you’ll find a setting down the bottom to "Desaturate Monitor Colors by: 20%"
This seems mis-named to me. What it really does is desaturate all the colours in Photoshop – not only images, but colour palettes etc as well.
You might need more or less than 20%, so try it and see.
Why might you do this?
Exactly as I mentioned above – this is a way to check if detail exists in super-saturated areas of colour. Again, it won’t help your purple problem.
This method is slightly superior to method 1, because it doesn’t affect your image at all – no data is changed. But it’s still a pretty clumsy approach.
Immediately you activate this setting, nothing you see is quite accurate. Under these circumstances, it would be very easy to unwittingly over-saturate some colours, only to be shocked at the results when printed.
If you try this method, I strongly recommend you only do it temporarily to check for detail, then turn it off again.
Flawed workaround #3
As we discussed, it’s the monitor profile that causes these problems. Colour-managed programs like Photoshop use the profile, so that’s where you see the problems.
There’s a way to view images in Photoshop without being altered by the monitor profile. Just go to View > Proof Setup > Monitor RGB. Then, you can use Ctrl Y to toggle between profiled and unprofiled colour.
Why might you do this?
Well, it’s another way to check for shape and detail in the most vivid areas of colour. It’s also a way to see blues as blue.
Despite how "good" it might look, none of the colours you’re looking at can be trusted. You’ve thrown all colour-management out the window, and if you happen to get a print that looks like that, it’s pure blind luck.
Some people consider this method as a valid way of checking how their images will look on the internet. Nope, sorry. All it tells you is how your images will look on the internet on your computer. It’s only a very vague guide about other people’s viewing experiences on their monitors, let alone their phones.
Flawed workaround #4
Remember Workaround #1, where we used a Hue/Saturation layer to check for detail? Well, we can sort of use the same methods for our purple blues.
First, you need to get some prints made, with some blues in them. Compare the prints to the digital images – the blues in the prints are probably much nicer than that annoying purple on screen.
Make a Hue/Saturation adjustment layer, and select "Blues". Then move the Hue slider to the left, to try to mimic the blues in the prints. (You may also need to adjust the Lightness slider.)
If you find a satisfactory result, you can make a note of the settings so you can use this "Blue Proof Layer" on every photo.
You’ll never get it exact. In fact, you might go insane trying. It’s just not possible. But it might get you a bit closer.
This is simply a form of soft-proofing. You can keep the layer active while you’re editing your image, but for heaven’s sake turn it off before output!!! Otherwise you’ll find your blues have all turned cyan in your prints.
Don’t let it get you down. Overall this is not a problem that will haunt you every minute you sit at your computer.
I encourage you to save your pennies for a better monitor in the future, but until you can afford it, don’t do anything rash.
Awareness is your best ally here. As long as you’re conscious of the situation, you can make informed decisions about your colours when editing, and safely minimise any printing problems.
If in doubt, print a little 6×4" proof before committing to a big expensive print for your wall.
And please don’t give up on monitor calibration – sure, it’s not perfect, but it’s much better than not calibrating.
If you have a question about this article, please feel free to post it in Ask Damien.