Colour management for book production

I’ve been busy working on the image selection / sequencing and text for my forthcoming book. I’m really pleased with how it is all going. But I am now at a stage where I want to print all of the 100+ images.

I don’t trust monitors for image review.

IMG_1436.jpg

As much as I am very confident that my monitor has been calibrated correctly, and profiled well, I still find that when I print, I’m forced to see things in the print that weren’t so obvious on the monitor. For one, luminance levels of a print can easily be misread on a monitor because our eye is highly adaptable. What may appear bright after staring at it for so long may appear much darker in print. So printing the images out allows me to get a real-world grasp on how the luminance levels are on the print.

That’s one reason to print. But there are many reasons to print and those reasons only become apparent once you have a print in your hands to review. So many times I’ve noticed colour casts, fine detail distractions that weren’t so obvious on the monitor, but once printed, I now notice them - both in the print and more interestingly, on the monitor as well.

Our eyes are highly adaptable, which leads us into tuning out colour casts ‘in our head’. So I’m always looking for a way to force my eye to see things that it has become blind towards. The more you stare at a picture on the screen, the more desensitised you become to it. It’s like tunnel vision of a sort.

So I definitely wish to print out all of the images that have been selected for inclusion in the book. But I want to go one stage further: I’d like to simulate how the images will look when printed on standard proofing paper:

“Standard Proofing Paper has a Fogra 39 certification, which is becoming the European standard. Offering the widest colour gamut available for accurate colour reproductions, this paper provides a base colour, weight and gloss level designed to match colour-critical commercial offset, press applications. Optimised for proofing applications, when used with our Epson UltraChrome K3 Ink with Vivid magenta, this media delivers outstanding short-term stability”

So this week I’ve been printing off some targets to get measured, so that I can have a custom profile built for this paper.

I’ve always printed my images out to verify them, and to give as a hard-copy to the printer. I was advised years ago that having a hard-copy is the ultimate reference when getting someone else to reproduce your work. I’ve been pretty happy with the colour reproduction on the last two books. But this next book will be a test of sorts, because we are working with some extreme edge blacks and off-colour whites.

I think that my optimising of the prints will go a lot smoother, and will be much finer if I am printing them on a standard kind of proofing paper that is close to an off-set press.

I realise this is perhaps of little use to many of you, but I suppose the big message here is - your photographs are never finished until you have them printed and verified. I always find errors and inconsistencies in my work once it’s printed, and if I tune the print to look good, then I know it will also look good on the monitor also. But not the other way around.

Printing's role as the final stage in image verification

Back in the days when I didn’t print, and asked a pro lab to do it for me, I always had a nagging feeling that I’d lost control of my baby.

I’m a self-confessed control freak when it comes to what I do. A few days ago I wrote a blog post about appetite because I think I know appetite well: whatever I get into, I never seem to get into it in half measures.

Screenshot+2019-03-17+at+09.53.56.jpg

Knowing this about me, you may be surprised to find out that at the beginning of my photographic journey, I often got my images printed by a lab. Indeed, I only started printing about 10 years ago.

For a long time I shied away from tackling what seemed like a formidable mountain because colour management was like a black art to me.

So I stayed away.

I’ve been extremely fortunate to have this blog. It has allowed me to meet people who have helped me and I put out a request about a decade ago for some help and suggestions about printing. Not one person left an entry on the blog, but instead chose to email me privately about it. The emails usually had this format to them:

“I don’t want to get flamed for my opinion, but this is how I do printing”.

It seemed that printing was a religion and to say you had a different way of doing it to someone else’s way was often contentious. A point of view is just that, and yet I am often surprised that we feel threatened when someone has a different view from ourselves.

Well, I welcomed the input but the message I got from the replies was this: everyone has their own way of working.

I doubt things have changed much in that regard over the past decade. There is still a lot of ways you can slice an onion, and there is always going to be a huge amount of fact vs personal preference.

So it’s now a decade further on, and I feel I know a thing or two about printing now. Indeed, I feel that everyone who loves photography should print. For one very simple reason: to validate your edits.

Even with a well calibrated and profiled computer monitor, I have learned that I cannot 100% trust it. I think it has something to do with how the eye interprets transmitted light compared to reflected light.

The fact is: I often notice areas that need further work when I study a printed version of an image. Stranger still, I often find that once I notice the error on the print, I can now see it on the monitor also. But the opposite is not true.

So printing is your last verification stage, and to paraphrase the wonderful Charlie Cramer :

“images that look good on a computer monitor aren’t guaranteed to look good in print,
but good prints are guaranteed to look good on a computer monitor”

Well, the issue for most who don’t print is: how to get started? It seems like such a black art. Yes, it is difficult to get started. There is so much contradictory advice out there. There is no one single way to do this correctly (even if I think my process is good).

I think this is why I’ve chosen to attempt to write an ebook about it. If I can reduce the information down to what you need, rather than getting too lost in the technology, then maybe I might be able to help you get a head start with this. I’ll see how it goes, but so far I’m feeling good about how much I’ve written. I think it’s coming together really well.

Colour compression & colour spaces

I’ve been working on some notes about printing lately. So this post today is all about colourspaces and what happens when we move an image from one colour space to another.

In the article I point out that colour management is not about colour accuracy, but more about how we choose to work around physical limitations as we move from one device to another, each with different colour gamuts.

2200 Matt paper has a small colour gamut, than Pro Photo RGB. So what can we do to make our image look good on 2200 Matt Paper even though it is physically impossible to do a direct conversion?

2200 Matt paper has a small colour gamut, than Pro Photo RGB. So what can we do to make our image look good on 2200 Matt Paper even though it is physically impossible to do a direct conversion?

The problem

Each device has its own physical limits to the range of colours it can record or reproduce. This is the problem: what do we do as we move an image from one device to another?

For example, when sending a file with a wide gamut of colours to a monitor or printer with a smaller gamut of colours, something has to be done with the colours that fall outside the physical range of the device’s effective gamut. Do we ignore those colours, or should we do something else with them?

The solution : Rendering Intent

The answer is : we decide, and we tell the colour management system our decision by way of a feature called Rendering Intent. Rendering Intent is where we tell the colour management system which rules to apply with respect to out of gamut colours.

There are several different rendering intents available. The two most commonly used rendering intents are Perceptual and Relative Colourmetric, which kind of do this:

Perceptual : shrink all the colours from the larger colourspace to fit the destination colourspace.

Relative Colourmetric : out of gamut colours are clipped, moved to their nearest relative within the new colourspace. All the other colours remain unchanged.

That’s a brief summary. Let’s consider them in more detail:

Perceptual

This rendering intent as the name suggests tries to adjust the content of the image so you perceive it as similar to the original image even though the colourspace is smaller. It does this by adjusting all the colours while keeping their relationship to each other intact. Although it is not ‘colour accurate’, most photographs look about right when it’s chosen as more often than not, it’s the relationships between the colours in the picture rather than their colour accuracy that is important. Here is an illustration to show how all the colours are shifted to fit the new colourspace:

Rendering-Intent-Perceptual.jpg

The other most common way of working around out of gamut colours is to choose relative colourmetric:

Relative Colourmetric

This rendering intent keeps all the colours that were within gamut unchanged. It’s a useful rendering intent when you want to ensure colour accuracy for certain colours - perhaps skin tones for example. Only the colours outside the gamut are clipped. They are moved to their nearest available in-gamut colour relative. As you can see below:

Rendering-Intent-Relative-Colourmetric.jpg

As you may now realise, colour reproduction is a compromise. And colours often have to get compressed if we are moving from a device with a wide gamut to a device with a smaller gamut.

We have to make the decision about which rendering intent to use. And the best way to choose the right one, is to demo them. If you are printing, then under the proofing preview, you can move between the different rendering intents to see how the colours are changed. Choose the rendering intent that suits your image the best.

No right or wrong way

Rendering Intent is best auditioned on a per image basis. Further, although an image may suit one rendering intent when printed on paper X, you may find that the same image prefers another rendering intent when printed on paper Y.

So you need to experiment on a per image basis.

But what about monitors? Do we have to compromise with them also?

As it happens, yes. Standard monitors have their own colour spaces (profiles), and when viewing something that comes from a larger colourspace on the monitor, a compromise has to be made.

Monitor Profile Rendering Intent

From what I understand, Monitor profiles are matrix based and this means that they have no idea how to deal with out of gamut colours. So they are simply clipped. In other words, when displaying out of gamut colours on a monitor, the monitor is essentially using a rendering intent of ‘Relative colourmetric’ (as illustrated above). We don’t have a choice about rendering intent when displaying an image on a monitor. It’s always ‘relative-colourmetric’.

In the diagram below, I have a Pro Photo colourspace image open in Photoshop, but I am viewing it on a monitor that has a smaller colourspace than Pro Photo. The colour management system responsible for the conversion from the image profile simply displays the colours unchanged, and any colour that it can’t display is just clipped to its nearest relative within the monitor colourspace.

monitor-profile-rendering-intent.jpg

In summary

  • Colour management is not the same thing as colour accuracy.

  • To manage colours, we need to have profiles that describe the colour gamut of each device, but we also have to make decisions on how to deal with colours that fall outside the gamut of a particular device. This is called the rendering intent.

  • We can choose which rendering intent to use when printing.

  • But we have no control over how out-of-gamut colours are displayed on computer monitors, they are just clipped to fit the nearest colour within the destination colour space.

A few thoughts on writing e-Books

Over the years, I’ve been writing e-books with the aim that they become more ‘reference’ material than something attributable to magazine content.

When I put ‘Simplifying Composition’ together, it took me about a year to really think it through, to figure out what I needed to say and to then formulate it on paper. It’s not the writing that takes the time, it’s the idea, the concept, and the arrangement of the words so that the message is as clear as it can be.

And that was the hardest part of all - figuring out what it is that I needed to convey in writing. The message needed to be simple. It needed to be clear, and for that to happen, I needed to be clear myself with what I wanted to say.

It is often in the process of explaining something that I find holes in my own knowledge. If I’m finding it hard to explain something it’s usually because I don’t fully understand something as much as I thought I did. Writing an e-book is a self-learner, a process of self-help. Of clarifying my own ideas and filling in the gaps in my own knowledge.

Fast Track to Photoshop
11.99
Add To Cart

Writing an e-book about Photoshop was similar. It took about 2 years for me to do this one. I think the first year was mostly procrastination, brought on by a feeling of difficulty. You see, Photoshop’s tool set is huge. And the truth of the matter is that photographers only need about 10% of the program.

It took me a while to realise that most Photoshop book are like reference manuals. They may be in-depth and tell you everything about the program, but they suck at getting you off the ground, of cutting out the chaff, and of getting you to the tools that you really need to know.

So it took me a while to figure out that photographers just need to learn Layers, Masks and Curves to get going. Write an eBook about those features and you’ve given everyone a head-start, a push in the right direction, rather than getting lost in some massive reference manual with no idea where they are going.

How does one write a book about printing?

And this is the problem I’m at right now.

The subject of printing is massive. It has to cover monitor calibration, monitor profiling, profiles, proofing, colour spaces. Each of those is a massive topic on its own, so I have come to realise that I need to have a ‘fast track’ way of cutting out the noise, of cutting through all the technology to get people up to speed as quickly as possible.

But there is so much miss-information and miss-understanding out there.

fast-track-printing.png

Many think they need to profile their printer, many think that their camera works in Adobe RGB colour space.

Many think that all devices work in Adobe RGB colour space when in fact they don’t. They work in their own proprietary colour space and the colours they’re capable of recording or reproducing may not fit exactly any particular colour space - they have their own personal signature.

Similarly, so many people think that their printers work in RGB, they don’t. They are CMYK devices. Just go and look at the ink sets used on any Epson Ultrachrome ink printer - there’s a clue in the names - Light Cyan, Light Magenta, Yellow…. . So although there are beliefs out there that CMYK is a smaller colourspace than Adobe RGB, it’s not true - they’re just different,.

Lastly, understanding printing is about understanding that everything is a compromise.

So too, is writing an e-book about it.

In the works

During last year’s printing workshop, I found that we got stuck in too much detail about the technology. Monitor calibration for instance, is a big topic that can consume you for days. Colour spaces were often confusing for most, and then there was the issue of rendering intent. Why do you have to choose the rendering intent in the print driver, even though it’s been set in the proofing set up? Some folks got confused between proofing settings and printing settings and couldn’t understand why they are different, and have different purposes.

Then there was the aspect of sharpening, and paper profiles. Yet another large topic that one can get lost in for days, if not years.

But it had to be covered. You need to know this stuff if you want to get good at printing.

Screenshot 2019-02-03 at 19.52.33.png

I’ve got to prepare some notes for this years workshop. So participatns have something to refer to when they get lost. Rather than getting stuck going over the same material, I need to crystallise the information so I can keep the workshop on track, and those that find some parts confusing have notes to refer to.

So that’s what I’m doing. I’ve been working on the content of this workshop for the past few months and I’ve pretty much come to the conclusion that it would suit an e-book as well.

It’s a massive topic. And I felt a sense of dissatisfaction from some workshop participants - how do you learn about printing in a week? You can’t. It’s like trying to learn about composition in a week. You can’t. All you can do is point people in the right direction and try to cut out some of the crap. Cut down the chances of them going down the wrong avenues and getting lost down them for years.

So I think there is room for a stripped down information pack that cuts through a lot of the information out there, and tries to simplify it down to what you just need to know to get up and running. So that’s what I hope to do with this new e-book that is currently in development.

Stay tuned.

1 Space available for Printing Masterclass

I have had a cancellation for next May’s printing Masterclass. Perhaps this is of interest to you?

Fine Art Printing Photoshop-CS Masterclass
448.00

Image Interpretation & Printing Techniques


2019, May 27 - 01



Price: £1,695
Deposit: £448


6-Day Photographic Mentoring Workshop
Wester Ross, Scottish Highlands

 

Introduction

This workshop will cover the technical workflow aspects of printing from Screen calibration, proofing to print evaluation.

As part of printing your work, we will cover the same lessons taught in my Digital Darkroom' workshop, because good prints are made from good edits. And good edits can only be verified by printing.

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Winter Sunrise from Lone Pine - Ansel Adams

As part of my Digital Darkroom and Printing workshops, I enjoy enormously showing the beautiful Ansel Adams photograph 'winter sunrise from lone pine'  to my class. It's a great illustration of the 'creative edit' and well worth discussing in detail. 

'Winter sunrise from lone pine', the achingly beautiful image with wondrous print interpretation by Ansel Adams
Image © Ansel Adams

Before I dissect the image, I am curious if you can actually see the edits that Ansel has done to the image? Are they very apparent to you? I only ask for the sake of wondering how much skill each of us possess at deconstructing an image, or whether each of us simply just 'buy it' when we look at the photograph? My own thoughts on this are that great images tend to cast a spell on us and we are too enwrapped in enjoying the spell we're under to think more about how the image is constructed. As part of our 'learning to become better photographers', I think it is natural to be able to 'enjoy an image' as well as dissect it.

I think great photographs cast a spell on us with their imagery, and whether they are 'real' or not is irrelevant. 

Ansel Adams was a great illusionist. When I look at his images I believe them, even though I know a lot of work went into the manipulation of the negative in the dark room. To me - this  is what photography is all about..

Let's break down Ansel's image into it's core parts:

lone-pine-dissection.jpg

Ansel's image can be broken down into four summary edits (I'm sure there were more, but these are the ones I see he has attempted), which I've illustrated above in different colours:

Image Analysis

Blue area:
The Sky. Which seems to have been printed with as little contrast as possible to try to reduce the brilliance / emphasis of the cloud at the far right of the picture. If the clouds had more contrast then they would be competing with the white mountain for attention, and ultimately, stealing a little bit of the mountain's main attention grabbing ability.

Orange area:
The snowy mountains and dark hill. This is the high-contrast area of the scene and the area that is the 'initial pull'. Although this area takes us into the picture, it is not the last thing our eye settles on.

Green area:
Ground area, a necessary part of the picture, because it gives us context, even though it adds little interest to the image.

Red area:
Forest & horse. The part of the image I consider the 'easter egg' - that special bit of surprise that you see after you've looked at the high contrast mountains.
 

 

Making the print

Let us now consider the image from how Ansel may have chosen to print / edit it. If I were to make a guess on what choices Ansel made, I would assume the following:

Blue area

He would have reduced the contrast here as much as he possibly could. His aim would have been to suppress that white cloud on the far right hand side of the image, so that it does not compete with the brilliance of the jagged mountain range. He wants the white mountain to be as bright as possible, and the only way to do that is to suppress bright tones elsewhere in the image. The key is - if you want something to be brighter, darken everything else around it. So I believe that Ansel has darkened the sky for two reasons: it makes the mountain appear brighter, and it also reduces the distraction of the cloud.

Orange area

This is the main part of the image: what we are really coming to look at. It is perhaps the most 'closest to reality part of the image',. The white snowy mountain had a lot of directional hard light on it and the shadows are sharply defined here. If the image had been made on a soft-light day, even by adding a lot of contrast the shadows would have still been very diffused. So I think it's fair to say it was a high-contrast day, and Ansel has let the mountains be what it is: a high contrast subject.

With regards to the dark curvy hill, my guess is that it is impossible to put in a sudden separation in tone if there was none in the negative. So I would assume that the hill was dark, or underexposed, but by burning further in, Ansel has allowed the dark nature of the hill to become more prominent.

Green area

The contrasts in this part of the frame need to be kept under control so that the eye goes straight to the mountains and secondly to the horse. So Ansel has had to finely balance the ground so that it's not too dark or or light: not too dominant in either way: it needs to be wallpaper to a degree so the eye can scan over it and not get stuck in there.

Red Area

This is the 'easter egg' of the picture. It's the 'surprise element' that you only see after you have been drawn to the mountains upon first viewing. 

For this part of the print, Ansel has chosen to dodge the surrounding area around the horse, to give the illusion that the sun is highlighting the are where the horse is. To do this he has deliberately avoided exposing the paper at this region to lighten up the forest, but he has also had to make sure that the horse stays very dark even though he is dodging. I think he would have altered contrasts here to accomplish that.

 

In summary

This image is really about two subjects. The primary one is the mountain range of extreme highlights and dark tones contrasting with each other. The secondary subject is the horse. It's what you see after you eye has moved away from the mountain range.

To accomplish this, Ansel has darkened down a good proportion of the image and left two subjects to be as bright as naturally possible: the white mountains and the area around the horse. He has masterfully orchestrated our eye to initially be attracted to the brightness and contrasts of the white mountain and dark hill, and then to move straight to the horse in the lower part of the frame. Everything else has either been darkened or had contrast removed so the viewers eye does not get pulled away from the main areas of interest in the picture.

It is a masterpiece of editing skill and it always amazes me when I look at it.

Editing is indeed a skill. It is a life-long endeavour to search for the underlying meaning in our work and to bring it out. Sometimes to emphasise certain areas of the picture, we need to reduce surrounding areas by a large degree to let the areas we are interested in stand out. This image is a great example of that.

 

 

 

You need to print to Verify your edits

I'm just home from my first printing workshop. We had a great time and as much as workshops are there to teach my participants, I always learn a lot too. No one's learning is ever complete.

At the start of the week I explained to my group that although having a tightly calibrated / profiled monitor that matches what we see in print is something we strive for: it is not ideal. The truth is, that the only way to verify what we have in our files is to print. I am not alone in knowing that even with a highly profiled monitor I can be mislead. It is only the print that is honest: it shows me what is right and also what is wrong. Errors that I did not see on the monitor become evident in the print, and once I return to the monitor to check if they were there also, I see they were there all along.

The great American photographer Charlie Cramer has often said that 'computer monitors have their own reality distortion field. The more you look at them, the more your eye adapts. The only way to see what is really in your file is to print'.  I'd sure love to attend one of Charlie's workshops sometime. He is someone I have heard consistently great things about: he sounds like a great teacher.

The thing about profiling computer monitors is that you can't trust the software. It is always 'aiming for the target you set, but often finding out that it can't reach it'. So when your calibration software says 'your monitor is calibrated', what it is often saying is this; 'I did my best'. There are a few reasons for this: firstly, depending on the monitor hardware, it may have a difficult time trying to reach the white-point and luminance levels you are asking for. I know my old Eizo lost shadow detail when I tried to calibrate it down to 100 candles. It was too low for the monitor.

I use BasICColour's Display 5 software. Below it shows you how 'close' it got to what I was aiming for (known as the delta). You can see that my colorimeter and software got very very close indeed. But this still only means that the software got close to what I aimed for. But you may be aiming for the wrong result......

BasICColour Display Calibration & Profiling software shows you just how much of a delta there was between what you aimed for, and what you got when you calibrated / profiled. You can see I chose a luminance of 100cdm, and the black point of the monitor can't reach absolute zero, so I've set it to what it's physically capable of reaching (0.26cdm). Even with this report showing me the delta, I still need a verification test proof to compare with my monitor: the only way to confirm your profiling is visually.

BasICColour Display Calibration & Profiling software shows you just how much of a delta there was between what you aimed for, and what you got when you calibrated / profiled. You can see I chose a luminance of 100cdm, and the black point of the monitor can't reach absolute zero, so I've set it to what it's physically capable of reaching (0.26cdm). Even with this report showing me the delta, I still need a verification test proof to compare with my monitor: the only way to confirm your profiling is visually.

You need to have something to verify against. Just because your software says 'I did it!', means nothing. If you are finding that your prints look warmer than your monitor, then you are probably using the wrong white-point setting. To find out what that should be, requires you compare your calibration with a day-light viewing booth. On the image below I have a daylight viewing booth (colour temperature is D50 - 5000K) and to match that, my computer monitor is around 5,800K. Each monitor will vary. Some may be higher in colour temperature while others may be lower. Just because I asked my calibration software to reach D65 (6,500K) means it is only a target it is aiming for. In truth, D65 on a monitor is far to cool.

You can't trust the numbers, only the visual inspection. That means iterating around the profiling / calibration software looking for a white-point that matches a viewing target. Once you find that colour temperature for your monitor, you now have a place to evaluate your prints.

Even though my monitor is tightly profiled and calibrated to match my GTI viewing booth, I still see errors in the final print that were actually present in the monitor representation. I now feel I still have to learn to 'interpret' what my monitor is telling me, and not to trust it too much.

Even though my monitor is tightly profiled and calibrated to match my GTI viewing booth, I still see errors in the final print that were actually present in the monitor representation. I now feel I still have to learn to 'interpret' what my monitor is telling me, and not to trust it too much.

Once I have my monitor showing a close representation of what is under my viewing booth may I evaluate my prints. And this is where the fun begins: this is when you will find tonal distractions, colour casts and other distractions in the final print that you 'thought' weren't on your monitor. Looking back at your monitor to review, you will find they were there all along. 

The human eye is highly adaptable. One thing I have learned is that my visual system is constantly trying to lie to me. Monitors only get me so far. I have to print to verify what I think is in the file. Even if the calibration and profiling of my monitor closely represents what is on print.

I'd go one step further by adding in what Charlie Cramer has to say about the printing process:

"Poor images can look great on a monitor but will always look bad in print. Whereas great prints always look great on a computer monitor"

Your images aren't complete until you've printed them, and then further optimised them.

You have to print.

Good Printing means good Editing

Four years ago when I first introduced my Digital Darkroom workshop, it was the least popular thing I offered in my list of workshops. I was personally surprised by this, as I had thought that this kind of workshop would be something a lot of people would be looking for. I was wrong.

It has taken this number of years to establish the course, and now it fills up very quickly each year. I'm glad that photographers have come to realise that editing is a skill that requires as much thought and deliberation as our fieldwork.

"Good edits come from improved visual awareness"

 

Editing isn't about just making the image a little more punchy, neither is it about applying templates to your work to make them look better, and it certainly isn't about trying to fix a bad image. Editing is about working with the tones within the picture, so you can navigate the viewer's eye around the aspects you want them to look at, and to take their eye away from the areas you wish to place in the background.

fine-art-printing.jpg

Right now, we are living in a period where the emphasis is on shooting. Editing is almost an afterthought. Something that is done afterwards. For some it is an attempt to 'try to make the picture look good', and for the few who have figured it out - they have come to realise that editing is related to what they noticed in the field. Indeed, I often choose locations to make a picture due to their tonal properties - I know they will work well in the edit stage because they have enough tonal separation to work with.

I do not treat the editing stage lightly. I have found it is perhaps the biggest contributor to my 'style'. It is a highly creative space to work in and I will spend hours, if not days and weeks working on a portfolio of new images.

I'd also add;

"Good prints are made from good edits.
And good edits can only be verified by reviewing prints"

 

This is most certainly true. You can't make a good print from a badly edited image, and likewise, you can't make a good edit without printing it to evaluate it. Let me explain.

When I came to preparing my Colourchrome book for publication last year, I printed every single one of the 40 images. I had to do this because it's the only way to confirm to myself that I've got my edits right.
 

"A calibrated and profiled monitor will only get you so far.
I've been fooled many times by seeing colour casts and other problems in the final print that weren't initially obvious on the monitor.
I would go back to see if they were visible on the monitor only to find out they were. I now print to verify that what I'm seeing is true. It's the only way"

 

Even though my monitor is calibrated and profiled to give me the most accurate representation of what's in my files, I still find discrepancies once I print them. This is because the eye is highly adaptable and once we've seen the image on the monitor for a while, we adapt to the monitor's colour and tonal response. For me, I've found that after a while I can't see colour casts. I need to print the work to verify it.

When I find discrepancies in the print, I go back to the monitor to check if those discrepancies are visible there also. They always are. Yet I had not seen them, because my eye had 'adapted' to the monitor the more I looked at it and I've come to realise that there is yet another skill required to 'interpret' what my monitor shows me.

Until I master being able to 'read' my monitor, the only way to 'see' the picture, is to print it out.
 

"We all should print.
It forces us to look again"

 

Prints also force us to take note of the luminosity of the tones in the print. It's only when I print that I notice that I'm not taking advantage of the tonal range available to me. You can of course use the hand widget in the Curves tool to interrogate tones to find out where they reside in the tonal scale. Or even use the LAB mode's Luminosity value in the info palette to show you where the tones really reside, but you still need to print the image out.
 

"Where I once thought something was bright and stood out,
I
'm sometimes confronted with a lacklustre tonal range in print.
The print tells me I haven't gone far enough"

 

It's really a case of learning to interpret what your monitor is telling you. It's very hard to do because our eye adapts to what the monitor shows us and we become blind to what is actually there. 
 

"If you aren't printing: then you aren't getting the most out of your edits.
And ultimately, the images aren't optimised"

 

So you need to print. All photographers should print because it is a vital step in pushing your images to the best they can be.

Printing is also a step in learning to 'see' better, because we are forced to look again, to re-interpret the print and notice how it differs from what we thought you were seeing on our monitor.

My advice is - print, and incorporate it as part of your editing workflow. Printing helps inform your edits and show where you need to tighten up on tones that aren't as bold as you thought they were.

"Did I say you need to print? 
...You need to print!"