Monitor Calibration Update

Posted on April 2, 2017 by Andrew Astbury

Monitor Calibration Update

Okay, so I no longer NEED a new monitor, because I’ve got one – and my wallet is in Leighton Hospital Intensive Care Unit on the critical list..

What have you gone for Andy? Well if you remember, in my last post I was undecided between 24″ and 27″, Eizo or BenQ. But I was favoring the Eizo CS2420, on the grounds of cost, both in terms of monitor and calibration tool options.

But I got offered a sweet deal on a factory-fresh Eizo CS270 by John Willis at Calumet – so I got my desire for more screen real-estate fulfilled, while keeping the costs down by not having to buy a new calibrator.

But it still hurt to pay for it!

Monitor Calibration

There are a few things to consider when it comes to monitor calibration, and they are mainly due to the physical attributes of the monitor itself.

In my previous post I did mention one of them – the most important one – the back light type.

CCFL and WCCFL – cold cathode fluorescent lamps, or LED.

CCFL & WCCFL (wide CCFL) used to be the common type of back light, but they are now less common, being replaced by LED for added colour reproduction, improved signal response time and reduced power consumption. Wide CCFL gave a noticeably greater colour reproduction range and slightly warmer colour temperature than CCFL – and my old monitor was fitted with WCCFL back lighting, hence I used to be able to do my monitor calibration to near 98% of AdobeRGB.

CCFL back lights have one major property – that of being ‘cool’ in colour, and LEDs commonly exhibit a slightly ‘warmer’ colour temperature.

But there’s LEDs – and there’s LEDs, and some are cooler than others, some are of fixed output and others are of a variable output.

The colour temperature of the backlighting gives the monitor a ‘native white point’.

The ‘brightness’ of the backlight is really the only true variable on a standard type of LCD display, and the inter-relationship between backlight brightness and colour temperature, and the size of the monitors CLUT (colour look-up table) can have a massive effect on the total number of colours that the monitor can display.

Industry-standard documentation by folk a lot cleverer than me has for years recommended the same calibration target settings as I have alluded to in previous blog posts:

White Point: D65 or 6500K

Brightness: 120 cdm² or candelas per square meter

Gamma: 2.2

The ubiquitous ColorMunki Photo ‘standard monitor calibration’ method setup screen.

This setup for ‘standard monitor calibration’ works extremely well, and has stood me in good stead for more years than I care to add up.

As I mentioned in my previous post, standard monitor calibration refers to a standard method of calibration, which can be thought of as ‘software calibration’, and I have done many print workshops where I have used this method to calibrate Eizo ColorEdge and NEC Spectraviews with great effect.

However, these more specialised colour management monitors have the added bonus of giving you a ‘hardware monitor calbration’ option.

To carry out a hardware monitor calibration on my new CS270 ColorEdge – or indeed any ColorEdge – we need to employ the Eizo ColorNavigator.

The start screen for ColorNavigator shows us some interesting items:

The recommended brightness value is 100 cdm² – not 120.

The recommended white point is D55 not D65.

Thank God the gamma value is the same!

Once the monitor calibration profile has been done we get a result screen of the physical profile:

Now before anyone gets their knickers in a knot over the brightness value discrepancy there’s a couple of things to bare in mind:

This value is always slightly arbitrary and very much dependent on working/viewing conditions. The working environment should be somewhere between 32 and 64 lux or cdm² ambient – think Bat Cave! The ratio of ambient to monitor output should always remain at between 32:75/80 and 64:120/140 (ish) – in other words between 1:2 and 1:3 – see earlier post here.
The difference between 100 and 120 cdm² is less than 1/4 stop in camera Ev terms – so not a lot.

What struck me as odd though was the white point setting of D55 or 5500K – that’s 1000K warmer than I’m used to. (yes- warmer – don’t let that temp slider in Lightroom cloud your thinking!).

After all, 1000k is a noticeable variation – unlike the brightness 20cdm² shift.

Here’s the funny thing though; if I ‘software calibrate’ the CS270 using the ColorMunki software with the spectro plugged into the Mac instead of the monitor, I visually get the same result using D65/120cdm² as I do ‘hardware calibrating’ at D55 and 100cdm².

The same that is, until I look at the colour spaces of the two generated ICC profiles:

The coloured section is the ‘software calibration’ colour space, and the wire frame the ‘hardware calibrated’ Eizo custom space – click the image to view larger in a separate window.

The hardware calibration profile is somewhat larger and has a slightly better black point performance – this will allow the viewer to SEE just that little bit more tonality in the deepest of shadows, and those perennially awkward colours that sit in the Blue, Cyan, Green region.

It’s therefore quite obvious that monitor calibration via the hardware/ColorNavigator method on Eizo monitors does buy you that extra bit of visual acuity, so if you own an Eizo ColorEdge then it is the way to go for sure.

Having said that, the differences are small-ish so it’s not really worth getting terrifically evangelical over it.

But if you have the monitor then you should have the calibrator, and if said calibrator is ‘on the list’ of those supported by ColorNavigator then it’s a bit of a JDI – just do it.

You can find the list of supported calibrators here.

Eizo and their ColorNavigator are basically making a very effective ‘mash up’ of the two ISO standards 3664 and 12646 which call for D65 and D50 white points respectively.

Why did I go CHEAP ?

Well, cheaper…..

Apart from the fact that I don’t like spending money – the stuff is so bloody hard to come by – I didn’t want the top end Eizo in either 27″ or 24″.

With the ‘top end’ ColorEdge monitors you are paying for some things that I at least, have little or no use for:

3D CLUT – I’m a general sort of image maker who gets a bit ‘creative’ with my processing and printing. If I was into graphics and accurate repro of Pantone and the like, or I specialised in archival work for the V & A say, then super-accurate colour reproduction would be critical. The advantage of the 3D CLUT is that it allows a greater variety of SUBTLY different tones and hues to be SEEN and therefore it’s easier to VISUALLY check that they are maintained when shifting an image from one colour space to another – eg softproofing for print. I’m a wildlife and landscape photographer – I don’t NEED that facility because I don’t work in a world that requires a stringent 100% colour accuracy.
Built-in Calibrator – I don’t need one ‘cos I’ve already got one!
Built-in Self-Correction Sensor – I don’t need one of those either!

So if your photography work is like mine, then it’s worth hunting out a ‘zero hours’ CS270 if you fancy the extra screen real-estate, and you want to spend less than if buying its replacement – the CS2730. You won’t notice the extra 5 milliseconds slower response time, and the new CS2730 eats more power – but you do get a built-in carrying handle!

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Gamma Encoding – Under the Hood

Posted on January 29, 2014 by Andrew Astbury

Gamma, Gamma Encoding & Decoding

Gamma – now there’s a term I see cause so much confusion and misunderstanding.

So many people use the term without knowing what it means.

Others get gamma mixed up with contrast, which is the worst mistake anyone could ever make!

Contrast controls the spatial relationship between black and white; in other words the number of grey tones. Higher contrast spreads black into the darker mid tones and white into the upper mid tones. In other words, both the black point and white point are moved.

The only tones that are not effected by changes in image gamma are the black point and white point – that’s why getting gamma mixed up with contrast is the mark of a “complete idiot” who should be taken outside and summarily shot before they have chance to propagate this shocking level of misunderstanding!

What is Gamma?

Any device that records an image does so with a gamma value.

Any device which displays/reproduces said image does so with a gamma value.

We can think of gamma as the proportional distribution of tones recorded by, or displayed on, a particular device.

Because different devices have different gamma values problems would arise were we to display an image that has a gamma of X on a display with a gamma of Y:

Ever wondered what a RAW file would look like displayed on a monitor without any fancy colour & gamma managed software such as LR or ACR?

A raw file displayed on the back of the camera (left) and as it would look on a computer monitor calibrated to a gamma of 2.2 & without any colour & gamma management (right).

The right hand image looks so dark because it has a native gamma of 1.0 but is being displayed on a monitor with a native gamma of 2.2

RAW file Gamma

To all intents and purposes ALL RAW files have a gamma of 1.0

Camera Sensor/Linear Gamma (Gamma 1.0)

Digital camera sensors work in a linear fashion:

If we have “X” number of photons striking a sensor photosite then “Y” amount of electrons will be generated.

Double the number of photons by doubling the amount of light, then 2x “Y” electrons will be generated.

Halve the number of photons by reducing the light on the scene by 50% then 0.5x “Y” electrons will be generated.

We have two axes on the graph; the horizontal x axis represents the actual light values in the scene, and the vertical y axis represents the output or recorded tones in the image.

So, if we apply Lab L* values to our graph axes above, then 0 equates to black and 1.0 equates to white.

The “slope” of the graph is a straight line giving us an equal relationship between values for input and output.

It’s this relationship between input and output values in digital imaging that helps define GAMMA.

In our particular case here, we have a linear relationship between input and output values and so we have LINEAR GAMMA, otherwise known as gamma 1.0.

Now let’s look at a black to white graduation in gamma 1.0 in comparison to one in what’s called an encoding gamma:

Linear (top) vs Encoded Gamma

The upper gradient is basically the way our digital cameras see and record a scene.

There is an awful lot of information about highlights and yet the darker tones and ‘shadow’ areas are seemingly squashed up together on the left side of the gradient.

Human vision does not see things in the same way that a camera sensor does; we do not see linearly.

If the amount of ambient light falling on a scene suddenly doubles we will perceive the increase as an unquantifiable “it’s got brighter”; whereas our sensors response will be exactly double and very quantifiable.

Our eyes see a far more ‘perceptually even’ tonal distribution with much greater tonal separation in the darker tones and a more compressed distribution of highlights.

In other words we see a tonal distribution more like that contained in the gamma encoded gradient.

Gamma encoding can be best illustrated with another graph:

Linear Gamma vs Gamma Encoding 1/2.2 (0.4545)

Now sadly this is where things often get misunderstood, and why you need to be careful about where you get information from.

The cyan curve is NOT gamma 2.2 – we’ll get to that shortly.

Think of the graph above as the curves panel in Lightroom, ACR or Photoshop – after all, that’s exactly what it is.

Think of our dark, low contrast linear gamma image as displayed on a monitor – what would we need to do to the linear slope to improve contrast and generally brighten the image?

We’d bend the linear slope to something like the cyan curve.

The cyan curve is the encoding gamma 1/2.2.

There’s a direct numerical relationship between the two gamma curves; linear and 1/2.2. and it’s a simple power law:

V_O = V_I^γwhere V_O = output value, V_I = input value and γ = gamma

Any input value (V_I) on the linear gamma curve to the power of γ equals the output value of the cyan encoding curve; and γ as it works out equals 0.4545

V_I 0 = V_O 0
V_I 0.25 = V_O 0.532
V_I 0.50 = V_O 0.729
V_I 0.75 = V_O 0.878
V_I 1.0 = V_O 1.0

Now isn’t that bit of maths sexy………………..yeah!

Basically the gamma encoding process remaps all the tones in the image and redistributes them in a non-linear ratio which is more familiar to our eye.

Note: the gamma of human vision is not really gamma 1/2.2 – gamma 0.4545. It would be near impossible to actually quantify gamma for our eye due to the behavior of the iris etc, but to all intents and purposes modern photographic principles regard it as being ‘similar to’..

So the story so far equates to this:

Gamma encoding redistributes tones in a non-linear manner.

But things are never quite so straight forward are they…?

Firstly, if gamma < 1 (less than 1) the encoding curve goes upwards – as does the cyan curve in the graph above.

But if gamma > 1 (greater than 1) the curve goes downwards.

A calibrated monitor has (or should have) a calibrated device gamma of 2.2:

Linear, Encoding & Monitor gamma curves.

As you can now see, the monitor device gamma of 2.2 is the opposite of the encoding gamma – after all, the latter is the reciprocal of the former.

So what happens when we apply the decoding gamma/monitor gamma of 2.2 to our gamma encoded image?

The net effect of Encode & Decode gamma – Linear.

That’s right, we end up back where we started!

Now, are you thinking:

Don’t understand?
We are back with our super dark image again?

Welcome to the worlds biggest Bear-Trap!

The “Learning Gamma Bear Trap”

Hands up those who are thinking this is what happens:

If your arm so much as twitched then you are not alone!

I’ll admit to being naughty and leading you to edge of the pit containing the bear trap – but I didn’t push you!

While you’ve been reading this post have you noticed the occasional random bold and underlined text?

Them’s clues folks!

The super dark images – both seascape and the rope coil – are all “GAMMA 1.0 displayed on a GAMMA 2.2 device without any management”.

That doesn’t mean a gamma 1.0 RAW file actually LOOKS like that in it’s own gamma environment!

That’s the bear trap!

Gamma 1.0 to gamma 2.2 encoding and decoding

Our RAW file actually looks quite normal in its own gamma environment (2nd from left) – but look at the histogram and how all those darker mid tones and shadows are piled up to the left.

Gamma encoding to 1/2.2 (gamma 0.4545) redistributes and remaps those all the tones and lightens the image by pushing the curve up BUT leaves the black and white points where they are. No tones have been added or taken away, the operation just redistributes what’s already there. Check out the histogram.

Then the gamma decode operation takes place and we end up with the image on the right – looks perfect and ready for processing, but notice the histogram, we keep the encoding redistribution of tones.

So, are we back where we started? No.

Luckily for us gamma encoding and decoding is all fully automatic within a colour managed work flow and RAW handlers such as Lightroom, ACR and CapOnePro etc.

Image gamma changes are required when an image is moved from one RGB colour space to another:

ProPhoto RGB has a gamma of 1.8
Adobe RGB 1998 has a gamma of 2.2
sRGB has an oddball gamma that equates to an average of 2.2 but is nearly 1.8 in the deep shadow tones.
Lightrooms working colour space is ProPhoto linear, in other words gamma 1.0
Lightrooms viewing space is MelissaRGB which equates to Prophoto with an sRGB gamma.

Image gamma changes need to occur when images are sent to a desktop printer – the encode/decode characteristics are actually part and parcel of the printer profile information.

Gamma awareness should be exercised when it comes to monitors:

Most plug & play monitors are set to far too high a gamma ‘out the box’ – get it calibrated properly ASAP; it’s not just about colour accuracy.
Laptop screen gamma changes with viewing position – God they are awful!

Anyway, that just about wraps up this brief explanation of gamma; believe me it is brief and somewhat simplified – but hopefully you get the picture!

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Lightroom Tutorials #2

Posted on December 5, 2013 by Andrew Astbury

Lightroom Tutorials,video,lessoneagle,golden eagle,snow,winter,Norway,wildlife

Image Processing in Lightroom & Photoshop

In this Lightroom tutorial preview I take a close look at the newly evolved Clone/Heal tool and dust spot removal in Lightroom 5.

This newly improved tool is simple to use and highly effective – a vast improvement over the great tool that it was already in Lightroom 4.

Lightroom Tutorials Sample Video Link below: Video will open in a new window

https://vimeo.com/64399887

This 4 disc Lightroom Tutorials DVD set is available from my website at http://wildlifeinpixels.net/dvd.html

Colour Space & Profiles

Posted on November 30, 2013 by Andrew Astbury

From Camera to Print
copyright 2013 Andy Astbury/Wildlife in Pixels

Colour space and device profiles seem to cause a certain degree of confusion for a lot of people; and a feeling of dread, panic and total fear in others!

The reality of colour spaces and device profiles is that they are really simple things, and that how and why we use them in a colour managed work flow is perfectly logical and easy to understand.

Up to a point colour spaces and device profiles are one and the same thing – they define a certain “volume” of colours from red to green to blue, and from black to white – and all the colours that lie in between those five points.

The colour spaces that most photographers are by now familiar with are ProPhotoRGB, AdobeRGB(1998) and sRGB – these are classed as “working colour spaces” and are standards of colour set by the International Color Consortium, or ICC; and they all have one thing in common; where red, green and blue are present in equal amounts the colour produced will be NEUTRAL.

The only real differences between these three working colour spaces is the “distances” between the five set points of red, green, blue, black and white. The greater the distance between the three primary colours then the greater is the degree of graduation between them, hence the greater the number of potential colours. In the diagram below we can see the sRGB & ProPhoto working colour spaces displayed on the same axes:

The sRGB & ProPhoto colour spaces. The larger volume of ProPhoto contains more colour variety between red, green & blue than sRGB.

If we were to mark five different points on the surface of a partially inflated balloon, and then inflate it some more then the points in relation to the balloons surface would NOT change: the points remain the same. But the spatial distances between the points would change, as would the internal volume. It’s the same with our five points of colour reference – red, green, blue, black & white – they do NOT change between colour spaces; red is red no matter what the working colour space. But the range of potential colours between our 5 points of reference increases due to increased colour space volume.

So now we have dealt with the basics of the three main working colour spaces, we need to consider the volume of colour our camera sensor can capture – if you like, its colour space; but I’d rather use the word “gamut”.

Let’s take the Canon 5DMk3 as an example, and look at the volume, or gamut, of colour that its sensor can capture, in direct comparison with our 3 quantifiable working colour spaces:

The Canon 5DMk3 sensor gamut (black) in comparison to ProPhoto (largest), AdobeRGB1998 & sRGB (smallest) working colour spaces.

In a previous blog article I wrote – see here – I mentioned how to setup the colour settings in Photoshop, and this is why. If you want to keep the greatest proportion of your camera sensors captured colour then you need to contain the image within the ProPhotoRGB working colour space. If you don’t, and you use AdobeRGB or sRGB as Photoshops working colour space then you will loose a certain proportion of those captured colours – as I’ve heard it put before, it’s like a sex change operation – certain colours get chopped off, and once that’s happened you can’t get them back!

To keep things really simple just think of the 3 standard working colour spaces as buckets – the bigger the bucket, the more colour it contains; and you can’t tip the colours captured by your camera into a smaller bucket without getting spillage and making a mess on the floor!

As I said before, working colour spaces are neutral; but seldom does our camera ever capture a scene that contains pure neutrals. Even though an item in the scene may well be neutral in colour, camera sensors quite often skew these colours ever so slightly; most Canon RAW files always look a teeny-weeny ever so slight bit magenta to me when I import them; but there again I’m a Nikon shooter seem to have a minute greenish tinge to them before processing.

Throughout our imaging work flow we have 3 stages:

1. Input (camera or scanner).

2. Working Process (Lightroom, Photoshop etc).

3. Output (printer for example).

And each stage has its representative type of colour space – we have input profiles, working colour spaces and output profiles.

So we have our camera capture gamut (colour space if you like) and we’ve opened our image in Photoshop or Lightroom in the ProPhoto working colour space – there’s NO SPILLAGE!

We now come to the crux of colour management; before we can do anything else we need to profile our “window onto our image” – the monitor.

In order to see the reality of what the camera captured we need to ensure that our monitor is in line with our WORKING COLOUR SPACE in terms of colour neutrality – not that of the camera as some people seem to think.

All 3 working colour spaces posses the same degree of colour neutrality where red, green & blue are present at the same values irrespective of physical size of the colour space.

So as long as our monitor is profiled to be:

1. Accurately COLOUR NEUTRAL

2. Displaying maximum brightness only in the presence true white – which you’ll hardly ever photograph, even snow isn’t white.

then we will see a highly workable representation of image colour neutrality and luminosity on our monitor. Only by working this way can we actually tell if the camera has captured the image correctly in terms of colour balance and overall exposure.

And the fact that our monitor CANNOT display all the colours contained within our big ProPhoto bucket is, to all intents and purposes, a fairly mute point; though seeing as many of them as possible is never a bad thing.

And using a monitor that does NOT display the volume of colour approximating or exceeding that of the Adobe working space can be highly detrimental for the reasons discussed in my previous post.

Now that we’ve covered input profiles and working colour spaces we need to move on and outline the basics of output profiles, and printer profiles in particular.

Adobe & sRGB working paces in comparison to the colours contained in the Kingfisher image and the profile for Permajet Oyster paper using the Epson 7900 printer. (CLICK image for full sized view).

In the image above we can see both the Adobe and sRGB working spaces and the full distribution of colours contained in the Kingfisher image which is a TIFF file in our big ProPhoto bucket of colour; and a black trace which is the colour profile (or space if you like) for Permajet Oyster paper using Epson UltraChrome HDR ink on an Epson 7900 printer.

As we can see, some of the colours contained in the image fall outside the gamut of the sRGB working colour space; notably some oranges and “electric blues” which are basically colours of the subject and are most critical to keep in the print.

However, all those ProPhoto colours are capable of being reproduced on the Epson 7900 using Permajet Oyster paper because, as the black trace shows, the printer/ink/paper combination can reproduce colours that lie outside of the Adobe working colour space.

The whole purpose of that particular profile is to ensure that the print matches what we can see on the monitor both in terms of colour and brightness – in other words, what we see is what we get – WYSIWYG!

The beauty of a colour managed workflow is that it’s economical – assuming the image is processed correctly then printing via an accurate printer profile can give you a perfect printed rendition of your screen image using just a single sheet of paper – and only one sheets worth of ink.

The difference between colour profiles for the same printer paper on different printers. Epson 3000 printer profile trace in Red (CLICK image for full size view).

If we were to switch printers to an Epson 3000 using UltraChrome K3 ink on the very same paper, the area circled in white shows us that there are a couple of orange hue colours that are a little problematic – they lie either close to or outside the colour gamut of this printer/ink/paper combination, and so they need to be changed in order to ‘fit’, either by localised adjustment or variation of rendering intent – but that’s a story for later!

Why is it different? Well, it’s not to do with the paper for sure, so it’s down to either the ink change or printer head. Using the same K3 ink in an Epson 4800 brings the colours back into gamut, so the difference is in the printer head itself, or the printer driver, but as I said, it’s a small problem easily fixed.

When you consider the low cost of achieving an accurate monitor profile – see this previous post – and combine that with an accurate printer output profile or two to match your chosen printer papers, and then deploy these assets correctly you have a proper colour managed workflow. Add to that the cost savings in ink and paper and it becomes a bit of a “no-brainer” doesn’t it?

In this post I set out to hopefully ‘demystify’ colour spaces and profiles in terms of what they are and how they are used – I hope I’ve succeeded!

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Monitor Calibration with ColorMunki

Posted on November 28, 2013 by Andrew Astbury

Monitor Calibration with ColorMunki Photo

Following on from my previous posts on the subject of monitor calibration I thought I’d post a fully detailed set of instructions, just to make sure we’re all “singing from the same hymn sheet” so to speak.

Basic Setup

Put the ColorMunki spectrophotometer into the cover/holder and attach the USB cable.

Always keep the sliding dust cover closed when storing the ColorMunki in its holder – this prevents dust ingress which will effect the device performance.

BUT REMEMBER – slide the cover out of the way before you begin the calibration process!

Install the ColorMunki software on your machine, register it via the internet, then check for any available updates.

Once the software is fully installed and working you are ready to begin.

Plug the USB cable into an empty USB port on your computer – NOT an external hub port as this can sometimes cause device/system communication problems.

Launch the ColorMunki software.

The VERY FIRST THING YOU NEED TO DO is open the ColorMunki software preferences and ensure that it looks like the following screen:

PC: File > Preferences

Mac: ColorMunki Photo > Preferences

The value for the Tone Response Curve MUST be set to 2.2 which is the default value.

The ICC Profile Version number MUST be set to v2 for best results – this is NOT the default.

Ensure the two check boxes are “ticked”.**

** These settings can be something of a contentious issue. DDC & LUT check boxes should only be “ticked” if your Monitor/Graphics card combination offers support for these modes.

If you find these settings make your monitor become excessively dark once profiling has been completed, start again ensuring BOTH check boxes are “unticked”.

Untick both boxes if you are working on an iMac or laptop as for the most part these devices support neither function.

For more information on this, a good starting point is a page on the X-Rite website available on the link below:

http://xritephoto.com/ph_product_overview.aspx?ID=1115&Action=Support&SupportID=5561

If you are going to use the ColorMunki to make printer profiles then ensure the ICC Profile Version is set to v2.

By default the ColorMunki writes profiles in ICC v4 – not all computer operating systems can function correctly from a graphics colour aspect; but they can all function perfectly using ICC v2.

You should only need to do this operation once, but any updates from X-Rite, or a re-installation of the software will require you to revisit the preferences panel just to check all is well.

Once this panel is set as above Click OK and you are ready to begin.

Monitor Calibration

This is the main ColorMunki GUI, or graphic user interface:

Click Profile My Display

Select the display you want to profile.

I use what is called a “double desktop” and have two monitors running side by side; if you have just a single monitor connected then that will be the only display you see listed.

Click Next>.

Select the type of display – we are talking here about monitor calibration of a screen attached to a PC or Mac so select LCD.

Laptops – it never hurts a laptop to be calibrated for luminance and colour, but in most cases the graphics output LUT (colour Look Up Table) is barely 8 bit to begin with; the calibration process will usually reduce that to less than 8 bit. This will normally result in the laptop screen colour range being reduced in size and you may well see “virtual” colour banding in your images.

Remedy: DON’T PROCESS ON A LAPTOP – otherwise “me and the boys” will be paying you a visit!

Select Advanced.

Deselect the ambient light measurement option – it can be expensive to set yourself up with proper lighting in order to have an ICC standard viewing/processing environment; daylight (D65) bulbs are fairly cheap and do go a long way towards helping, but the correct amount of light and the colour of the walls and ceiling, and the exclusion of extraneous light sources of incorrect colour temperature (eg windows) can prove somewhat more problematic and costly.

Processing in darkened room without light is by far the easiest, cheapest and most cost-effective way of obtaining correct working conditions.

Set the Luminance target Value to 120 (that’s 120 candelas per square meter if you’re interested!).

Set the Target White Point to D65 (that’s 6500 degrees Kelvin – mean average daylight).

Click Next>.

With the ColorMunki connected to your system this is the screen you will be greeted with.

You need to calibrate the device itself, so follow the illustration and rotate the ColorMunki dial to the indicated position.

Once the device has calibrated itself to its internal calibration tile you will see the displayed GUI change to:

Follow the illustration and return the ColorMunki dial to its measuring position.

Click Next>.

With the ColorMunki in its holder and with the spectrophotometer cover OPEN for measurement, place the ColorMunki on the monitor as indicated on screen and in the image below:

We are now ready to begin the monitor calibration.

Click Next>.

The first thing the ColorMunki does is measure the luminosity of the screen. If you get a manual adjustment prompt such as this (indicates non-support/disabling of DDC preferences option):

Simply turn adjust the monitor brightness slowly until the indicator line is level with the central datum line; you should see a “tick” suddenly appear when the luminance value of 120 is reached by your adjustments.

LCDs are notoriously slow to respond to changes in “backlight brightness” so make an adjustment and give the monitor a few seconds to settle down.

You may have to access your monitor controls via the screen OSD menu, or on Mac via the System Preferences > Display menu.

Once the Brightness/Luminance of the monitor is set correctly then ColorMunki will proceed will proceed with its monitor output colour measurements.

In order for you to understand monitor calibration and what is going on here is a sequence of slides from one of my workshops on colour management:

Once the measurements are complete the GUI will return to the screen in this form.

Either use the default profile name, or one of your own choice and click Save.

NOTE: Under NO CIRCUMSTANCES can you rename the profile after it has been saved, or any other .icc profile for that matter, otherwise the profile will not work.

Click Next>.

Click Save again to commit the new monitor profile to you operating system as the default monitor profile.

You can set the profile reminder interval from the drop down menu.

Click Next>.

Monitor calibration is now complete and you are now back to the ColorMunki startup GUI.

Quit or Exit the ColorMunki application – you are done!

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Monitor Calibration Devices

Posted on November 26, 2013 by Andrew Astbury

Colour management is the simple process of maintaining colour accuracy and consistency between the ACTUAL COLOURS in your image, in terms of Hue, Saturation and Luminosity; and those reproduced on your RGB devices; in this case, displayed on your monitor. Each and every pixel in your image has its very own individual RGB colour values and it is vital to us as photographers that we “SEE” these values accurately displayed on our monitors.

If we were to visit The National Gallery and gaze upon Turners “Fighting Temeraire” we would see all those sumptuous colours on the canvass just as J.M.W. intended; but could we see the same colours if we had a pair of Ray Bans on?

No, we couldn’t; because the sunglasses behave as colour filters and so they would add a “tint” to every colour of light that passes through them.

What you need to understand about your monitor is that it behaves like a filter between your eyes and the recorded colours in your image; and unless that “filter” is 100% neutral in colour, then it will indeed “tint” your displayed image.

So, the first effect of monitor calibration is that the process NEUTRALIZES any colour tint in the monitor display and so shows us the “real colours” in our images; the correct values of Hue and Saturation.

Now imagine we have an old fashioned Kodak Ektachrome colour slide sitting in a projector. If we have the correct wattage bulb in the projector we will see the correct LUMINOSITY of the slide when it is projected.

But if the bulb wattage is too high then the slide will project too brightly, and if the bulb wattage is too low then the projected image will not be bright enough.

All our monitors behave just like a projector, and as such they all have a brightness adjustment which we can directly correlate to our old fashioned slide projector bulb, and this brightness, or backlight control is another aspect of monitor calibration.

Have you done a print that comes out DARKER than the image displayed on the screen?

If you have then your monitor backlight is too bright!

And so, the second effect of monitor calibration is the setting of the correct level of brightness or back lighting of our monitor in order for us to see the true Luminosity of the pixels in our images.

Without accurate Monitor Calibration your ability to control the accuracy of colour and overall brightness of your images is severely limited.

I get asked all the time “what’s the best monitor calibration device to use” so, above is a short video (no sound) I’ve made showing the 3D and 2D plots of profiles I’ve just made for the same monitor using teo different monitor calibration devices/spectrophotometers from opposite ends of the pricing scale.

The first plot you see in black is the AdobeRGB1998 working colour space – this is only shown as a standard by which you can judge the other two profiles; if you like, monitor working colour spaces.

The yellow plot that shows up as an overlay is a profile done with an Xrite ColourMunki Photo, which usually retails for around £300 – and it clearly shows this particular monitor rendering a greater number of colours in certain areas than are contained in the Adobe1998 reference space.

The cyan plot is the same monitor, but profiled with the i1Photo Pro 2 spectro – not much change out of £1300 thank you very much – and the resulting profile virtually an identical twin of the one obtained with the ColorMunki which retails for a quarter of the price!

Don’t get me wrong, the i1 is a far more efficient monitor calibration device if you want to produce custom PRINTER profiles as well, but if you are happy using OEM profiles and just want perfect monitor calibration then I’d say the ColorMunki Photo is the more sensible purchase; or better still the ColorMunki Display at only around £110.

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Monitor, Is Yours Up To The Job?

Posted on November 18, 2013 by Andrew Astbury

Is Your Monitor Actually Up To The Job?

As photographers we have to take something of a “leap of faith” that the monitor we use to view and process our images on is actually up to the job – or do we?

No – is the short answer! As a Photoshop & Lightroom educator I try and teach this mystical thing called “Colour Management” – note the correct spelling of the word COLOUR!

The majority of amateur photographers (and a few so-called pros come to that!) seem to think that colour management is some great complicated edifice; or even some sort of “re-invention of the wheel” – and so they either bury their head in the sand or generally “pooh-pooh” the idea as unnecessary.

Well, it’s certainly NOT complicated, but it certainly IS necessary.

The first stage in a colour managed workflow is to ensure that your monitor is calibrated – in other words it is working at the correct brightness level, and the correct colour balance or white point – this will ensure that when your computer sends pure red to your monitor, pure red is seen on the screen; not red with a blue tint to it!

But correct calibration of your monitor is fairly useless if your monitor cannot reproduce a large variation of colour – in other words, if its’ colour gamut is too small.

And it’s Monitor Colour Gamut that I want to look at in this post.

The first thing I’d like you to do is open up Photoshop and go to the Colour Settings – that’s Edit>Colour Settings, or shift+cmd+K on Mac, or shift+Ctrl+K on PC.

Once this dialogue box is open, set it up as follows:

This is the optimum setup of Photoshop for digital photography as ProPhoto is the best colour space for preserving the largest number of colours captured by your dslr sensor; far better than AdobeRGB1998 – but that’s another story.

If you like you can click the SAVE button and then give this settings profile a name – I call mine ProPhoto_Balanced_CC

Now that you are working with the largest colour palette possible inside Photoshop I want you to go to File>New and created a new 500×500 pixel square with a resolution of 300 pixels per inch with the settings as follows:

Click OK and you should now have a white square.

Now go to your foreground colour, click it to bring the colour palette dialogue box into view and manually add the following values indicated by the small red arrows:

The colour will look a little different than it does in the jpeg above.

So now we have a rather lurid sickly-looking green square in the ProPhoto colour space.

Now duplicate the image TWICE and then go to Window>Arrange>3up Vertical and you should end up with a display looking like this:

Now comes the point of the exercise – click on the tab for the centre image and go Edit>Convert to Profile and choose AdobeRGB(1998) as the destination space (colour space).

Then click on the tab for the left hand image and go Edit>Convert to Profile and choose sRGB as the destination space.

Here’s the thing – if your display DOES NOT look like this:

and all three squares look the same as the square on the left then your monitor only has a small sRGB colour gamut and is going to severely inhibit your ability to process your images properly or with any degree of colour accuracy.

Monitors rely on their Colour Look-up Table or LUT in order to display colour. Calibration of the monitor can reduce the size of the available range of colours in the LUT if it’s not big enough in the first place, and so calibration can indeed make things worse from a colour point of view; BUT, it will still ensure the monitor is set to the correct levels of brightness and colour neutrality; so calibration is still a good idea.

Laptops are usually the best illustration of this small LUT problem; normally their display gamuts are barely 8bit sRGB to begin with, and if calibration drops the LUT to below 8bit then the commonest problem you see is colour banding in your images.

If however, your display looks like the image above then you’re laughing!

Why is a large monitor colour gamut essential for digital photography? Well it’s all to do with those colour spaces:

If you look at the image above you’ll see the three standard primary working colour spaces of ProPhoto, AdobeRGB(1998) and sRGB overlaid for comparison with each other. There’s also a 4th plot – this is the input space of the Canon 1Dx dslr – in other words, it encompasses all the colours the sensor of that camera can record.

In actual fact, some colours can be recorded by the camera that lie OUTSIDE even the ProPhoto colour space!

But you can clearly see that the Adobe space looses more camera-captured colour than ProPhoto – hence RAW file handlers like Lightroom work in Prophoto (or to be more strictly true MelissaRGB – but that’s yet another story!) in order to at least preserve as many of the colours captured by the camera as possible.

Even more camera colour is lost to the sRGB colour space.

So this is why we should always have Photoshop set to a default ProPhoto working space – the archival images we produce will therefore retain as much of the original colours captured by the camera as possible.

If we now turn our attention back to monitors – the windows on to our images – we can now deduce that:

a. If a monitor can only display sRGB at best, then we will only be able to see a small portion of the cameras captured colour.

b. However, if the monitor has a larger colour gamut and a bigger LUT both in terms of colour spectrum and bit depth, then we will see a lot more of the original capture colours – and the more we can see then more effectively we can colour manage.

Monitors are available that can display the Adobe colour gamut, indeed quite a few can display more colours – but if you are on a tight budget these can seem more than expensive to say the least.

A good monitor that I recommend quite a lot – indeed I use one myself – is the HP LP2475W, well worth the price if you can find one; and with a bit of tweaking it will display 98%+ of the AdobeRGB colour space in all three primary colours and even some of the warmer colours that are only ProPhoto:

The green plot is the Adobe space, the red plot is the HP LP2475W display colour space.

So it’s a good buy if you can find one.

However, there’s a catch – there always is! This monitor relies on the LUT of the graphics card driving it – plugged into the modest 512Mb nVidea GT120 on my Mac Pro it is brilliant and competes at every level with the likes of Eizo ColourEdge and NEC Spectraviews for all practical purposes. But plugged into the back of a laptop then it can only reproduce what the lower specification graphics chips can supply it with.

So there we have it, a simple way to test if your monitor is giving you the best advantage when it comes to processing your images – food for thought?

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Andy Astburys' Photography Blog

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Tag Archives: gamma

Monitor Calibration Update

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Monitor Calibration with ColorMunki Photo

Basic Setup

Launch the ColorMunki software.

Monitor Calibration

Remedy: DON’T PROCESS ON A LAPTOP – otherwise “me and the boys” will be paying you a visit!

Please consider supporting this blog.

Monitor Calibration Devices

Without accurate Monitor Calibration your ability to control the accuracy of colour and overall brightness of your images is severely limited.

Monitor, Is Yours Up To The Job?

Is Your Monitor Actually Up To The Job?

Monitor Calibration

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Gamma, Gamma Encoding & Decoding

What is Gamma?

RAW file Gamma

The “Learning Gamma Bear Trap”

Share this post:

Lightroom Tutorials Sample Video Link below: Video will open in a new window

Share this post:

Share this post:

Monitor Calibration with ColorMunki Photo

Basic Setup

Launch the ColorMunki software.

Monitor Calibration

Remedy: DON’T PROCESS ON A LAPTOP – otherwise “me and the boys” will be paying you a visit!

Please consider supporting this blog.

Share this post:

Without accurate Monitor Calibration your ability to control the accuracy of colour and overall brightness of your images is severely limited.

Share this post:

Is Your Monitor Actually Up To The Job?

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