Tag Archives: contrast

Pixel Resolution

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What do we mean by Pixel Resolution?

Digital images have two sets of dimensions – physical size or linear dimension (inches, centimeters etc) and pixel dimensions (long edge & short edge).

The physical dimensions are simple enough to understand – the image is so many inches long by so many inches wide.

Pixel dimension is straightforward too – ‘x’ pixels long by ‘y’ pixels wide.

If we divide the physical dimensions by the pixel dimensions we arrive at the PIXEL RESOLUTION.

Let’s say, for example, we have an image with pixel dimensions of 3000 x 2400 pixels, and a physical, linear dimension of 10 x 8 inches.

Therefore:

3000 pixels/10 inches = 300 pixels per inch, or 300PPI

and obviously:

2400 pixels/8 inches = 300 pixels per inch, or 300PPI

So our image has a pixel resolution of 300PPI.

 

How Does Pixel Resolution Influence Image Quality?

In order to answer that question let’s look at the following illustration:

Andy Astbury,pixels,resolution,dpi,ppi,wildlife in pixels

The number of pixels contained in an image of a particular physical size has a massive effect on image quality. CLICK to view full size.

All 7 square images are 0.5 x 0.5 inches square.  The image on the left has 128 pixels per 0.5 inch of physical dimension, therefore its PIXEL RESOLUTION is 2 x 128 PPI (pixels per inch), or 256PPI.

As we move from left to right we halve the number of pixels contained in the image whilst maintaining the physical size of the image – 0.5″ x 0.5″ – so the pixels in effect become larger, and the pixel resolution becomes lower.

The fewer the pixels we have then the less detail we can see – all the way down to the image on the right where the pixel resolution is just 4PPI (2 pixels per 0.5 inch of edge dimension).

The thing to remember about a pixel is this – a single pixel can only contain 1 overall value for hue, saturation and brightness, and from a visual point of view it’s as flat as a pancake in terms of colour and tonality.

So, the more pixels we can have between point A and point B in our image the more variation of colour and tonality we can create.

Greater colour and tonal variation means we preserve MORE DETAIL and we have a greater potential for IMAGE SHARPNESS.

REALITY

So we have our 3 variables; image linear dimension, image pixel dimension and pixel resolution.

In our typical digital work flow the pixel dimension is derived from the the photosite dimension of our camera sensor – so this value is fixed.

All RAW file handlers like Lightroom, ACR etc;  all default to a native pixel resolution of 300PPI. * (this 300ppi myth annoys the hell out of me and I’ll explain all in another post).

So basically the pixel dimension and default resolution SET the image linear dimension.

If our image is destined for PRINT then this fact has some serious ramifications; but if our image is destined for digital display then the implications are very different.

 

Pixel Resolution and Web JPEGS.

Consider the two jpegs below, both derived from the same RAW file:

Andy Astbury,pixels,resolution,dpi,ppi,Wildlife in Pixels

European Adder – 900 x 599 pixels with a pixel resolution of 300PPI

European Adder - 900 x 599 pixels with a pixel resolution of 72PPI

European Adder – 900 x 599 pixels with a pixel resolution of 72PPI

In order to illustrate the three values of linear dimension, pixel dimension and pixel resolution of the two images let’s look at them side by side in Photoshop:

Andy Astbury,photoshop,resolution,pixels,ppi,dpi,wildlife in pixels,image size,image resolution

The two images opened in Photoshop – note the image size dialogue contents – CLICK to view full size.

The two images differ in one respect – their pixel resolutions.  The top Adder is 300PPI, the lower one has a resolution of 72PPI.

The simple fact that these two images appear to be exactly the same size on this page means that, for DIGITAL display the pixel resolution is meaningless when it comes to ‘how big the image is’ on the screen – what makes them appear the same size is their identical pixel dimensions of 900 x 599 pixels.

Digital display devices such as monitors, ipads, laptop monitors etc; are all PIXEL DIMENSION dependent.  The do not understand inches or centimeters, and they display images AT THEIR OWN resolution.

Typical displays and their pixel resolutions:

  • 24″ monitor = typically 75 to 95 PPI
  • 27″ iMac display = 109 PPI
  • iPad 3 or 4 = 264 PPI
  • 15″ Retina Display = 220 PPI
  • Nikon D4 LCD = 494 PPI

Just so that you are sure to understand the implication of what I’ve just said – you CAN NOT see your images at their NATIVE 300 PPI resolution when you are working on them.  Typically you’ll work on your images whilst viewing them at about 1/3rd native pixel resolution.

Yes, you can see 2/3rds native on a 15″ MacBook Pro Retina – but who the hell wants to do this – the display area is minuscule and its display gamut is pathetically small. 😉

Getting back to the two Adder images, you’ll notice that the one thing that does change with pixel resolution is the linear dimensions.

Whilst the 300 PPI version is a tiny 3″ x 2″ image, the 72 PPI version is a whopping 12″ x 8″ by comparison – now you can perhaps understand why I said earlier that the implications of pixel resolution for print are fundamental.

Just FYI – when I decide I’m going to create a small jpeg to post on my website, blog, a forum, Flickr or whatever – I NEVER ‘down sample’ to the usual 72 PPI that get’s touted around by idiots and no-nothing fools as “the essential thing to do”.

What a waste of time and effort!

Exporting a small jpeg at ‘full pixel resolution’ misses out the unnecessary step of down sampling and has an added bonus – anyone trying to send the image direct from browser to a printer ends up with a print the size of a matchbox, not a full sheet of A4.

It won’t stop image theft – but it does confuse ’em!

I’ve got a lot more to say on the topic of resolution and I’ll continue in a later post, but there is one thing related to PPI that is my biggest ‘pet peeve’:

 

PPI and DPI – They Are NOT The Same Thing

Nothing makes my blood boil more than the persistent ‘mix up’ between pixels per inch and dots per inch.

Pixels per inch is EXACTLY what we’ve looked at here – PIXEL RESOLUTION; and it has got absolutely NOTHING to do with dots per inch, which is a measure of printer OUTPUT resolution.

Take a look inside your printer driver; here we are inside the driver for an Epson 3000 printer:

Andy Astbury,printer,dots per inch,dpi,pixels per inch,ppi,photoshop,lightroom,pixel resolution,output resoloution

The Printer Driver for the Epson 3000 printer. Inside the print settings we can see the output resolutions in DPI – Dots Per Inch.

Images would be really tiny if those resolutions were anything to do with pixel density.

It surprises a lot of people when they come to the realisation that pixels are huge in comparison to printer dots – yes, it can take nearly 400 printer dots (20 dots square) to print 1 square pixel in an image at 300 PPI native.

See you in my next post!

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Bit Depth

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Bit Depth – What is a Bit?

Good question – from a layman’s point of view it’s the smallest USEFUL unit of computer/digital information; useful in the fact that it can have two values – 0 or 1.

Think of it as a light switch; it has two positions – ON and OFF, 1 or 0.

bit, Andy Astbury, bit depth

A bit is like a light switch.

We have 1 switch (bit) with 2 potential positions (bit value 0 or 1) so we have a bit depth of 1. We can arrive at this by simple maths – number of switch positions to the power of the number of switches; in other words 2 to the 1st power.

How Does Bit Depth Impact Our Images:

So what would this bit depth of 1 mean in image terms:

Andy Astbury,bit depth,

An Image with a Bit Depth of 1 bit.

Well, it’s not going to win Wildlife Photographer of the Year is it!

Because each pixel in the image can only be black or white, on or off, 0 or 1 then we only have two tones we can use to describe the entire image.

Now if we were to add another bit to the overall bit depth of the image we would have 2 switches (bits) each with 2 potential values so the total number of potential values, so 2 to the 2nd, or 4 potential output values/tones.

Andy Astbury,bits,bit depth

An image with a bit depth of 2 bits.

Not brilliant – but it’s getting there!

If we now double the bit depth again, this time to 4 bit, then we have 2 to the 4th, or 16 potential tones or output values per image pixel:

Andy Astbury,bits,bit depth

A bit depth of 4 bits gives us 16 tonal values.

And if we double the bit depth again, up to 8 bit we will end up with 2 to the 8th power, or 256 tonal values for each image pixel:

Andy Astbury,bits,bit depth

A bit depth of 8 bits yields what the eye perceives to be continuous unbroken tone.

This range of 256 tones (0 to 255) is the smallest number of tonal values that the human eye can perceive as being continuous in nature; therefore we see an unbroken range of greys from black to white.

More Bits is GOOD

Why do we need to use bit depths HIGHER than 8 bit?

Our modern digital cameras capture and store RAW images to a bit depth of 12 bit, and now in most cases 14 bit – 4096 & 16,384 tonal values respectively.

Just as we use the ProPhotoRGB colour space to preserve as many CAPTURED COLOURS as we can, we need to apply a bit depth to our pixel-based images that is higher than the capture depth in order to preserve the CAPTURED TONAL RANGE.

It’s the “bigger bucket” or “more stairs on the staircase” scenario all over again – more information about a pixels brightness and colour is GOOD.

Andy Astbury,bits,bit depth,tonal range,tonality,tonal graduation

How Tonal Graduation Increases with Bit Depth.

Black is black, and white is white, but increased bit depth gives us a higher number of steps/tones; tonal graduations, to get from black to white and vice versa.

So, if our camera captures at 14 bit we need a 15 bit or 16 bit “bucket” to keep it in.  And for those who want to know why a 14 bit bucket ISN’T a good idea then try carrying 2 gallons of water in a 2 gallon bucket without spillage!

The 8 bit Image Killer

Below we have two identical grey scale images open in Photoshop – simple graduations from black to white; one is a 16 bit image, the other 8 bit:

Andy Astbury,bits,bit depth,tone,tonal graduation

16 bit greyscale at the top. 8 bit greyscale below – CLICK Image to view full size.

Now everything looks OK at this “fit to screen” magnification; and it doesn’t look so bad at 1:1 either, but let’s increase the magnification to 1600% so we can see every pixel:

 

Andy Astbury,bits,bit depth,tone,tonal range,tonal graduation

CLICK Image to view full size. At 1600% magnification we can see that the 8 bit file is degraded.

At this degree of magnification we can see a huge amount of image degradation in the lower, 8 bit image whereas the upper, 16 bit image looks tonally smooth in its graduation.

The degradation in the 8 bit image is simply due to the fact that the total number of tones is “capped” at 256. and 256 steps to get from the black to the white values of the image are not sufficient – this leaves gaps in the image that Photoshop has to fill with “invented” tonal information based on its own internal “logic”….mmmmmm….

There was a time when I thought “girlies” were the most illogical things on the planet; but since Photoshop, now I’m not so sure…!

The image is a GREYSCALE – RGB ratios are supposedly equal in every pixel, but as you can see, Photoshop begins to skew the ratios where it has to do its “inventing” so we not only have luminosity artifacts, but we have colour artifacts being generated too.

You might look upon this as “pixel peeping” and “geekey”, but when it comes to image quality, being a pixel-peeping Geek is never a bad thing.

Of course, we all know 8bit as being “jpeg”, and these artifacts won’t show up on a web-based jpeg for your website; but if you are in the business of large scale gallery prints, then printing from an 8 bit image file is never going to be a good idea as these artifacts WILL show on the final print.

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How White is Paper White?

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What is Paper White?

We should all know by now that, in RGB terms, BLACK is 0,0,0 and that WHITE is 255,255,255 when expressed in 8 bit colour values.

White can also be 32,768: 32,768: 32,768 when viewed in Photoshop as part of a 16 bit image (though those values are actually 15 bit – yet another story!).

Either way, WHITE is WHITE; or is it?

paper white,photo paper white,printing paper white,Permajet paper whites, snow, Arctic Fox

Arctic Fox in Deep Snow ©Andy Astbury/Wildlife in Pixels

Take this Arctic Fox image – is anything actually white?  No, far from it! The brightest area of snow is around 238,238,238 which is neutral, but it’s not white but a very light grey.  And we won’t even discuss the “whiteness” of  the fox itself.

paper white,photo paper white,printing paper white,Permajet paper whites, bird, pheasant, snow

Hen Pheasant in Snow ©Andy Astbury/Wildlife in Pixels

The Hen Pheasant above was shot very late on a winters afternoon when the sun was at a very low angle directly behind me – the colour temperature has gone through the roof and everything has taken on a very warm glow which adds to the atmosphere of the image.

paper white,photo paper white,printing paper white,Permajet paper whites, snow, sunset, extreme colour temperature

Extremes of colour temperature – Snow Drift at Sunset ©Andy Astbury/Wildlife in Pixels

We can take the ‘snow at sunset’ idea even further, where the suns rays strike the snow it lights up pink, but the shadows go a deep rich aquamarine blue – what we might call a ‘crossed curves’ scenario, where shadow and lower mid tones are at a low Kelvin temperature, and upper mid tones and highlights are at a much higher Kelvin.

All three of these images might look a little bit ‘too much’ – but try clicking one and viewing it on a darker background without the distractions of the rest of the page – GO ON, TRY IT.

Showing you these three images has a couple of purposes:

Firstly, to show you that “TRUE WHITE” is something you will rarely, if ever, photograph.

Secondly, viewing the same image in a different environment changes the eyes perception of the image.

The secondary purpose is the most important – and it’s all to do with perception; and to put it bluntly, the pack of lies that your eyes and brain lead you to believe is the truth.

Only Mother Nature, wildlife and cameras tell the truth!

So Where’s All This Going Andy, and What’s it got to do with Paper White?

Fair question, but bare with me!

If we go to the camera shop and peruse a selection of printer papers or unprinted paper samplers, our eyes tell us that we are looking at blank sheets of white paper;  but ARE WE?

Each individual sheet of paper appears to be white, but we see very subtle differences which we put down to paper finish.

But if we put a selection of, say Permajet papers together and compare them with ‘true RGB white’ we see the truth of the matter:

paper white,photo paper white,printing paper white,Permajet paper whites

Paper whites of a few Permajet papers in comparison to RGB white – all colour values are 8bit.

Holy Mary Mother of God!!!!!!!!!!!!!!!!

I’ll bet that’s come as a bit of a shocker………

No paper is WHITE; some papers are “warm”; and some are “cool”.

So, if we have a “warmish” toned image it’s going to be a lot easier to “soft proof” that image to a “warm paper” than a cool one – with the result of greater colour reproduction accuracy.

If we were to try and print a “cool” image on to “warm paper” then we’ve got to shift the whole colour balance of the image, in other words warm it up in order for the final print to be perceived as neutral – don’t forget, that sheet of paper looked neutral to you when you stuck it in the printer!

Well, that’s simple enough you might think, but you’d be very, very wrong…

We see colour on a print because the inks allow use to see the paper white through them, but only up to a point.  As colours and tones become darker on our print we see less “paper white” and more reflected colour from the ink surface.

If we shift the colour balance of the entire image – in this case warm it up – we shift the highlight areas so they match the paper white; but we also shift the shadows and darker tones.  These darker areas hide paper white so the colour shift in those areas is most definitely NOT desirable because we want them to be as perceptually neutral as the highlights.

What we need to do in truth is to somehow warm up the higher tonal values while at the same time keep the lowest tonal values the same, and then somehow match all the tones in between the shadows and highlights to the paper.

This is part of the process called SOFT PROOFING – but the job would be a lot easier if we chose to print on a paper whose “paper white” matched the overall image a little more closely.

The Other Kick in the Teeth

Not only are we battling the hue of paper white, or tint if you like, but we also have to take into account the luminance values of the paper – in other words just how “bright” it is.

Those RGB values of paper whites across a spread of Permajet papers – here they are again to save you scrolling back:

paper white,photo paper white,printing paper white,Permajet paper whites

Paper whites of a few Permajet papers in comparrison to RGB white – all colour values are 8bit.

not only tell us that there is a tint to the paper due to the three colour channel values being unequal, but they also tell us the brightest value we can “print” – in other words not lay any ink down!

Take Oyster for example; a cracking all-round general printer paper that has a very large colour gamut and is excellent value for money – Permajet deserve a medal for this paper in my opinion because it’s economical and epic!

Its paper white is on average 240 Red, 245 Green ,244 Blue.  If we have any detail in areas of our image that are above 240, 240, 240 then part of that detail will be lost in the print because the red channel minimum density (d-min) tops out at 240; so anything that is 241 red or higher will just not be printed and will show as 240 Red in the paper white.

Again, this is a problem mitigated in the soft proofing process.

But it’s also one of the reasons why the majority of photographers are disappointed with their prints – they look good on screen because they are being displayed with a tonal range of 0 to 255, but printed they just look dull, flat and generally awful.

Just another reason for adopting a Colour Managed Work Flow!

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Colour Space & Profiles

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colour space

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:

colour space volume

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:

colour space

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.

colour space, profile, print profile

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.

colour space, colour profile

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

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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

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

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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!

colormunkiSpecCover

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

Screen Shot 2013-10-17 at 11.28.32

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:

Screen Shot 2013-10-17 at 12.32.58

Click Profile My Display

Screen Shot 2013-10-17 at 11.17.49

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>.

Screen Shot 2013-10-17 at 11.18.18

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>.

Screen Shot 2013-10-17 at 11.19.44

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:

Screen Shot 2013-10-17 at 11.20.26

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

Screen Shot 2013-10-17 at 11.20.49

Click Next>.

Screen Shot 2013-10-17 at 11.21.11

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:

XR-CLRMNK-01

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):

ColorMunki-Photo-display-screen-111

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:

moncal1

moncal2

moncal3

moncal4

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

Screen Shot 2013-10-17 at 11.26.29

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>.

Screen Shot 2013-10-17 at 11.27.00

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>.

Screen Shot 2013-10-17 at 12.32.58

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

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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?

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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:

Screen Shot 2013-11-18 at 13.47.30

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:

Screen Shot 2013-11-18 at 13.58.34

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:

Screen Shot 2013-11-18 at 14.06.52

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:

unconverted

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:

MonitorColourDisplay

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:

Screen Shot 2013-11-18 at 14.56.11

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:

Screen Shot 2013-11-18 at 15.40.07

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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