Monitor calibration for photographers - LCD calibration tests
Calibration methods
Monitor black point and white point
Adjusting black and white point
Gamma and colours
Print matching
Calibration prints
Resolution and aspect ratio
Common monitor resolutions
Hardware pitfalls
Important monitor specs
Stability
Monitor price range
Final thoughts
First up - a quick calibration method
If you are using a Windows system and want to quickly fix your monitor then from your Control Panel open up the Display applet and check that the monitor is working with 24bit colour. Then do a factory reset on the monitor and look at your settings. For example, after a factory reset my Hewlett Packard w1907s has the following settings: Brightness 90%, Contrast 80% and Colour 6500K.
6500K is the colour temperature and is the same colour temperature used by sRGB, the international standard for colour spaces on computer screens and internet documents. Your screen should look quite good now and you will see photos as they will appear on eveyone else's monitor provided they have calibrated to the same standard.
The Factory Reset is a good starting point for calibration because it automatically defaults to a known standard, the sRGB colour space. When calibrating anything you need a baseline from which to measure the effects of any changes you make to your settings.
Using a calibrated monitor under controlled lighting conditions is essential for critically evaluating colour. The rest of this article talks about calibrating an LCD monitor, gamma correction and other general features of LCD monitors.
Monitor calibration methods
Monitors can be calibrated manually using free tools or with a monitor calibrator that will automate the process ensuring more accurate and consistent colour settings. Professional photographers and graphic designers demand the more consistent approach of using a calibrator because it helps them to predict the colour rendition, contrast and tonal ranges in printed work.
This is analagous to the discipline Ansel Adams employed when he would visualise the final print in his mind just before firing the shutter - striving for control over all the variables in the process that can stop you from reaching perfection. However, as we all know, perfection is an illusion and sometimes we just have to be realistic.
Eyeballing test charts doesn't match the precision and consistency of a calibrator but it is educational and gives good results if you know what to look for. Manual calibration is interesting and is another good form of training that increases your understanding of tonality and colour.
Monitor black point and white point
A simple monitor calibration test is to compare the range of tones on a test chart against manual adjustments made with your monitor's brightness and contrast controls. This adjustment fixes your monitor's black and white points before you make a final adjustment that fixes the range of greys in between and tweaks the colours.
Adjusting monitor black point and white point
On computer screens whites should be pure white and black should mean black. We can start looking at our blacks, whites and the intermediate grays using a simple grayscale chart like the one shown below.
If you can see 11 clearly defined squares that increment smoothly from one end to the other then your monitor is displaying good contrast. The greys should be neutral grey and the white square should be a nice milky white with no colour cast.
If the first two squares are indistinguishable then there is something wrong with your blacks and you need to adjust your the monitor brightness setting.
If the last two squares are indistinguishable then there is something wrong with your whites and you need to adjust the monitor contrast setting.
Caveat. At first it might seem counter-intuitive that blacks are adjusted with the brightness control. The brighness control actually adjusts the screen black level and so maybe it would be better for us all if they named it something more appropriate, like for example, 'black level'?.
The above chart is simple and good enough for illustrating the idea but if you want to thoroughly test your eyesight and monitor calibration skills then you will enjoy looking at the Lagom LCD Monitor Test Pages
Monitor gamma and colours
In addition to the black and white point settings monitors have another weird property known as the Gamma Curve. Gamma can affect your colours and tonal range. If you plot this curve on a graph you will find that the relationship between the RGB colour values being sent to the display are not directly related to the intensity of the pixels. This relationship is non linear and each of the RGB colour channels has its own gamma curve that can be adjusted individually using software like Adobe Gamma.
If you have Photoshop installed then you should already have the Adobe Gamma control (look in your Windows Control Panel) that can be used for
calibrating monitor gamma. With the gamma adjustment tool you adjust a slider so that the gray square blends evenly into the background.
The diagram above shows that the monitor is running at 6500K with a gamma correction factor of 2.2. This is the default gamma for Windows systems and is the same gamma I use on Linux. However better tools than Adobe Gamma are available. There is a free application called Quickgamma that uses the gamma chart made by Norman Koren. The Quickgamma web page has some good info on how Gamma correction tools work. Another good resource is the The gamma adjustment page
There is a good step by step Adobe Gamma tutorial with pictures here and they also have a nice Fuji calibration print you can download and use for your tests.
Adobe gamma creates what is called a profile for the monitor. A profile is a file containing a table of numbers that describe the colour characteristics of your particular monitor to the operating system and colour savvy applications like Photoshop and Gimp. The profile acts like a filter that transposes the Gamma curve into a more useful stright line.
Monitor and print colour matching
Ultimately we want to make photographic prints that look the same as the images we see on the monitor. Here is a friendly colour management diagram that illustrates why profiles are used to achieve colour matching between devices. Here is a tutorial from Adobe about getting correct colours from an inkjet printer
Calibration prints
Once your monitor is calibrated you should be getting good prints from your inkjet printer. If you are sending work out for printing then check if your print shop provides a printed calibration image and an equivalent jpeg verson. These are good for visual comparison tests. You compare the calibration print to the electonic version on the screen and you should find that both images are well matched for colour, contrast and tonal range. You can then easily see what your images will look like when they come back from the printers.
This pattern is available from photobox and is helpful when you are using their printing service. They accept Jpeg files in sRGB and their prints are made on quality Fuji photographic paper.
Monitor resolution and picture aspect ratio
Working at the wrong monitor resolution will affect your picture aspect ratio (picture format) and result in distorted images where the proportions are wrong and it feels like you are staring into a fair ground magic mirror. This is due to the different aspect ratios of various monitors. All LCD monitors have a native resolution that you should stick with.
If your LCD resolution is 1600 x 1200 pixels, the your aspect ratio is is 4 : 3.
If you have a 1440 x 900 widescreen then it is 10 : 6 (1440 / 900 = 1.6)
There is a big difference in the aspect ratios
The 4 : 3 format is suitable for most photographers because most cameras save images in 4x3 format. Naturally I prefer the wider monitors because my images are all cropped to 3x2 and I need the length more than the height when viewing and making photos.
Common monitor resolutions
| Monitor Resolution | Picture Aspect Ratio |
| 1600 x 1200 | 4 : 3 |
| 1280 x 1024 | 5 : 4 |
| 1440 x 900 | 16 : 10 |
| 1024 x 768 | 4 : 3 |
| 800 x 600 | 4 : 3 |
I crop my images to a 3:2 format because this format is traditional in photography. Pictures look very different at a 4:3 ratio than at 3:2 because years of using 35mm cameras have conditioned me to prefer the 3x2 format. 35mm negatives were 36mm x 24mm - exactly 3:2.
Hardware pitfalls
Some onboard graphics chips may not work with the native resolution of newer monitors - (1440 x 900 pixels) for example. The chips may work fine with screen resolutions of 1024 x 768 pixels but not have the ability to drive larger resolution monitors. This is easily solved by plugging a graphics card into your PC. It's an easy upgrade and can be cost effective. Juat remember get one with the correct fittings.
Important monitor specifications - what to look for
Native Resolution - the number of pixels the monitor can display, eg 1440 x 900.
Brightness - Look for around 100 Candelas / square metre.
Contrast Ratio - Anything from 700:1 upwards.
Pixel Pitch - Between 0.15 - 0.30mm. The lower the value the sharper the image.
Manual Adjustments - Brightness, Contrast, Colour and Reset.
Monitor stability
LCD monitors remain stable over time and should not need much attention after an initial calibration. Regular attention is recommended for serious work where you are using a colour managed workflow although you may not see much difference in the results of successive calibration tests. CRT monitors (especially older ones) frequently require calibration and this is better done using a calibrator as you will want consistent results and not spend lots of time doing manual calibration with the gamma correction software. As well as being stable LCD monitors are flicker free unlike CRT monitors and they have a consistent tonal range.
Monitor price range
Your budget often determines what size you will buy.
Screen sizes are usually measured diagonally and expressed in inches with sizes ranging from 17" - 24". The cheapest monitors come in sizes from 17" - 19" and they are good enough for most work. They cost between € 150 and € 600. Monitors ranging in size from between 20" - 24" are used a lot by professional photographers, graphic designers and engineering departments. The price of these monitors can range from €1000 and well into the thousands. I have heard some reports of very poor customer service with expensive Samsung monitors and it seems that expensive monitors are just as capable of going on the blink as the lower prices ones.
Final thoughts
Manually calibrating a monitor relies on your eyesight and there is always a doubt about the consistency and accuracy of your calibration results. This is fine for the vast majority of users as it will ensure that they are looking at a monitor that is adjusted to the international sRGB standard for computer monitors and television screens.
A monitor calibrator is recommended for serious amateurs and professionals though because calibrators are very accurate and give consistent results. You plug the calibrator into a USB port, attach the calibrator to the display and press the start button in the calibration program. With manual calibration the question is how much do you trust your eyesight?
