Test Cards for Monitor Adjustment

Basic adjustment of monitors and projection systems

How often at photographic club meetings do we hear the comment “It doesn’t look like that on my monitor” when an image is projected? Obviously the fault could be with the projection system (i.e. computer and projector) or with the monitor (i.e. computer and monitor), or both! Consider first what we should do to set up the monitor. But before making any adjustments, you may wish to view the test cards shown below to see just “how far out” your system is.

Click on an image to view larger and to save the jpeg file with an embedded sRGB profile. Note that your browser may not display the file correctly. These should be viewed in an application that is colour aware (i.e. one that recognises and uses the embedded profile).

Colour Test Card © John Widdall 1. Colour steps – From 0% (black) to 100% (white, red, green, blue) in steps of 5%

Click on the image to view larger. A difference in luminance should be visible between every step. Look particularly at the ends of the stepped wedges – 0% to 5% and 95% to 100%. The lower levels of blue are usually difficult to see but a difference between 0% (black) and 5% should be perceptible. If necessary reduce the ambient light level – daylight might be alright for word processing but for image processing a much lower level is required. Note that the 0% (black) patches are the same colour as the background. Also, this test card is not intended for assessing colour saturation or colour balance.

Shadow and Highlight Test Card © John Widdall2. Shadow and highlight test – Steps of 4 digits (about 1.5%) from black (0) and from white (255)

Click on the image to view larger. This test card allows closer inpection of shadow and highlight performance. There should be visible dark, but not black, patches labelled 4, 8, 12, 16, against a black background (value = 0) and distinctly different light patches labelled 239, 243, 247, 251, against a white background (value = 255).

If your monitor does not display the test cards correctly, consider re-calibrating your monitor and, if necessary, re-profiling your system (i.e. computer and monitor). I say “if necessary” because if you have not previously profiled your system, you may decide that it is good enough without, once the monitor has been calibrated.

Calibration

This refers to making adjustments to the monitor itself, usually via an “on screen display” (OSD), to bring the monitor to a standard state. Before doing this it is worth considering the factors which affect the appearance of the test card (or any other displayed image). These are:

1. Screen resolution and bit depth. In the system settings, make sure that the screen resolution is correct for your monitor (consult the monitor handbook if necessary) and that the bit depth is maximum.

2. Colour space. The appropriate colour space profile must be used to view the image file. The test cards on this site are jpeg files with the sRGB profile. They should display correctly in a browser which is “colour aware” (e.g. Firefox if properly set up) but to be sure it is best to view them in a graphics application with which you are familiar.

3. Monitor profile (in the computer). A monitor profile may be loaded at startup of the computer This may need to be unloaded before calibrating the monitor.

4. Graphics card settings. Any changes made in the graphics card’s Control Panel need to be reset to their default values. These can usually be accessed via your system settings – look for “NVIDIA Control Panel” or whatever brand of graphics card your system uses. In my system the default values are Brightness 50%, Digital Vibrance 0%, Contrast 50%, Gamma 1.00. You might think we want a gamma value of 2.2 but the monitor should have a target value of 2.2 built in which is, in effect, multiplied by the value set in the graphics card, which should therefore be left at 1.00.

All the above are in the computer. Do not make any changes to the graphics card settings unless you intend to proceed to calibrate and/or profile your system.

Decisions – Some like it hot (i.e. cool)

LCD monitors usually offer you a choice of Colour Temperature as well as the obvious Brightness and Contrast.  (Black level and Backlight may also be present). Colour Temperature is usually specified as a temperature in Kelvin. The sRGB specification quotes a figure of 6500K which means that the white of the monitor is the same colour as an object at that temperature. Oddly, to obtain a “warmer” white we reduce the colour temperature (think of a tungsten lamp on a dimmer – as you turn it down it goes redder). You don’t have to use 6500K, if you are a printer you might choose a lower value so that the screen image more closely matches the print when viewed in a tungsten halogen bulb – these are available with a colour temperature up to 5000K. A monitor calibrated to 5000K looks a bit yellow, so I calibrate to 6500K, often referred to as D65.

Having decided on the colour of the white point, you must decide on the luminance (i.e. how bright). The sRGB specification states 80Cd/m². If you are happy with your current setting leave it. Adjusting Brightness (or Black level) and Contrast whilst viewing the test cards should allow you to achieve a comfortable white level with detail in the highlights whilst retaining detail in the shadows. If you can achieve this then do not worry about the actual measured value.

Adjusting Gamma

All that remains is to check the value of gamma. Briefly, this relates to the level of the mid-tones. This can be checked visually using a special test chart. I recommend the one on The Lagom LCD monitor test pages.  You may want to read my page on Gamma Measurement – a simple method for measuring gamma is described.

If adjustment is necessary and you have access to a profiling device you might decide to take the profiling route, alternatively you could adjust gamma in the graphics driver’s control panel (mentioned at point 4 above). A small change from 1.00 to 0.95 or 1.05 may be all that is required.

Profiling (often referred to as Characterisation)

Profiling is optional and requires a colorimeter or spectrophotometer. A profile provides “fine tuning” of the calibrated monitor’s response. This means that if you generate a profile any subsequent adjustment of the monitor’s brightness, contrast etc. will invalidate that profile, as will any change to the graphics driver’s settings.

If you have a profiling system … follow the process described in the commercial software supplied but when you are confident, try the FLOSS (Free, Libre, Open Source Software), Dispcal GUI which uses the Argyll CMS software. This takes longer to generate a profile but the result is far superior to the software supplied with the colorimeter. Having switched to Linux a few years ago – I abandoned my other OS when XP finally expired – I tried DispcalGUI with the Spyder 3 colorimeter and now have a pair of monitors which match better than they have ever done.

Further Reading

Argyllcms – The Colour Management Software used by DispcalGUI

DispcalGUI – Open Source Software which uses commercial colorimeters (Datacolor Spyder series, X-rite Colormunki series and others)

Calibration vs. Characterization – Explanation of the terms as used by Argyll and DispGUI.

Nine Degrees Below – Elle Stone’s website – Articles on Colour Management in Photography including:

Profiling Your Monitor — Popular Confusions, Hopefully Cleared

Two articles by Jim Perkins, aimed at illustrators rather than photographers but very relevant:

Real professionals calibrate their computer screens. Do you?

Gamma and White Point Explained: How to Calibrate Your Monitor

© John Widdall 2008-2015 (Test Cards first published 2008, Page completely revised September 2015).

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