The image below is useful for evaluating your overall monitor calibration. The first check, obviously, is of overall neutrality. Some monitor calibration systems do a better job at this than than others. The second check is a subjective evaluation of how well your calibration gamma matches with your monitor's native performance. The ideal is smooth gradients from black to white with no banding. A top-notch monitor that is well calibrated can produce this. Most, however, show some level of banding. By matching your calibration gamma value to your monitor, you can significantly reduce banding. This is a good thing for digital image editing, as it allows you to distinguish image flaws from calibration artifacts.
Notes:
- For best results, view the image without passing it through your monitor profile. This is easy on Windows systems, as internet browsers are not color managed by default. On a Mac, OSX allows color managing of web graphics. Internet Explorer assumes untagged images (including the test image below) are in sRGB. You will need to view in Preview or open the file in Photoshop and assign your monitor profile to it. Safari assumes images are in your monitor profile already, so no color management is applied.
- The test image is a PNG file. Some antiquated web browsers do not display PNG images. If yours does not, the same image can be viewed as a GIF graphic. Be warned the file size is 100K, so it may take a while to load.
Neutrality:
- If the entire gradient has a color cast, your monitor is not calibrated adequately. Set the controls to factory defaults, and run your calibration software again. If the problem persists, the calibration hardware may need repair.
- If color crossovers are seen – alternating regions of red, green, or blue – the display calibration is broken. It is possible to create crossovers by tweaking the RGB gun settings on a CRT monitor. Reset your monitor to its factory defaults and calibrate again. If no improvement is seen, your monitor calibrator is incapable of giving good results with your monitor. Some software packages allow building a monitor profile with a single gamma curve rather than individual curves. This can help with lesser quality laptop or other LCD screens. Before chucking your calibration system, however, make absolutely sure you are not viewing the image through a profile.
Banding/Monitor Gamma:
- A very few displays can show the full black to white gradient with no posterization or banding. Most can not. Typically there is some banding in shadows and darker midtones. If the image shows bands throughout the range, either your calibration gamma is not well matched to how your monitor behaves, or you simply have a poor quality display.
- Most modern monitors – Mac or PC – have a native gamma near 2.2. A few specialized displays use other values. The traditional Mac gamma of 1.8 is a holdover from the first monochrome Mac displays. Unless that is what your system uses, your graphics editing environment will benefit from changing to a gamma near 2.2. The only drawback is that the Mac GUI elements – menus, buttons, etc. – are designed for a 1.8 gamma display. These elements will appear darker with a system gamma of 2.2, but images displayed in a color managed system will have fewer display artifacts.
- If you see significant banding and your calibration software allows it, try increasing the gamma by 0.1. There is no hard and fast rule here; if increasing gamma creates more banding, reduce the setting. All monitors we have measured check in at a native gamma of between 1.8 and 2.5.
Direct links to download the above image:
- PNG format (6K)
- GIF format (100K)
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