download (10)You’ve bought your monitor calibrator, installed and updated the software, connected the measurement instrument and you’re all ready to make your first display profile. Accurate on-screen color is just a click away.

Or is it?

Before calibrating and profiling a monitor for accurate color display, there are a number of ‘pre-flight’ checks you should carry out to ensure that the results you get are as good as possible.

Uniformity assessment: It’s not worth attempting to profile a display if it significantly fades at the corners or has a localised color cast, as any judgements you make will be affected by this. A quick way to visually test uniformity is to set a neutral mid-gray desktop pattern and close all windows. Older-style CRT displays usually have controls that allow you to adjust for mis-aligned screen display and various other screen geometry faults, but there isn’t anything you can do about a faulty LCD panel; be aware that LCD manufacturers do specify tolerances for uniformity and defective pixels.

Clean the screen and position the measuring device: LCD panels don’t attract dust the way electrostatically-charged CRTs did, but it still settles there, and fingerprints won’t help your calibration efforts either. Make sure that if you have a colorimeter with suckers for attaching to glass CRTs that you don’t press it against an LCD panel as it could pull the front membrane off when you remove it. All recent colorimeters for use with LCD displays ship with counterweight arrangements that allow the instrument to rest against the front panel. It usually helps if you tip the screen slightly backwards, to ensure that the colorimeter stays flush to the screen and doesn’t move during measurement.

Resolution and bit-depth settings: LCD panels are best run at their ‘native’ (maximum) resolutions. Most LCD displays support lower resolution modes for compatibility with older video cards, but it may interfere with color rendition as well as image sharpness if you run the display at lower settings. If you’re not certain whether you’re running at maximum, it’s a good idea to check this and that you’re running the display at maximum color (bit) depth – see your operating system help for how to do this, but you should have ‘millions’ of colours, 24- or 32-bit selected.

Display warm-up: It’s crucial that you let your display warm up before attempting to calibrate and profile it. Although CRTs were always known to require a warm-up period to stabilise, it is also true for LCD panels, though once warmed up they then remain more stable than CRTs. Allow at least half an hour.

Energy and screen savers: Disable anything that is likely to change or shut off your screen before beginning profiling. Most screen-saver timings are based on user input activity and won’t necessarily notice that a calibration application is running. Given the warm-up requirement even for LCD panel displays, it makes sense both for calibration purposes and for general working to disable anything that turns the screen off too quickly.

Ambient lighting: Changing the luminance (brightness) on a calibrated display to allow for changes in lighting conditions will invalidate your calibration. Aim to achieve consistent lighting instead. Some display calibration and profiling tools (and some displays) offer ambient light adjustment options that are intended to compensate for changes in the lighting environment. These should never be used.

Arrange things so that the display is the brightest object in your field of view but don’t work in a completely dark room; lighting levels similar to those that are comfortable for watching TV are appropriate. This will help increase the apparent contrast and reveal more shadow details in your images. A monitor hood (included with many high-end models) may be helpful here. When measuring your screen for calibration and profiling, do switch the lights off, draw blinds or curtains, etc, to minimise the chance of stray light getting into the measuring instrument and giving false readings.

Once everything’s set, go ahead and run your calibration and profiling software and enjoy the benefits of accurate color.

This article is based on Practical Colour Management for Photographers and Digital Image Makers, an e-book that’s full of detailed practical tips on how to ‘do’ color management on real computer displays to support high quality image editing. It includes tips on choosing and using colour-critical equipment and the optimum system software settings and working environment for reliable results.

 

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