www.shopfsi.com

Offset Creation

High quality spectroradiometers offer unsurpassed measurement accuracy when dealing with a wide variety of spectral distributions. However, high quality spectroradiometers are very expensive and measure quite slowly compared to filter based colorimeters. Colorimeters measure very quickly making them ideal for full automatic alignment routines, but without specific offsets for any given spectral distribution can be quite inaccurate. Therefore, at FSI we have adopted a workflow where a high quality spectroradiometer is used as a reference device to which all colorimeters used for automatic alignment are first calibrated with individual offset files for every type of spectral distribution that may be encountered when measuring various FSI monitors. This workflow allows FSI to utilize several fast measuring colorimeters for calibration of new and serviced monitors while maintaining highly accurate measurement results.

FSI's Calibration Workflow

1. FSI offers FREE recalibration of your monitor as often as you like, for as long as you own the monitor, even outside of the warranty period. This is a service many other manufacturers and calibrators charge hundreds of dollars for and represents a significant cost savings to FSI monitor owners. Customers are only responsible for insured freight of the monitor to/from FSI’s service facility in Suwanee, GA, but the full recalibration procedure is performed at no cost. Typical turnaround for this service is within 24 hours of the monitor’s receipt at FSI provided that the monitor is sent into FSI with a valid RMA# issued by FSI’s service department. For customers that own only one or a few FSI monitors this is often the most cost effective recalibration option and ensures that your monitor is professionally recalibrated with the same high quality calibration tools used to calibrate new FSI monitors.
2. FSI sells a CA-210 recalibration kit that includes the DCAA (direct connect automatic alignment) adapter and a Minolta CA-210 colorimeter with preprogrammed recallable spectroradiometer offsets for all current FSI monitor models. The programmed offsets are determined for each individual Minolta CA-210 to ensure the greatest possible accuracy. This option is best suited for larger facilities that own many monitors and can justify the expense of a high quality colorimeter like the CA-210. FSI does not currently interface with any lower end colorimeters for automatic alignment as these cheaper probes tend to track poorly in lowlight measurements, even when offsets are used, making them unsuitable for an automatic alignment routine that measures dark test patches.
3. Customers that already own a CA-210 colorimeter may purchase a DCAA adapter from FSI and send their CA-210 to FSI for calibration of recallable spectroradiometer determined offset files for every current FSI monitor model. Please note that a CA-210 should NOT be used for recalibration of FSI monitors unless it has the proper spectroradiometer determined recallable offsets programmed into the unit.
4. In the USA FSI rents the CA-210 automatic alignment kit. This option is typically much more expensive than sending an individual unit in for recalibration, but for mid-sized facilities with 5 or more monitors renting an alignment kit may make sense both from a financial and convenience standpoint. This program is currently only available in the United States and rental kit availability is limited so customers must first contact FSI to schedule an open timeframe for rental. (This program will begin on a limited basis Summer 2011).
5. All FSI monitors have a simple backlight adjustment that adjusts the unit’s peak white luminance. This is important because the main area of anticipated drift on FSI monitors over time will be the overall luminance of the displays. By simply increasing the backlight setting overtime to maintain consistent peak white luminance most other aspects of display performance will stay within very close tolerances of their original states. Though the x,y chromaticity and CCT readings of puck style colorimeters are generally very inaccurate the peak white luminance reading of a 100% white field is generally fairly accurate, even on lower end colorimeters. These inexpensive probes can therefore be used as basic light meters to maintain a desired luminance level over time. For many applications this adjustment alone will allow the monitor to operate within acceptable tolerance ranges.
6. All FSI monitors are also equipped with basic RGB Gain/Bias controls that allow users with adequate test equipment, such as a high quality spectroradiometer, to manually tweak color temperature on the monitor. This is important because second to peak white luminance some slight drift in overall CCT (x,y chromaticity) is to be expected over time. This drift is typically not substantial, often times being less over the life of a unit than some CRTs would drift in a month, but the adjustments are there for customers interested in these manual tweaks to white balance over time. Customers using this approach should be aware of two important points:
   1. Only slight adjustment to RGB levels should be made. If substantial changes to RGB gain/bias are being used other aspects of calibration may be thrown off considerably. If such changes seem necessary then sending the unit in for complete recalibration may be advisable.
   2. The spectroradiometer used should be of sufficient quality and designed specifically to measure the type of display being calibrated. FSI recommends that spectroradiometers used for this purpose be at least 5nm bandwidth, have at least a 128 element detector, and utilize a high quality lens that allows for sufficient measurement area size at close measuring distances with minimal polarization error. Systems without traditional lenses, for example fiber optic based systems, are not recommended as polarization errors in readings can be significant with such systems on some LCD panel technologies.