Linearize an output device
Many output devices, such as imagesetters and printers, have their own calibration utility which will output a test image and perform automatic calibration of the device based on the measurement of the test image. Use this test image for calibration if your device does not have a utility of this kind, or if you want to evaluate the image quality produced by an output service.
Download a high-resolution version in EPS format.
You will need a transmission densitometer or other instrument capable of measuring transmission density.
The test image consists of:
- a grayscale for monitoring changes in dot size between the values output from an application and those actually recorded on film or paper;
- a series of fine lines to check the resolution capability of the device;
- and sample type to check exposure levels.
The grayscale elements go from 5% to 100% in 5% steps and the fine lines from 0.01 points up to 0.1 points.
The procedure for calibrating an imagesetter or other device is as follows:
- Establish the correct exposure level by doing a series of outputs of the test image at different exposure levels. The density of the solid patch should be at least 4.0 (as much as 6.0 for some films), and the type should remain crisp and clear without thickening.
- Having established an exposure level, measure the dot values of each patch. The recorder gain is the difference between the dot value of the output and the dot value specified in the EPS file. This recorder gain can be compensated for in the device calibration utility, or by setting up a transfer function for halftone output.