To recalibrate your platemaking process, see the procedures recommended by your plate supplier. In any calibration process, the following procedures are typical:
1. Verifying device linearity
ThermoFlex devices are set up to image linearly (for example, a 10% value in a file is imaged as 10% on the mask, a 50% value is imaged as 50%, and so on). Therefore, it should not be necessary to make any adjustments for device linearity when using a Kodak digital imager. Verifying device linearity is described in Installing the ThermoFlex and setting up mask exposures.
2. Determining optimum main UV exposure time and minimum mask exposure values
Because of oxygen inhibition, it is necessary to determine the minimum mask exposure value that your digital plates will hold. To determine the minimum dot and optimum face exposure time, you must image test targets covering the range of line screens that you will be using.
With these targets you will run a series of back and main UV exposure tests at different exposure times, wash out the plates, and study the results. You should verify the washing out, drying, and post-exposure times for digital plates, because these values may vary from what you are accustomed to using with traditional analog plates.
All exposure times, washout times, and plate results should be confirmed by the media representative who supplies your plates and processing technology. Determining main UV exposure time and minimum mask exposure values is described in Determining UV exposure times and minimum exposure values and Creating bump curves and tone reproduction curves.
3. Creating a bump curve
After establishing the minimum mask exposure value that produces a good printable dot, you must create a bump curve to increase the value of the highlight dots below the minimum exposure value. It may not be necessary to apply a bump curve for all line screens, and using Maxtone and HyperFlex can often eliminate the need for a bump curve.
Creating bump curves is described in Creating bump curves and tone reproduction curves.