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How Ctp Plate Readers Read Plates

Dedicated plate readers accept a unlike approach to mensuration dot surface area than densitometer How CtP plate readers read plates
Dedicated plate readers accept a unlike approach to mensuration dot surface area than densitometers. What they create it role an internal CCD photographic television camera to accept a continuous musical note photograph of the plate surface area at high resolution in addition to magnification:
Dedicated plate readers accept a unlike approach to mensuration dot surface area than densitometer How CtP plate readers read plates
Depending on the instrument's software in addition to display technology, this master picture may or may non locomote shown to the user.

In corporation to calculate the dot area, most all plate readers role a thresholding algorithm to determine what is the non-printing plate in addition to what is the printing dot.* Put to a greater extent than or less other way, the software decides that a pixel of X musical note score in addition to lighter inwards the captured picture is the plate acre levels darker inwards the captured picture than X musical note score are identified every bit ink carrying dots.

However, because the halftone dots inwards the photograph volition receive got a slight softness to them, the effect is a slight ambiguity every bit to where the transition from non-image plate to ink carrying dot occurs. Change the threshold in addition to you lot alter the size of the dot the musical instrument "sees" in addition to thus the musical note the musical instrument reports.

For event at a threshold value of 139 (from a hit of 0-255), the software sees this every bit the printing dots:
Dedicated plate readers accept a unlike approach to mensuration dot surface area than densitometer How CtP plate readers read platesand reports a dot surface area value of 50%

If the threshold is a musical note value of 175 the software sees this every bit the printing dots:
Dedicated plate readers accept a unlike approach to mensuration dot surface area than densitometer How CtP plate readers read platesand immediately reports a dot surface area value of 55%

So which is best, or to a greater extent than accurate, for mensuration halftone dots on plate? Well, inwards a GATF study of products for mensuration the dot surface area on CTP printing plates (RTR 27: Plate Reading Technologies in addition to Their Performance on CTP Plates) a spectrodensitometer gave real like overall results compared to the best CCD-based solution for plates.

In their defense, dedicated plate readers tin render to a greater extent than information, such every bit halftone frequency in addition to hide angle, than a densitometer when mensuration plates.

* The extremely sophisticated in addition to expensive Jandel planimeter requires the user to describe where they believe the dot edges are inwards corporation to differentiate betwixt plate in addition to dot areas.
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