Testing the linearity of the KAF-16803 CCD sensor


Testing the linearity of the KAF-16803 sensor (the anti-blooming version of Kodak’s KAF-16801) seems to reveal a workable photometric range of up to 50% of the sensor’s full well capacity and a ‘comfortable’ upper limit of 40,000 ADU.

The following test data comprises field stars that range significantly in brightness. Exposures at intervals of 5 seconds were acquired up to a maximum of 60 seconds

Screen Shot 2014-07-07 at 12.37.19 pm

Figure 1: Exposure time vs ADU for 4 test stars










Figure 2: shows a plot of the ADU for the peak pixel of each star’s image vs exposure length (click to enlarge).


Figure 2: KAF-16803 linearity test

Bright test stars, such as that used for star 4, are somewhat inconclusive due to the rate in which ADU increases even with modest exposure intervals. A repeat of this test using stars with brightness close to that of star 1 over an extended range of exposure may yield more reliable data.

However, there does appear to be a gradual onset of ‘non-linearity’ at around 40,000 – 50,000 ADU (star 2 & 4)  and strong attenuation beyond 45,000 ADU (star 2 & 3). Of note is the strong linearity trend below 20,000 ADU (star 1) – making it a good candidate for extended testing.

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