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Old 30-05-2016, 06:48 PM
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Originally Posted by Shiraz View Post
nope, the read noise goes just the opposite way Greg - it reduces with increasing gain and is lowest at highest gain. However, the effective wells are not very big at high gain, so you need short subs - which you can do because of the low read noise.

The graphs posted earlier and available on the ZWO website show exactly how the various parameters vary with gain. ISO is not used as a measure of gain with these cameras, actual amplifier gain is used. This chip has made a complete transition from the world of DSLRs to the world of CCD measurements.
I wasn't really referring to read noise there Ray but rather overall noise. But yes I thought read noise dropped with higher ISO. Not sure why but I have heard that before.
As far as gain and amplifier in digital cameras there is amplifier gain after a certain point in the ISO in a digital camera. For example the Fuji Xpro 2 starts using amplifier gain at ISO1600. Not sure where the gain comes from below that point, I suppose its digital gain in the ADC.

I don't know about a complete transition as the images I have seen so far seem to have similar constraints - blown out highlights.

A typical DSLR image differs from an Astro CCD image mainly in the stars and highlights. Typically DSLR images have blown stars that are all white with no colour data.

Its worth being aware that this sensor may respond similarly and work around that limitation to avoid images with white stars and blown highlights.

Anyway that is just conjecture and your testing will show these things more clearly.

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