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Old 25-03-2016, 02:51 AM
glend (Glen)
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glend is offline
Join Date: Jun 2013
Location: Lake Macquarie
Posts: 5,396
It would be worthwhile to consider the Quantum Efficiency of any potential DSLR purchased for astrophotography work. Here is a link to an old study by DPReview that covers the older Canon models (typically used by those of us that modify them):

Under this review the 450D delivered a QE of 30.4%, the Nikon D3 at 40.2%.

There is another very useful link here:

This link by Roger Clark for Clarkvision, covers everything pretty well and includes a useful "Sensor Full Well" chart by camera model, and SNR over pixel pitch, and sensor read noise charts. The typical Canon models disucssed showed significantly less Read Noise than the Nikon's tested, but I think the Nikon D3 was actually the best in this category grouping in with the Canons. Importantly the CMOS sensors all showed less read noise than the CCDs examined, including the venerable KAF-8300.
From the Dynamic Range chart, it is clear that Dynamic Range drops as ISO goes up. Clark observes that "ISO is simply a post sensor gain followed by digitisation. ISO settings are needed mainly to compensate for inadequate dynamic range of downstream elecronics".
The Thermal Noise from Dark Current Chart is informative, clearly showing the benefits of keeping the sensor cooled; and this backs up research under taken by rchesire (Rowland) here in his thread on IIS on Cold Finger Cooled DSLRs in the DIY forum. Rowland showed through Dark and Bias Frame comparisons that cooling a 450D sensor (with 5.2 micron pixels) to 0C produced the best solution for elimination fo Dark Current Noise; this was also confirmed by my own comparisons on my cooled 450D.
This indepth study by Clark is good holiday reading and provides a tutorial to all the terms of reference in DSLR performance.

BTW, this thread topic was also the subject of a Cloudy Nights thread here:

Last edited by glend; 25-03-2016 at 08:45 AM.
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