Quote:
Originally Posted by irwjager
Interesting read and I stand corrected regarding hardware binning; "This process is performed prior to digitization in the on-chip circuitry of the CCD by specialized control of the serial and parallel registers." as opposed to in the firmware after digitizing.
You got to wonder though if the increased read noise (4 reads instead of 1 read for 2x2 binning) would really register when performing a single readout per-pixel at the end of a long exposure; you certainly wouldn't hope so!  I can definitely see how this would impact video though. |
Your ideas about binning generally are very wrong there Ivo
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Hardware binning is not done in firmware (but the hardware process is controlled by firmware, totally different). As per ricks excellent link, electrons say in bin 2 are dumped from 2 adjacent pixels into one serial "super pixel" register and read out as one pixel, halving the readout noise. In bin 4 the readout noise is 4 times less, a significant S/N improvement, especially with low signal.
In fact for low signal levels, hardware binning improves read S/N so much it can make the difference between unusable data at bin 1 (due to read noise domination) and more than usable at bin 2.
Many, many times, I have wasted imaging time with bin 1 on dim nebs with 20min exposures with very NB filters and reimaged at bin2 with excellent results.
Your statement avoiding hardware binning and using sofware binning is very missleading, I would say the reverse (from hard experience), software binning is next to useless, its just unnecessary data manipulation for next to no S/N gain at all, and hardware binning is not only necessary, but often critical for any result at all !.
With advanced CCD chips (especially ith ABGs), binning is unlikely to cause saturation as decribed in the link, and anyway, if the signal is so high that blooming occures, then you would simply not need to bin, or take shorter exposures.
Hardware binning is very common BTW, all this is not just my opinion.