[irwjager (Ivo)]

Originally Posted by Bassnut

Your ideas about binning generally are very wrong there Ivo .

Hardware binning is not done in firmware. 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.

As I have graciously admitted

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.

We're both right! I'm talking from the context from a light polluted site (e.g. lots of skyglow). In that case your read out noise is drowned out by skynoise at relatively short exposure times.

If you're doing your photography from dark sites (lucky you!), read noise definitely becomes an issue and binning can really help.

This is a great read on the subject;
http://www.starrywonders.com/ccdcame...derations.html

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 !.

I take issue with saying that software binning is next to useless though.

For starters, some of us have OSC's and have no way of doing hardware binning without sacrificing color.

Aside from that. The reduction of read noise in hardware binning is merely a (very welcome) side effect of the implementation of binning in the hardware. There are still further benefits to binning, also in the realm of reducing noise. That's why you'll frequently find 'averaging' as one of the binning options in the different software suites.

EDIT: Removed "For example, averaging the 4 pixels in a 2x2 area drops noise by a factor of 2 (it's the same as stacking 4 subs). This can *far* outweigh any read noise gains made by hardware (summing) binning." - It's more complicated than that

As I've said before in this thread, "binning" is just the process of putting multiple samples together and choosing a single sample to represent the multiple samples. This totally leaves open the method/algorithm you chose to assign the single value. There are many ways to avail from the benefits of binning - all of them can be accessed by software and only one (summing) is accessed through hardware (with the added benefit of read out noise reduction).

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.

I was referring to excessive skyglow, not blooming. When you have a lot of skyglow at your site, your wells fill up quickly and skyglow drowns out the signal you're after to the point where everything is overexposed. Binning makes this worse - you collect light faster (4x for 2x2), but for some sensors, your well capacity does not increase by the same factor on all sensors due to ADU limitations; the increased dynamic range you collect can not fully be encoded by the A/D converter. Therefore it is better to record everything you can get, export it to your computer and bin it there. However, if you image very faint objects at dark sites, this is obviously not of concern or use to you at all.

Add to that the flexibility of removing data that you don't want binned and software binning becomes a lot more useful.

That said, hardware binning definitely has its uses and I apologize if I came across as dismissing it completely.