Binning and Signal to Noise

stanlep

I have the ASI1600MM camera. The manual says "Hardware binning is supported by sensor but is done in digital domain like software binning and use 10bit ADC."

I do not know what this means. Does it mean the binning is done by software on an image after it is downloaded to the pc? I know nothing about binning.

Also, the manual says "The only advantage of hardware binning is faster fps. We recommend customer to use software binning if you don't care speed."

This implies the camera does both hardware binning but there is also something called software binning. I assume hardware binning means the binning is done on the chip before the image is downloaded to the pc. If this is true, why would the only advantage of hardware binning be fps? From what I have read, on chip binning increases the signal to noise ratio.

Finally, what is software binning? Does it increase the signal to noise ratio?

And does Firecapture allow one to chose between hardware and software binning?

Sincerely,

Stan

Support@ZWO

Hi stanlep

Hard bin is bin in camera, so it will increase fps.

Software bin is bin in software, after data transmit to pc, can not increase fps.

But both hard bin and software bin can increase SNR.

stanlep

I am still uncertain as to whether binning pixels in a CMOS chip increases signal to noise. From what I have read only a hardware bin will increase signal to noise, and from what I have read, a software bin will not increase signal to noise.

Sam (a ZWO employee who responds to questions in this group) in another discussion group said a hardware bin can be specified in FireCapture. However, I have been told that "CMOS has an amp for each pixel thus it can only be binned in software after readout." Therefore, it appears doing a hardware bin is not possible, and therefore only a software bin can be done. This then still raises the issue as to whether signal to noise can be increased by binning.

It also raises a question in my mind as to what is meant by a Hardware bin in the ZWO CMOS camera. Is it really a software bin done at the camera before the frame is sent to the pc?

Can anyone clear up my confusion on this issue?

Stan

Sam@ZWO

hardware bin means binning is done by sensor

and sensor usually skip lines or use less bits ADC to bin pixel and output faster

so you can treat it's software binning in sensor side and not as good as binning in our software

it cannot increase the SNR as "software binning" in our software

so you only need hardware binning when you need faster readout and don't care the final SNR

merlin66

Sam,

You should be aware that Christian Buil has recent carried out a detailed comparison between ATiK CCD and ZWO CMOS cameras.

http://www.astrosurf.com/buil/CMOSvsCCD/index.html

Sam@ZWO

Merlin66 wrote:
Sam,

You should be aware that Christian Buil has recent carried out a detailed comparison between ATiK CCD and ZWO CMOS cameras.

http://www.astrosurf.com/buil/CMOSvsCCD/index.html

that's nice article

but there is misunderstanding:

the SNR I talk is SNR per pixel sample instead of resolution

hs9

Lets first breakdown the impact of hardware binning in CCDs on SNR. There are 2 main impacts:

1. Reduces "shot noise". This is really a property of light and is related to the probabilistic nature of photons. This is the primary benefit of binning.

2. Brings more signal above the read noise threshold hence fainter detail becomes visible in the same exposure time

Now lets see how software binning impacts SNR

1. Software binning i.e. summing adjacent pixels in the digital domain offers exactly the same benefit to shot noise

2. Software binning does not bring more signal over the read noise threshold. But your SNR could still be potentially better than CCDs since the CMOS read noise is so low to begin with.

Overall binning in CMOS offers 90% of the same benefits as CCDs.

Sam@ZWO

Hs9 wrote:
Lets first breakdown the impact of hardware binning in CCDs on SNR. There are 2 main impacts:

1. Reduces "shot noise". This is really a property of light and is related to the probabilistic nature of photons. This is the primary benefit of binning.

2. Brings more signal above the read noise threshold hence fainter detail becomes visible in the same exposure time

Now lets see how software binning impacts SNR

1. Software binning i.e. summing adjacent pixels in the digital domain offers exactly the same benefit to shot noise

2. Software binning does not bring more signal over the read noise threshold. But your SNR could still be potentially better than CCDs since the CMOS read noise is so low to begin with.

Overall binning in CMOS offers 90% of the same benefits as CCDs.

that's very good explanation!