4 replies to this topic

[Marcin_78]

This issue (software binning 2x2 in FireCapture making everything brighter) has been bothering me since a long time because on the site that explains FireCapture settings I had found this info:
 

 

My own images (both astro and daytime) keep showing me something different (in this case it was the camera ZWO ASI482MC + a C-mount lens):
 

 

 

Every setting was the same except for “Bin 2x”, so this option clearly makes everything brighter (some pixels got even over-saturated). How exactly?

 

Thanks in advance!

Edited by Marcin_78, 09 June 2025 - 11:06 AM.

[MJB87]

Moving to an appropriate forum.

[WadeH237]

When you bin 2x2, you are resampling the data, so that the contents of 4 pixels are combined into a single pixel.  Unfortunately, there is no single, correct answer that applies in all cases.

 

When the pixels are combined, the software (or firmware) could simply add the counts together.  This will result in pixels that are literally 4x brighter.  The down side is that it's easier to overflow the maximum pixel value, which leaves that pixel saturated.

 

It's also possible that the software could average the values of the 4 pixels that make up the single pixel.  That would guarantee that the combination does not cause saturation.  It would also leave the apparent brightness of the binned image unchanged.

 

Both of these strategies reduce the camera's effective resolution.

 

In my experience, most of the time, I see the first strategy above, and it looks like that is what you are seeing as well.  I think that there is sufficient evidence in your results to say that the documentation is in error on that point.

[CraigT82]

Yeah binning can be done by averaging the pixels together, or summing them. Both lead to an increase in SNR but in the case of summing you risk saturation and white clipping in the bright areas as each binned pixel is 4x brighter. Looks like firecapture is doing the summing of the pixels in your OP. Not sure if you can’t set it to sum or average in the settings somewhere?

Edit: just seen on the ZWO binning explainer page that software binning in raw8 will sum, whereas binning in raw16 will average. Also there is a post from Torsten in the Firecapture groups forum stating that Firecapture itself does not perform binning, it simply tells the camera to perform the software binning on board, so whether you get average or summed pixels may depend on the make/model of camera or even the driver used.

Edited by CraigT82, 10 June 2025 - 03:08 PM.

[Marcin_78]

Yeah binning can be done by averaging the pixels together, or summing them. Both lead to an increase in SNR but in the case of summing you risk saturation and white clipping in the bright areas as each binned pixel is 4x brighter. Looks like firecapture is doing the summing of the pixels in your OP. Not sure if you can’t set it to sum or average in the settings somewhere?

Edit: just seen on the ZWO binning explainer page that software binning in raw8 will sum, whereas binning in raw16 will average. Also there is a post from Torsten in the Firecapture groups forum stating that Firecapture itself does not perform binning, it simply tells the camera to perform the software binning on board, so whether you get average or summed pixels may depend on the make/model of camera or even the driver used.

 

Thank You! Now it makes sense.