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 Post Posted: Fri Sep 22, 2017 12:17 am 
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Sam,
I compared some of the ASI290's 16bit unbinned and x2 binned images and I did not see the change in brightness levels I expected. For comparison I took an unbinned capture and ran it through my binning script and the results were totally different for x2 bin.

It seems that the ZWO SDK is performing an average / mean function instead of a sum when you select x2 bin in 16 bit mode. If so, can you fix this. This is really problematic.

Thanks


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 Post Posted: Sat Sep 23, 2017 5:27 am 
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Hs9 wrote:
Sam,
I compared some of the ASI290's 16bit unbinned and x2 binned images and I did not see the change in brightness levels I expected. For comparison I took an unbinned capture and ran it through my binning script and the results were totally different for x2 bin.

It seems that the ZWO SDK is performing an average / mean function instead of a sum when you select x2 bin in 16 bit mode. If so, can you fix this. This is really problematic.

Thanks

290 has only 12bit ADC, we put the 12bit data in front of 16bit data
software use the high 8bit to display the image

it become 14 bit after bin2
but we still put the 14bit data in front of 16bit data
and software still use the high 8bit to display the image
so brightness donot change

but if you run under RAW8
software choose the high 8bit of 12bit data to display
and the data become 10bit after bin2
but software choose the low 8bit to display

you can do it by yourself if you want to see brightness changes after binning

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 Post Posted: Tue Sep 26, 2017 9:23 pm 
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Sam,
I ran the pixel math and I am pretty sure that in raw16 mode the driver is averaging/taking a mean and not binning.

Just to be sure that I was using the latest SDK I went to ZWO website to download the latest version and I saw this in the change log (http://astronomy-imaging-camera.com/sof ... ASISDK.txt):

V1.13.0.7 2016.12.13
Add support for ASI071MC-Cool
Add control ANTI_DEW_HEATER
Add API ASIGetProductIDs for all supported cameras
Fan is on when cooler works and turn off when cooler stop work
The ID get from ASIGetCameraProperty become const even refreshing devices
Binning pixel value is changed to the sum of bin*bin pixels at 8bit, and keep as the mean value for 16bit
Fix the serration issue at bin mode for color camera


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 Post Posted: Sat Sep 30, 2017 12:23 am 
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just check with our guys
you are correct we use average when binning under RAW16
because there is bin3 and bin4, sum up may saturate

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 Post Posted: Sat Sep 30, 2017 4:15 pm 
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Thanks Sam. I would think saturation risk from binning would be higher in RAW8 vs. RAW16. In fact it is unlikely you will saturate when using RAW16 and x2 or x3 software binning (as long as the individual frames are not saturated).

The highest level you can get by x2 binning (assuming 12bit o/p) is 4096 x 4 = 16384

Similarly the highest level you can get by x3 binning is 4096 x 9 = 36864

Significantly lower than the 65536 levels that 16bit image can accommodate.

Would appreciate if you can fix the binning to do sum in RAW16 mode. This is a highly desired feature by many on the EAA as well as imaging forums. In fact ZWO's implementation has resulted in other camera manufacturers incorporating sum binning in their software.


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 Post Posted: Thu Oct 05, 2017 1:39 am 
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Hs9 wrote:
Thanks Sam. I would think saturation risk from binning would be higher in RAW8 vs. RAW16. In fact it is unlikely you will saturate when using RAW16 and x2 or x3 software binning (as long as the individual frames are not saturated).

The highest level you can get by x2 binning (assuming 12bit o/p) is 4096 x 4 = 16384

Similarly the highest level you can get by x3 binning is 4096 x 9 = 36864

Significantly lower than the 65536 levels that 16bit image can accommodate.

Would appreciate if you can fix the binning to do sum in RAW16 mode. This is a highly desired feature by many on the EAA as well as imaging forums. In fact ZWO's implementation has resulted in other camera manufacturers incorporating sum binning in their software.


actually there is no difference with sum up or average because you can turn up gain
I personally would like to use average even under 8bit

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 Post Posted: Thu Oct 05, 2017 3:06 pm 
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Sam,

Binning is defined as a sum operation in all texts. Doing an average is primarily a way for increasing frame rate for security camera application and is not binning. Averaging is not very useful for Astro camera applications.

It also quite easy to show mathematically that using higher gain is not equivalent to binning as using higher gain brings the ADC into play leading to quantization considerations.

Further, information loss happens when I save binned files. Since the File formats cannot store floating point values, the rounding results in significant loss of information. I have experienced this and can demonstrate this quite easily for you.

For decades, even in professional Astro applications binning has been defined as summing pixels. Many of the Photometry scripts I use depend on it.

ZWO's insistance on using a non standard operation and calling it binning is not helpful and is causing a lot of confusion. I really don't understand your insistence on sticking with averaging. There are no saturation concerns in 16 bit mode even if you bin x4. Anyways as the camera manufacturer you should let the user manage saturation concerns if any.

I hope you fix this.

Hiten


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 Post Posted: Thu Oct 05, 2017 5:12 pm 
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Hi Sam,
Hi Hiten,

Interesting post because my opinion is exactly the same as Hiten. Sorry Sam, but
I never understood why an average should be done. For CCD it's a sum, not average.
And even if CMOS binning can't be done directly as for a CCD, for me the sum
is the best choice. I do planetary and lunar imaging. Never used binning for
this kind of target and I don't know any person using binning for this kind
of target. But binning is cool for DSO imaging and in this case frame rate is
not a problem. And for short exposure imaging, a sum is an obvious choice.

Maybe a solution (if it's possible ?) could be to ask to the programmers of
Firecapture and SharpCap to add the possibility between sum and average. So
that everybody could choose.

Always sum for me !

Albéric


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 Post Posted: Sat Oct 07, 2017 12:05 pm 
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average and sum is the same
for bin2
average=sum/4
so you just need to *4 to get sum back
turn up gain just works as *4

and I think it's useless to choose RAW16 format under high gain

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 Post Posted: Sat Oct 07, 2017 3:02 pm 
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Sam,

No, that is not correct. Using high gain is not the same as binning for a number of reasons.

The most important one and one that is quite easy to demonstrate is that using very high gain causes significant quantization losses and loss of dynamic range not to mention blow outs, posterization and clipping due to the limitations of the ADC. It severely limits the kind of objects you can image and also exposure time.

I have experienced significant quantization losses even with 200-300 gain and relatively short exposures. Even star color completely disappears. I would definitely not want to push it higher.

Gain is not the right tool to achieve what you are suggesting. It like trying to use a hammer when you need a screwdriver. It completely destroys the image.

I also don't agree with your assertion that it is useless to choose RAW16 under high gain. This really depends on the gain applied and exposure time. Further if you x2 bin and use RAW8 you are guaranteed to lose dynamic range and suffer losses similar to quantization losses.

Ultimately you need to let the users decide what trade-offs they want to make depending on what kind of imaging they are doing. It is not appropriate for you to make these decisions for the user and also introduce these non standard operations which cause confusion.

Hiten


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