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Measured gain of SPC900NC


themos
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Hello, having nothing better to do I did some measurements of the SPC900NC webcam. I used SharpCap for capture and MaximDL for measurements. Here are the settings as saved by SharpCap


[Philips SPC 900NC PC Camera (LX Mode)]
Resolution=640x480
Frame Rate (fps)=5.00
Colour Space / Compression=YUY2
Exposure (s)=0.3
Output Format=Fits files (*.fits)
Brightness=64
Contrast=32
Saturation=0
Gamma=0
ColorEnable=255
BacklightCompensation=0
Gain=32

I tried gain=32 and gain=63. The FITS files saved registered a maximum value of 32640 which is 128*256 so I am guessing that the 8-bit values from the camera are somehow multiplied by 128 by the time they end up in a FITS file.

I tried gain settings of "32" and "63" (the maximum). The measured gain was 0.02 e-/ADU at "63" and 0.045 e-/ADU at "32". That's FITS ADUs that go from 0 to 32640. In terms of 0-255 ADUs the numbers are 2.6 and 5.8, respectively.

As far as read noise is concerned, I measured 21.6 electrons at "63" (which doesn't make much sense to me). At the "32" setting, I just couldn't get any variation in the bias frames, presumably because of quantisation error. I think that means that the read error is less than 5.8 electrons.

Let me know if you've measured these yourself.

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