Hi All,
I have recently purchased an ASI1600MM pro. I'm trying to figure out calibration.
In the camera image controls section, does anyone know what "brightness" is, or how one is supposed to use it? Are any changes it applies added to the saved image ADU pixel values?
Is there a default? I"ve messed with it and it is currently at 100. Not sure where it started out.
thanks,
Steve
What is "brightness" ??
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Re: What is "brightness" ??
Hi Steve,
Brightness (called offset or black level on some camera brands) just adds a constant to the value of each pixel in the image – if you adjust this while you're showing the histogram you will notice that the histogram moves left or right as you adjust the brightness without changing shape (except if it hits either end).
Usually the best way to adjust the brightness is to do it once you have set other parameters like exposure and gain – once those are correct then show the histogram, cover the camera so you are taking dark frames and then adjust the brightness so that the main peak of the histogram is just separated from the left-hand side. This ensures that you're not getting any pixels (or at least not a significant number) that are being clipped to a level of zero. Failing to do this may mean that dark subtraction doesn't work as well as it should.
Cheers, Robin
Brightness (called offset or black level on some camera brands) just adds a constant to the value of each pixel in the image – if you adjust this while you're showing the histogram you will notice that the histogram moves left or right as you adjust the brightness without changing shape (except if it hits either end).
Usually the best way to adjust the brightness is to do it once you have set other parameters like exposure and gain – once those are correct then show the histogram, cover the camera so you are taking dark frames and then adjust the brightness so that the main peak of the histogram is just separated from the left-hand side. This ensures that you're not getting any pixels (or at least not a significant number) that are being clipped to a level of zero. Failing to do this may mean that dark subtraction doesn't work as well as it should.
Cheers, Robin
Re: What is "brightness" ??
Does using the Brain function to measure sky brightness automatically adjust the brightness level?
Re: What is "brightness" ??
Robin,
Thanks. I'm very familiar with offset from electronics. But I am surprised that with Brightness at 100 with the ASI1600, my histograms are still way over on the left until I lengthen exposures and/or gain. Looks like brightness is a fairly mild adjustment. Now that I know brightness = offset I'll play with it - clearly I should NOT be leaving it at 100! Likely throwing the calculations off in smart histogram.
best,
Steve
Thanks. I'm very familiar with offset from electronics. But I am surprised that with Brightness at 100 with the ASI1600, my histograms are still way over on the left until I lengthen exposures and/or gain. Looks like brightness is a fairly mild adjustment. Now that I know brightness = offset I'll play with it - clearly I should NOT be leaving it at 100! Likely throwing the calculations off in smart histogram.
best,
Steve
Re: What is "brightness" ??
Ah, good to know this. It explains why I get "weird" captures since I thought it was just a cosmetic thing and didn't influence the captures. Bit like adjusting the lightness of your monitor.