Pedestal added?


#1

Does the Sequencer adds a pedestal to the image data?
Thanks
Renan


#2

SGPro does not alter the image data from cameras in any way. We just save it as-is straight to the disk and move on.


#3

What actually is a ‘pedestal’ added to an image ?

:confused:


#4

A pedestal is a fixed value / amount (like 100) that is added to or subtracted from every pixel in an image. Some image processing software can automatically subtract a fixed amount from every pixel’s value as a way to eliminate some of the background signal in an image.

Charlie


#5

HMMmmmm Interesting !

I’m glad SGP does not do stuff like that. On the Pixinsight forum there are Pedestal’s galore

So would this “eliminate some of the background signal in an image”, would this be in an attempt
to lessen the background noise for instance ?


#6

it’s related to calibration and is only tangentally related to background signal. if for some reason your bias subtraction leaves your calibrated darks with values that are less than 0, then you can add a pedestal to the master bias frame to ensure that the result of the bias subtraction is always positive. later on down the calibration pipeline, the pedestal is subtracted. at that point the values in the light frame being calibrated are usually large enough (because of the sky background) that subtracting the pedestal leaves the calibrated light with non-zero values in every pixel.


#7

Thanks pfile,

I assume a negative value would leave you with a 100% black pixel then with no way of regaining the data that used to be there ?

Regards
Paul


#8

yeah that’s the idea, the data would be accidentally destroyed without the pedestal addition/subtraction process. it’s not really a common problem, i have seen it once and i think it may have been due to different gain settings in the bias and dark. i guess it’s also relevant if you’re trying to calibrate your bias (with an overscan region) but that’s also a pretty rare thing.


#9

pfile,

I am Enlightened Thank You !

:grinning:


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