L0 = L1 + D

Features suggestions that are not currently planned for inclusion will be moved here. In general features moved here are very unlikely to be added to SharpCap, perhaps because other programs already have this functionality or that the functionality could be achieved using SharpCap scripting.
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oopfan
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L0 = L1 + D

Post by oopfan » Thu Aug 03, 2017 11:23 pm

Robin,

I made a major blunder by reusing darks that were acquired the previous night at a cooler sensor temperature. The result is that my newly acquired lights, with dark frame subtraction turned on, have lots of hot pixels shining through.

Is there a way to get SC to perform the inverse of dark frame subtraction so that I can salvage 90 minutes of work?

Thanks,
Brian

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Re: L0 = L1 + D

Post by admin » Fri Aug 04, 2017 8:19 am

Hi Brian,

SharpCap can't do this, but various other software like IRIS (free, very complex but powerful) and PixInsight ($$$, also very complex but powerful!) can. You may find that there is a problem with recreating the original frames as the saved frame will be clipped to have a minimum of zero even if the dark subtraction would have led to a negative value - ie dark subtraction in SharpCap is

result = max(255, min(0, light - dark)) [ or 65535 not 255 for 16 bit depth]

cheers,

Robin

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Re: L0 = L1 + D

Post by admin » Fri Aug 04, 2017 8:21 am

Just for the record, SharpCap preserves -ve pixel values that come from dark subtraction during the live stacking process (as that makes dark subtraction more effective). However, even when live stacking negative pixel values are clipped when saving the stack.

cheers,

Robin

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