Dark and flat: checking live results during live stacking

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ippiu
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Joined: Fri Jul 06, 2018 7:02 pm

Dark and flat: checking live results during live stacking

Post by ippiu » Tue Mar 12, 2019 1:16 pm

Hi.
Because i'm having some problems about good results with dark and flat calibration during live stacking, i was thinking about a possible error i did during my last test.
While i was looking for a solution, i came accross this Robin's sentence "Once you have chosen your dark file it will be subtracted from each frame captured from then on (unless you set the subtract dark dropdown back to 'none')".
So, i explain my test.
I start live stacking. After some frames i add the dark frame: i wait one frame to see the live result. Then, i switched to "none" and wait one frame. Then i add the dark twice, to see the live result another time...And so on with flats, adding and remove them while the live stacking was going on...
So maybe that this cause the problems of poor results in dark and flats calibration during stacking? Changing continuously between adding dark and flat calibration to live stacking (and removing them, set back to 'none') could cause an error?

So if you start a live stacking session with dark calibration, for example, do you have to keep it unchanged? No possibility to add and remove flat or dark during live stacking session?

Thanks

Andrea

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Re: Dark and flat: checking live results during live stacking

Post by admin » Tue Mar 12, 2019 10:20 pm

Hi,

It's certainly not good practice to switch either dark or flat correction on or off during live stacking. If you stacked 10 frames with the dark correction turned on for 5 of them and turned off for the other 5 then you would get a final image that effectively only had half of the effect of the dark correction included in it. That is, for instance, if you are using dark correction to try to remove amp glow then the amp glow would still be present but not as strong as if you had used no dark correction for any of the frames.

While it's okay to do this sort of thing while testing or playing around, for serious stacks where you intend to use the final image you must have the dark and flat frame selected for all frames going into the stack.

Cheers, Robin

ippiu
Posts: 21
Joined: Fri Jul 06, 2018 7:02 pm

Re: Dark and flat: checking live results during live stacking

Post by ippiu » Wed Mar 13, 2019 8:03 am

Thanks, Robin.
I thought that dark or flat correction is applied to final stacked image and not to every single frame.
So when i will do the next test, i start a live stacking with some settings (dark and flat on) and leave it unchanged until final stacked image has been saved. Then i restart a new session with other settings (for example, dark and flat off) and save the final image, and so on..., to get all combinations of stacking images.

Cheers

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