Flats problem

[Tommohawk]

Hi all. I've been having some big problems with my flats - long story short: it appears that flats captured using the flats tool look very different to flats taken just as though they were lights. I think the reason is that I had the box ticked which "applies new flat when capture complete". So if I take flats using the tool , and then take flats as though they were lights ( I did this for test purposes) it seems those will have the flats applied and therefore wont work for calibration.

Does ticking this apply the flat to subsequent lights? Or just to the image on the screen? And if it does apply them, does it continue to do so after a restart?

Hope that makes sense.
Thanks Tom

[admin]

Hi,

if you have enabled the dark subtraction or flat correction options in SharpCap (which is what happens after capturing a flat if you have the 'apply new flat when capture complete' option checked) then the adjustments apply to both the screen view and any saved files (see https://docs.sharpcap.co.uk/3.2/#!2!Pre-processing)

This means that if you try to capture flats for another tool after turning on flat correction in SharpCap then you will not be in a happy place - the files you save will be truly flat (no variation) and will not correct anything.

Using SharpCap's built in flat correction is an alternative to using flats in post-processing. I'd suggest not trying to use both.

cheers, Robin

[Tommohawk]

Hi Robin, thanks for clarifying. To be fair the flat capture tool info does pretty much make clear that if that box it ticked, the flat will be applied to any subsequent lights captured.

BUT I'm still not clear whether this will be retained on a subsequent restart of SharpCap. If that box is ticked, is the flat "held" in the memory and applied to lights captured in any subsequent session??

Regards
TOm

[admin]

Hi Tom,

Whether the flat will be retained the next time you start SharpCap depends on the choices you've made in the SharpCap settings window – there is an option there to automatically remember the camera settings and restore them each time – if you have that option ticked then the flat correction will be restored along with all the other settings. If you un-tick that option then then a restart of SharpCap will clear the flat correction control settings.

Hope this helps, Robin

[Tommohawk]

Hi Robin

Well Ive spent some time looking for this setting and cant see it anywhere! Can you explain where this is please?

Also I notice that if I untick the "apply new flat when capture complete" box in flat capture tool, this setting isn't retained. So when I open SC again, the box is ticked again by default. Did you mean this to be so??

Regards
Tom

[turfpit]

Tom

File > SharpCap Settings > General tab

settings.JPG (35.8 KiB) Viewed 2259 times

Dave

[Tommohawk]

Hi Dave

OK thanks for that. However, call me Mr Thicky but I don't understand what that means! I'm really not trying to be difficult or pedantic but does this mean restore the setting to those last used or restore them to the default?

Regards
Tom

[Tommohawk]

I've had a play with the settings, and what seems to happen is with that box ticked, upon restart the setting last used are applied ie the same gain and exposure etc, even without loading a capture profile, and the flat is also loaded as you say.

However, if a capture profile is loaded (either the same or any other profile) the flat is then removed.

So I can now see how it works, and to be fair I think its caught me out because I've been doing some odd routines, ie capturing flats using the special tool - which works well - followed by capturing "lights", which I wouldn't normally do.

Anyhow, leaving that aside, Robin can I ask a request, and throw in an idea please?

1. I don't think its a good idea that the tick box in the flat capture routine marked "apply new flat when capture completes" keeps reticking on startup. To my mind, if this is unticked by the user it should stay unticked, no?

2. Because its normal practice to use dark flats, it might be helpful to have a routine for this too, or at least have the file or folder name for the light flats include the exposure time and gain, so that when doing dark flats you know what exposure to match them to - does that make sense?

thanks, Tom

[turfpit]

Tom

Yes you have that now. Also be aware that holding down the <CONTROL> key when connecting a camera in SharpCap will not reload previous camera settings. See https://docs.sharpcap.co.uk/3.2/#General%20Tab

Dave