SharpCap Forums

Hello,

I’m someone who usually never touches those "awesome new features" (which rarely work right and mess up the image)... but I don't know what got into me: I clicked on "Colour calibration" with my 2600C... I found it complicated to use and couldn't see any benefit, so I tried to exit that mode, but... surprise: it was impossible!!!! Ever since I messed with that, the histogram has been acting weird—it doesn't respond the same way anymore—and if I switch from a clear filter to an Ha-OIII filter, for example, the image goes black. I have to go back into "Colour calibration" (which I don't want to use!) just to get an image back!!!

That was already a pain! But tonight, I set up my 2600M camera... the mono version... And guess what: no image at all!!!!! That blasted SC software is hell-bent on performing color calibration, I suppose, but since the function is disabled (it's a mono camera!), I can't run it, and my image stays black even when I adjust the histogram manually!!!! In short, SC is busted—completely unusable.

What possessed me to mess with that setting?? And how come nobody is reporting the huge problem this function creates?

So, I installed version 4.2... but no, the software retrieves the settings from somewhere, and I'm still stuck with a black screen because of that cursed "colour calibration"!!!...

Clear nights are rare, so I have to admit, this bug is incredibly frustrating!!

Where can I find the stored SC settings so I can delete the line telling it to always activate this function that's ruining everything? I couldn't find it in Appdata/Roaming... Does anyone have any ideas?

Many thanks to you all (and to our revered SC grandmaster: there's a major issue here that needs fixing for the next version

P.S.: I reverted to the June 23, 2025 version to stop SC from using "Colour calibration" (since it didn't exist back then!). Otherwise, that blasted hidden setting ruins the image, and there's nothing I can do about it. It really ought to be possible to disable that thing...
In the meantime, it's working again, albeit on an old version.

When live stacking in the settings tab make sure the lines for repeating color calibration and adjusting background are un checked. Then make sure the box on histogram page for tracking is un checked.

Hope this helps

Gfischer wrote: Wed Sep 23, 2026 9:46 pm When live stacking in the settings tab make sure the lines for repeating color calibration and adjusting background are un checked. Then make sure the box on histogram page for tracking is un checked.

Hope this helps

Thank you. I'm going to look into what those things actually are; I'm just a "basic" user—I stick to the standard functions and that suits me fine (EAA).

It would be easiest if you could just toggle it on or off with a button or checkbox... Right now, it stays active even when you don't want it to, simply because you used it once!!...

Anyway... I deleted everything, and now it's working well again with an old SC. I'm hoping the old version clears out the hidden settings from that "colour calibration" feature, so that when I reinstall a recent version, the setting won't be active anymore (and I'm never touching it again!! )

Hi,

OK, let me explain what does and doesn't happen when using colour calibration, as I think part of the problem is that it's not working the way you think it is and therefore it makes it seem very strange.

When you press the colour calibration button, it will adjust three things...

1) The colour balance sliders on the right of the histogram to try to account for the different sensitivities of the camera colour channels
2) The background subtraction amounts in the live stacking 'background subtraction' page to try to remove the sky background and any colour cast in the sky background
3) The stretch of the image (black/mid/grey levels)

If you want to undo those changes, the procedure is as follows

1) Reset the colour balance sliders using the 'Reset colour balance' button (an anticlockwise arrow under the blue/saturation sliders)
2) Turn off background subtraction in the 'Background' live stacking tab, or use the reset button there, or close and re-open SharpCap (the background adjustments deliberately are not saved through a restart)
3) Reset the live stacking histogram stretch levels on the histogram tab, or adjust them as you see fit, or use the auto adjust button

You can also use the nuclear approach - go to the 'Log' tab and press the 'Reset All Settings' button which should reset everything in live stacking back to defaults.

If you are using SharpCap 4.1, Colour Calibration only does something when you press the button - when you do, it will make the changes described above, but it will not continue making changes or do anything later just because you have pressed the button once (except that the changes have been made).

SharpCap 4.2 is a bit more complex - there is an option available to automatically colour calibrate after the first frame (or the first N frames) of the stack - this can be found in the far right settings tab. There is also a new option for 'stretch tracking' which tries to gradually adjust the stretch/background settings of your stack to cope with changes in conditions as the stack progresses. However, both of these are *off* by default.

There was a bug in some beta versions of 4.2 where the automatic colour calibration after the first frame could also happen with mono cameras, but that is resolved in the latest versions.

Given the description of how your histogram has gone weird and you are getting black images, my guess is that the colour calibration set up background subtraction to compensate for the background brightness/colour cast in your colour image, and that stayed active when switching to your mono camera. The steps given above to reset the background subtraction should resolve the issue.

cheers,

Robin

admin wrote: Thu Sep 24, 2026 1:36 pm my guess is that the colour calibration set up background subtraction to compensate for the background brightness/colour cast in your colour image, and that stayed active when switching to your mono camera.

Dear Robin,

First of all, thanks for the explanations. Several people suggested I reset the "background subtraction" setting, but since I hadn't touched it, I told them that it couldn't be the cause and I didn't bother checking... My mistake!!! I now realize the issue almost certainly stems from that function...


> my guess is that the colour calibration set up background subtraction to compensate for the background brightness/colour cast in your colour image

That’s exactly it, I think. Or at least, I’m hopeful
It’s overcast tonight, but as soon as I can, I’ll disable that background feature, and hopefully everything will go back to normal! (If not, I’ll try the "nuclear approach"

I had already considered using an older version of SC... but since I like keeping things up to date, I wasn't too keen on that.

Thanks again for the help and explanations—clear skies!