To bright picture - Gamma and Brightness at "bottom"

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Bhlm.Astro
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To bright picture - Gamma and Brightness at "bottom"

Post by Bhlm.Astro » Sat Jun 03, 2017 1:00 pm

Both myself and a mate have issues with the new versions of SharpCap, he with v2.9 and I both with 2.0 and 3.0.

My mate is using a Celestron webcam, I use a modified Trust webcam.

When connecting the cams on respective PC, the gamma open up in the leftmost position. And with the intended planet strongly overexposed. For instans, Jupiter is just a big bright blob, not possible to reduce to see the bands. When we both used v2.1 it worked fine.

Cheers
Lars M
"Borgholm Observatory"
Gaf.homeip.net

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admin
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Re: To bright picture - Gamma and Brightness at "bottom"

Post by admin » Sat Jun 03, 2017 6:13 pm

Hi,

I don't have a celestron webcam, but I do have a Trust one - I have just tested that with 3.0 (on Win10) and I can adjust Exposure, Gain and Gamma correctly to get a correctly exposed image for different lighting intensities.

Do some or all of the exposure/gain/gamma controls not work for you?

cheers,

Robin

Bhlm.Astro
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Joined: Sat Jun 03, 2017 12:46 pm

Re: To bright picture - Gamma and Brightness at "bottom"

Post by Bhlm.Astro » Sun Jun 04, 2017 11:37 am

Hi,

we solved the issue with the Celestron yesterday evening. I unchecked the automatic exposure and suddenly we had better range to adjust with. When we took it down to 0.6ms it worked.

My guess is that the AE is on in my Thrust cam as well, but I cannot find how to unchecked it and manually set exposure time.

I can adjust all the exposures controls, but even when set in minimum the light from example Jupiter is to bright, just like a bright flashlight, all details washed out. Even if setting Image controls Gain, Gamma and Brightness as well as filter->Enhancement Video-> Light (Gain?) and Gamma to bottom settings. Cant find any AE control.

Cheers

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Re: To bright picture - Gamma and Brightness at "bottom"

Post by admin » Sun Jun 04, 2017 4:24 pm

Good to hear that you are making some progress with the Celestron camera.

With the Trust camera, if you have an exposure control and the 'auto' checkbox is unchecked then you are using manual exposure (see http://docs.sharpcap.co.uk/2.9/#!3!Camera%20Controls). However many webcams are designed for consumers and try to be 'smart' by auto adjusting other settings. This can be a problem for astro photography when their smart auto settings don't work at all well.

If the auto checkbox on the exposure control is not enabled then that means that there is no auto exposure made available by your webcam driver. If your webcam only supports auto exposure (some are like this) then you don't see an exposure control at all I think.

cheers,

Robin

Bhlm.Astro
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Re: To bright picture - Gamma and Brightness at "bottom"

Post by Bhlm.Astro » Mon Jun 05, 2017 3:09 pm

Thanks,

Means that this trust webcam is a dud for astro imaging, since the option of choosing AE isn't there. Means I have to find another webcam.

Cheers

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Re: To bright picture - Gamma and Brightness at "bottom"

Post by admin » Mon Jun 05, 2017 9:44 pm

Normally people want manual exposure rather than auto exposure for astro-imaging, but if the manual exposure isn't giving you the range of exposures you need with this camera then you do have a problem.

For webcams, SharpCap doesn't only brings the controls and ranges that the camera itself offers into the UI - I don't lock down exposure ranges or presence/absence of controls - SharpCap asks the camera what it is capable of and presents UI that makes that functionality available. In fact, for a camera like the Trust one, it's likely that the camera works using 'USB Video Class' which means that the driver is also a generic driver and is pretty dumb too - the answers to questions like 'what exposure range' and 'is auto exposure available' come directly from the camera hardware.

cheers,

Robin

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