Can't get rid of offset

[dkoschny]

Hi, I am new to SharpCap. Have played with it a bit using it with my QHY178 GPS. It is the only tool which gives me the full speed performance. BUT: After some initial grabbing I must have set something wrongly - I always have an offset of about half way to maximum brightness in my images, making the background very bright and contrast bad. I checked the 'offset' but it is at 0. So all good. What else could be wrong?

I checked the camera with FireCapture, there the image is great, with black background. So its not the camera (but there I don't get the frame rate - so I do prefer SharpCap

I went through the user manual, I did search the FAQs, but couldn't find anything.

I am sure this is something silly, but I would appreciate any help.

tx Detlef

[admin]

Hi,

can you share a screenshot showing the image displayed along with the histogram and the major camera controls - there will probably be something obvious as you say, but it's going to be easiest to spot that from a screenshot. I do wonder if you have used the display histogram stretch to brighten the mid tones and shadows and forgotten to cancel it (https://docs.sharpcap.co.uk/3.2/#!2!Min ... %20Stretch)

cheers,

Robin

[dkoschny]

Ok I have checked this.I played with the histogram controls but it didn't change the offset. Also, the user manual says it only affects the display, not the recordings. But I see the same bright background in the recorded videos. Then I read further in the user manual and checked that the 'offset' for the QHY camera was set to 0. I changed it and noted something interesting - there seem to be pixel values at 0. But, as I said, using FireCapture shows me a fine image.

I attach some screenshots - the light image (..._x.png) is a bush in my garden, the other one (..._with_offset.png) is a dark image (just covering the lens). I can do some night time images later today.

dvk

[admin]

Hi,

Ah, I think I know the cause of this one. Qhy cameras have a gamma control and for some reason the value of that control can jump to zero occasionally (note this is without any software like SharpCap actually asking to set the value to that). If you have a gamma of zero then you get a totally white image which was the way the bug first appeared. Now SharpCap forces the gamma to at least 0.1, which leads to the sort of washed out images you are seeing.

If you expand the 'Image Controls' section on the right see the gamma slider – put that to 1.0 and your images should be back to normal.

Cheers, Robin

[dkoschny]

Robin, you are great. That fixed it! Thanks so much. I just heard again today in a presentation that I should be using SharpCap and SharpCap only Now I will.

dvk

[admin]

Thanks for confirming that worked for you. I wonder if I should set the gamma back to a default 1.0 if I find it at a bad value to automatically cure this problem in future?

cheers,

Robin