Poor contrast and color in sharpcap vs ASI Studio

[eschmitt]

New Sharpcap user here, purchased to support livestacking over zoom/streaming for virtual events. I wasn't able to trial because the memory cap didn't get along with the ASI6200.

I'm fairly familiar with image processing and stretching, (I process in pixinsight) but after a couple of nights of experimenting I cannot seem to get images to look decent in sharpcap. The manual/tutorials seem pretty straightforward, but the results I'm getting aren't great. I'm hoping its user error.

Whats frustrating is that I load up ZWO's livestacking program and it displays far better looking results after even a single image and 5 seconds of moving sliders. So, my question is what knobs do I have to turn in sharpcap to move my results closer to what I'm seeing in ZWO's free program so that I can then learn to use sharpcap's greater functionality to improve from there.

Sharpcap's auto stretch seems to always overstretch, even when turned down to minimum in settings. The auto color balance also always replaces a strong green cast with way too much blue. After manually tinkering, I still can't get the color to look quite right using either Raw16 and then debayer or RGB24. It looks like ZWO is using some sort of native debayer that does a much better job with this camera. Is there anything in sharpcap I can tweak to help emulate ZWO's debayer math?

Secondly and more importantly, I cannot get rid of the bright background in sharpcap without moving the black point way too far up which destroys half of the image or moving the midpoint so much that the target is lost trying to calm the background. Does anyone know what ZWO's "contrast" slider does and why it seems to do such a good job at this? Any advice on how to calm the background in sharpcap?

Equipment in use here: C14 Edge HD w/ ZWO ASI6200 OSC on the hyperstar. No filters. 30 second exposures.

Examples: Yes I know the seeing is awful and its out of focus, sharpcap's focus assistant also doesn't seem to work on this setup and I was using a night of poor seeing to experiment and got tired of switching back and forth to Theskyx to run @focus3.

sharpcap screen.PNG (499.48 KiB) Viewed 1690 times

^ Sharpcap with auto on the histogram set and neutral color balance

sharpcapcolor.PNG (540.45 KiB) Viewed 1690 times

^ Auto color balance going crazy

zwo screen.PNG (664.55 KiB) Viewed 1690 times

^ ZWO's livestacker with just an auto stretch. Note the color balance.

zwo contrast.PNG (756 KiB) Viewed 1690 times

^ Increasing saturation and most importantly, the contrast slider. The contrast slider has a huge effect. I've over applied it here to exaggerate the effect for clarity. How do I achieve this background darkening effect in sharpcap?

[admin]

Hi,

when you adjust the black level line in SharpCap, it automatically moves the mid level by the same amount too - often this is useful, but it could be causing the problems that you are seeing with the object fading out when you darken the background. The fix for this is to adjust the black level first to get the background dark enough and then to set the mid level line further to the left to brighten up the target again.

If you want to share the stack (saved in 32 bit format) then we can test the auto stretch / auto colour balance on it to see if anything can be improved.

thanks,

Robin

[eschmitt]

Thanks for the reply.

I spent a fair bit of time adjusting both the black and mid levels in Sharpcap's histogram to little avail. I had already messed with what you suggested, I found myself moving the black point well into good data and clipping far too much to calm the background enough. If I then pushed the mids harder to brighten the object it resulted in an ugly, barely recognizable and detail-less mess.

I'm familiar with histogram stretches in pixinsight and other software where adjusting the black point also shifts the mids. Even single uncalibrated subs will look pretty decent after a quick stretch. This bright background and color issue is only showing up in Sharpcap.

I did not save the sharpcap stacks from my nights of experimenting but I will next time around.

I don't see any obvious way to load existing images into sharpcap, is that possible or can it only grab from a camera? Seems like it might be useful to experiment with loading known good images into sharpcap to see how it displays them.

[BlackWikkett]

Hi eschmitt

You can load images for stacking from the camera menu choose "Folder Monitor Camera." Once open in the camera control panel on the right side under camera controls select "Browse" next to source folder. Navigate to a folder that contains the files you want to stack. Then start live stacking as normal. The play button is process all frames and will stack all or you can step through them one at a time. This works best with raw frames

https://docs.sharpcap.co.uk/3.2/#Virtual%20Cameras

Good luck, Chris