Histogram settings

Discussion of using SharpCap for Deep Sky Imaging
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Moonstruck
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Joined: Tue Aug 17, 2021 4:34 pm

Histogram settings

#1

Post by Moonstruck »

Just a general question on the histogram. When I am imaging, with the gain and exposure set to a fixed number (say, gain at 120 and exposure at 60), does changing the histogram settings affect the actual image that is captured? Or is the histogram simply a visual aid, that can be changed while imaging, and does not affect the actual image capture?
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admin
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Re: Histogram settings

#2

Post by admin »

Hi,

the answer is... it depends :)

If you are using the small histogram on the right hand side (this one : https://docs.sharpcap.co.uk/4.0/#Mini%2 ... %20Stretch) then the adjustments only affect the display, not the saved image. With the one exception - if you use the save button on that histogram, it will save the image exactly as shown on screen - ie including the adjustments.

If you are using the adjustments in the live stacking histogram, then you need to check out the info about the 4 different types of live stack save - see https://docs.sharpcap.co.uk/4.0/#Actions%20Group . The last two in the list are affected by the live stack histogram (and colour) adjustments. The last one is also affected by the mini histogram adjustments.

Hope this helps,

Robin
Moonstruck
Posts: 56
Joined: Tue Aug 17, 2021 4:34 pm

Re: Histogram settings

#3

Post by Moonstruck »

Thanks. The only thing I have been using the histogram thus far is to stretch the image so I can get a better look at it. It is good to know I can change it as desired (without hitting save) without affecting the image.

Which brings me to another histogram question. Can the small histogram be used to let me know how to set optimal gain and exposure? I know there is a smart histogram feature which I haven’t set up, but that takes some time to figure out... can I use the small histogram for a general gauge on what I should use for gain and exposure, without using the smart histogram?

I typically just set the gain to 120 for all my imaging (no matter what exposure I choose) but I am sure I should be doing some sort of calculation to decide on the best gain setting. I have never mastered the gain vs. exposure settings, and not sure how to go about this. Thanks.
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admin
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Re: Histogram settings

#4

Post by admin »

Hi,

you can't really do any detailed work on the correct gain/exposure using the small histogram, aside from the very basic step of trying to make sure the main peak is separated from the left hand side and isn't more than about 25% of the way accross. Unfortunately that's *not* sufficient to ensure a good gain/exposure combination, so you are best using the main histogram and the smart histogram functionality.

cheers,

Robin
Moonstruck
Posts: 56
Joined: Tue Aug 17, 2021 4:34 pm

Re: Histogram settings

#5

Post by Moonstruck »

Ok, thanks again.
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