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About Zerene masks

 
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soldevilla



Joined: 16 Dec 2010
Posts: 551
Location: Barcelona, more or less

PostPosted: Sat Aug 08, 2015 12:20 pm    Post subject: About Zerene masks Reply with quote

I'll try to explain me. I'm thinking about the influence of the number of images stacked in the quality of the final image. I do not know (and this is my question) if the masks that produces Zerene on the areas focused of each individual image are blurred, and in what proportion.

This seems important to me, because in the final image each image fragment will be the result of several combined images, increasing the signal to noise ratio and thus the end definition. This is the basic method we use when we take pictures of planets with the telescope, but with thousands of individual images.

Are the edges of the masks that produces Zerene blurred? If so, the number of individual images not only needs to be enough to not produce banding but the more images we use, better will be the result.

When I change my old iMac, I can try this Very Happy
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rjlittlefield
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Joined: 01 Aug 2006
Posts: 20022
Location: Richland, Washington State, USA

PostPosted: Sun Aug 09, 2015 3:25 pm    Post subject: Re: About Zerene masks Reply with quote

soldevilla wrote:
This is the basic method we use when we take pictures of planets with the telescope, but with thousands of individual images.

Sure, but there is a fundamental difference between astro stacking and focus stacking.

In astro stacking most or all of the source pixels are good, and you're looking to combine them in such a way as to make the final image even better. Averaging improves the signal-to-noise ratio.

In focus stacking most of the source pixels are bad (out of focus), and you're looking to pick out the few good ones so that you can make a useful composite. The only places where it makes sense to do any sort of averaging is in places that are out of focus in all frames, and in the overlap regions where two adjacent source frames are more or less equally out of focus.

In Zerene Stacker, there are two fundamentally different stacking methods.

PMax doesn't use anything that you would recognize as a mask, so your question cannot be answered. PMax also typically increases noise, because it cannot always discriminate between pixel noise and real detail, in deciding what to preserve.

DMap does use something that looks like masks. In that case the answer is that the edges are blurred by typically a few pixels, in areas that contain enough detail for the software to accurately determine focus. In areas that do not contain that much detail ("black in preview" while adjusting the contrast threshold slider), the blur can be indefinitely wide depending on how the depth map gets interpolated. But in no case will DMap do a weighted average of more than 2 frames.

--Rik
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soldevilla



Joined: 16 Dec 2010
Posts: 551
Location: Barcelona, more or less

PostPosted: Sun Aug 09, 2015 3:33 pm    Post subject: Reply with quote

OK, Rik, many thanks! If I understand you, no make sense to do an extra number of images. Less work, better. Very Happy
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