Author Topic: Bayer drizzle instead of de-Bayering with OSC  (Read 356 times)

Offline ChrisFC

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Bayer drizzle instead of de-Bayering with OSC
« on: 2019 April 01 16:08:29 »
This has got me completely stumped

I'm using an OSC, asi071, and dithering. When processing I follow a standard process of calibration, cosmetic correction, debayer, blink, subframe selection, register, local normalisation then integrate, drizzle integrate. It works great and increases resolution on images with my refractor which is working at 1.8arcsec/pixel.

I've heard of Bayer drizzling. But for the life of me I can't figure out where it is in the processing workflow.

Offline 1DegreeN

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Re: Bayer drizzle instead of de-Bayering with OSC
« Reply #1 on: 2019 April 01 18:35:32 »
If you are ticking the "Enable CFA Drizzle" box on the Drizzle Integration process then you are already doing Bayer drizzle. In previous versions of PI it was more of a palaver to do Bayer drizzle but the process has been streamlined now.

Offline Juan Conejero

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Re: Bayer drizzle instead of de-Bayering with OSC
« Reply #2 on: 2019 April 02 01:57:00 »
As 1DegreeN points out, CFA drizzle[1] is completely integrated in the preprocessing workflow in current versions of PixInsight, from calibration to integration.

To be more precise, if you want to achieve the best possible result starting with mosaiced raw data (be it DSLR or OSC raw data), and the amount of data available is not marginal, then CFA drizzle is not optional. You must perform it always. The Debayer tool only serves as a previous step for image registration (StarAlignment) and weighing / outlier rejection (ImageIntegration), but de-Bayered frames are just temporary working images. If your data justifies it (both because it is subsampled and because you have enough frames), you can perform drizzle with a scale of 2. Otherwise select a scale of 1 to perform a 'regular' CFA drizzle.

And to be even more precise, in many cases, if not in most of them, drizzle integration is the best option also for non-mosaiced data, that is, for monochrome CCD/CMOS raw data. DrizzleIntegration with a scale of 1 may achieve better results than ImageIntegration because drizzle does not apply pixel interpolation. The final SNR improvement is normally smaller with drizzle, but the total absence of interpolation aliasing artifacts is a wonderful compensation. When there is enough data, I would consider using drizzle x1 on a regular basis. Food for thought :)

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[1] AKA Bayer drizzle, although this term is incorrect strictly, since you can perform drizzle to fill the holes of any CFA pattern, such as X-Trans for example, which PixInsight fully supports.
Juan Conejero
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Offline ChrisFC

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Re: Bayer drizzle instead of de-Bayering with OSC
« Reply #3 on: 2019 April 02 03:05:04 »
Thanks for the really helpful explanations of how it works. I didn't realise the debayered images were temporary working files.

I'll also try the regular CFA drizzle. I'm using one of the STC duo narrowband filters (Ha & OIII) on my OSC, so hoping this will help with resolution. We shall see what we shall see!

Offline Juan Conejero

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Re: Bayer drizzle instead of de-Bayering with OSC
« Reply #4 on: 2019 April 02 03:39:12 »
Quote
I didn't realise the debayered images were temporary working files.

They are temporary only if you decide to use drizzle to generate your integrated image, which is the best option for CFA data, in my opinion. Others may have different points of view about this. My advice is to compare both results, after ImageIntegration and DrizzleIntegration, to make your own decisions.
Juan Conejero
PixInsight Development Team
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