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This was my biggest challeng: to process the 3 bracketed image sets that captured the corona of the sun. The corona has a very high dynamic range. My first tries to use any HRD algorithms (in Lightroom, Nik HDR Efex...) did not go very far.
I found a couple of useful tutorials on the web:
- Solar Eclipse Composite Photography (Mr. Eclipse)
- Stacking Solar Eclipse Photos with Fitsworks (Hartwig Lüthen), and
- Extending the Dynamic Range by Compositing Multiple Solar Eclipse Exposures (Jerry Lodrigues)
They all employ a similar workflow:
- Align all images precisely
- Create a composite image of the sum of all individual images
- Run a radial blur filter or a Larsen-Sekanina filter of the composite. This will create an image with all the detail but low contrast (mostly grey or black)
- Multiply the sum image with the detailed, low-contrast image
- Make final adjustments (stretch, curves...)
Fitswork has an interesting approach: pick two images, overlay by subtracting one from the other, this will make it easy to align them. It does work. ... but I found it too cumbersome. I was looking around for another solution and found the FFTRegistration (Fast-Fourier-Transformation) script in Pixinsight. This is often used to align comet images.
Enter a reference image, add all the images, I wanted to store the registered images, so I checked this and click "OK". ... takes a while and this was the result:
Enter a reference image, add all the images, I wanted to store the registered images, so I checked this and click "OK". ... takes a while and this was the result:
I took this image into FitsWorks and selected the Larsen-Sekanina Filter:
There are only two settings:
Rotation and Radius. The tutorial recommended to start with Radius=2.0 and Rotation=1.31. I chose those settings and got this result:
It has a lot of detail - and almost not other information (low contrast, wrong colors...)
But multiplying both images gives this result:
Doing a simple stretch:
And some curves, saturation and color adjustments:
And then some final tweeks in Lightroom (devignetting, cropping...)
There are only two settings:
Rotation and Radius. The tutorial recommended to start with Radius=2.0 and Rotation=1.31. I chose those settings and got this result:
It has a lot of detail - and almost not other information (low contrast, wrong colors...)
But multiplying both images gives this result:
Doing a simple stretch:
And some curves, saturation and color adjustments:
And then some final tweeks in Lightroom (devignetting, cropping...)
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