Monday, July 30, 2007

Giving better looks for the stacked images

There is no denying it - stacked and unsharp masked halo image can be rather ugly. Ground objects are blurred and horizon is coated with blue glow.

But the looks can be improved by taking the ground from single untreated frame. That's what is done in the upper right image. It is the same image as the upper left except for the ground.

Near the horizon the clouds from the single frame dominate the sky, but in this case it has no significace as the halos are anyway blurred at the horison. This technique works best with high sun displays where halos are far from ground objects.

The display was seen in Lahti on June 9. The upper image pair is stacked (using Registax) from 72 frames taken during 15 minutes. The lower is 60 frames /12 minutes stack. It shows lower 24 plate arc on the right and perhaps some 24 halo on the left. Jukka Ruoskanen also photographed the display some 40 kilometers from Lahti. Another example of the ground adding is here.


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