2008. november 23., vasárnap

Another surface halo from Finland

On a couple of days there have been ground halos in Juva. It was best seen on a sportsfield running track. I stacked 45 images in Photoshop. Photographed with 10-mm and cropsensor.

Text: Jari Piikki

16 megjegyzés:

  1. Piikki is the chief. He always finds these great snow surface halos with best backdrop. This photo is also in its own class in that it shows with utmost clarity both 22 and 46 halos on surface in a natural manner. You can't really tell it is a stacked photo where camera has been moved on every shot.

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  2. That photo is not in fact very far away what I saw, because I have two eyes. Both of them have their own halos and when I move all the time new dots of light come out. When I take only one photo, the camera has only one "eye" and it doesn't move.

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  3. Piikki, we are wondering what's the revolutionary technique you are using, because there seem to be no signs of stacking in the image?

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  4. I guess Piikki's techique is simply to wipe the scenery clean of stacking, leaving only the area having the halos stacked. The other pixel information comes from a single frame. Right?

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  5. Yes, you are right. I also change blending of the layers in Photoshop to Lighten (100%). Then the dots of light come out better. It works better when the originals are under exposured, nearly black (except the dots). I can do that in RAW-converter. Then some adjustments with Levels, Curves and Saturation. There in not very much colours in this photo but I got a better with even darker originals.

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  6. Praise and hallelujah to Piikki. I just tried on my snow surface display. A genius method you have deviced. Lighten is the mode. But what transparency you use if the weight of stacked pairs is no 50:50?

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  7. I too have used lighten mode in some displays. Sometimes it works, sometimes some other mode is better. It boils down to the intensity of the background (ground, sky, clouds, contrails...). Keeping the ground very dark works indeed well.

    But how do you align/center the images when there is no sun in the frame at all?

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  8. Marko: A 100% lighten layer on top of another layer chooses the brigtest pixel of the two layers as to the output (corresponds to maximum stacking instead of averaging).

    Jari: I stack handheld photos by using the Difference blending mode and nudging the layer around until the image is as dark as it can get (this corresponds to the point of best correlation between frames). If needed one can assign a Curves or Levels adjustment layer on top of the two, that way it's easier to see subtle changes in the black output. Delete the adjustment layer afterwards.

    When the frames are aligned, change the blending mode from difference to what fits your needs (normal 50%, lighten 100%..).

    Not sure however how well this can be applied to surface photos with discrete sparkles and no diffuce arcs. Try it out.

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  9. Usually it is easy to align the 22deg halo. It is visible on both images at the opacity of about 50 %. Then I erase the other parts except the halo (ground)of each layer.

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  10. Lauri, Jari, thanks guys! Good points.

    I'm hoping to catch some surface halo action this year as well. Piikki has set the bar very high. Excellent!

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  11. I'm learning so much from these recent discussions. It has even come to my mind now that at next year's Halo Meeting we should have a hands-on workshop on these techniques. Jari would like to talk about halo photography and post processing, anyway...

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  12. Yep, I'm working on the subject whenever I have the time. And yes, good discussions here lately!

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  13. Thanks, Lauri. So, that's why the surface halo parts nearest to the camera come out the best and the halo looks more like that observed with naked eye - which is quite opposite to the averaging method.

    Yes indeed, instructive comments here recently.

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  14. Lauri, I applied that difference method of yours for "no sun disk visible" photos stacking, and it works excellently!

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  15. Nice to hear that it's helpful.

    Another tip for aligning uncooperative handheld photos in need of rotation in addition to translation: Enter the Free transform mode (Ctrl+T) and rotate&move the top layer freely.

    Should the sun be visible in both frames, align the sun images on top of each other, enter free transform, drag the rotation reference point at the sun and rotate the top layer until the halo forms coincide.

    Of course the difference + adjustment layer tricks can be applied here too.

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