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Re: [OM] Flare redux: Sun Stars?

Subject: Re: [OM] Flare redux: Sun Stars?
From: Thomas Bryhn <thomas.bryhn@xxxxxxxxxx>
Date: Sat, 08 Dec 2001 16:25:35 +0100
At 23:42 07.12.01, Joel Wilcox wrote:
So I guess these are my questions:

1. Is this kind of sun star a type of flare?

No. Flare is reflections inside a lens (or camera), the star effect is diffraction. In this case you obviously used a lens with 8 aperture blades, and the uneven diameter of your lens opening creates spikes like this. If your aperture was perfectly round there would also be diffraction, but it would be spread out evenly around the sun.

2. What effect might the lens coating have on the creation of sun stars?

None.

3. Does the position of the sun in the sky affect their size? (The Thumb shot
was made mid-day whereas the Lake of the Clouds shot is at dawn.)

No. Neither does it help produce diffraction to hide parts of the sun behind another object, but you need the contrast of the dark foreground to see the diffraction spikes. Your first picture is a perfect example of this, and if your film had much, much higher dynamic range it would also be possible to see the spikes in the upper part of the image.

Regards,
Thomas Bryhn


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