Archived posting to the Leica Users Group, 2001/02/01

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Subject: [Leica] Star Patterns
From: "Robert Rose" <>
Date: Thu, 01 Feb 2001 14:02:46 -0800

I have a different view on the "star pattern" phenomena.  I have found it is related to the number of blades, but   not how you might think.  It is related to the intersection points; the discontinuity where the blades overlap.

I have the slides to show this from a study I did.

A lens, such as a Hektor, with lots of blades, will not exhibit this at apertures which form almost a perfect circle.

Stopped down, a lens is more likely to have such sharp discontinuities between blades.  It is also necessary that the light be sharply in focus.  At stopped down apertures, it is more likely that the light source is in sharp focus.

One lens, the 35-70 f/4, will exhibit this at wide open aperture.  Examining the blades shows that the discontinuities appear on that lens when wide open.

By the way, a poor quality lens will not exhibit this star pattern.  It is a signature of quality.  Flare in a lens will also mask the effect.

Robert Rose