Archived posting to the Leica Users Group, 2001/02/01
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]I'll take a guess and say diffraction - light bending around edges. Each straight edge produces another "spike" of light, so the star has as many points as the iris has blades. It's always more pronounced the more you stop down. It happens to all the light rays coming into the lens, but of course the bright sources are what you notice. I guess this is why the greatest sharpness for all lenses typically doesn't occur at small apertures. For what it's worth, to my eye this is one instance where fewer iris blades actually make a nicer image. C. -----Original Message----- From: Austin Franklin [mailto:austin@darkroom.com] Sent: Thursday, February 01, 2001 9:36 AM To: leica-users@mejac.palo-alto.ca.us Subject: [Leica] star pattern in lights when stopped down... What is the optical phenomenon that causes the star patter that is equal to the number of aperture blades, seen when stopped down, in some lenses? ******************************************************* The information transmitted is intended only for the person or entity to which it is addressed and may contain confidential and/or privileged material. No confidentiality or privilege is waived or lost by any mistransmission. If you receive this message in error, please immediately delete it and all copies of it from your system, destroy any hard copies of it and notify the sender. You must not, directly or indirectly, use, retain, read, disclose, distribute, print, or copy any part of this message if you are not the intended recipient. Thank you.