[LargeFormat] Keep the list alive! - Off Topic - 6x6cm

[Richard Knoppow]

-----Original Message-----
From: Jim Hemenway <Jim@Hemenway.com>
Sent: May 6, 2004 1:51 PM
To: largeformat@f32.net
Subject: [LargeFormat] Keep the list alive! - Off Topic  - 6x6cm

Hi Folks:

Some of you folks know a lot about optics, so I'm wondering if anyone 
can tell me if chromatic aberration is the name for the green and red 
stripes on the sides of the lighthouse in the first picture in the set 
below.  Look for the blow-up under the Boston Harbor photo on the left 
side of the pair.

If it is chromatic aberration, why does it show up one one fisheye lens 
and not the other?  Is there a missing element?

These are some side-by-side fisheye photos taken with the Arsat 30mm on 
a Kiev 60, and the Zeiss F-Distagon 30mm on a Rollei 6008i.

When you click on any of them you'll be presented with large photos. If 
you press your right mouse button, (in Netscape 7.1) and choose view 
image, the photo(s) will be reduced in size to fit your screen. I think 
that something similar is available in IE.

Astia 100

Most at f8 - f16

No sharpening

No PS work except for spotting.

http://www.hemenway.com/ArsatDistagon

Thanks,

Jim Hemenway


   I am assuming that you can see the same thing on the film. If so, its chromatic. 
    Chromatic aberration takes two forms: one is lateral, one longitudinal. Longitudinal is the kind most of us are familar with; its the reason a magnifying glass shows color fringes. The focal length of the lens varies with the color so different colors come to focus at different distances from the lens. Lateral color is also known as chromatic difference of magnification. Lateral color can exist in lenses which are corrected for longitudinal chromatic aberration. It produces images which all focus at the same distance but where the size varies with the color. There are other aberrations which can vary with color, for instance spherical aberration. These can also produce color fringes but they may vary in different ways from simple chromatic aberration. 



Richard Knoppow
dickburk@ix.netcom.com
Los Angeles, CA, USA