[rollei_list] Re: Lens recommendation
- From: CarlosMFreaza <cmfreaza@xxxxxxxxx>
- To: rollei_list@xxxxxxxxxxxxx
- Date: Wed, 4 Aug 2010 07:28:22 -0300
>.. It becomes also
> clear that the lateral color aberration is more significant for long
> tele-lenses as the Schneider brochure states.
>
> Carlos
>2010/8/3 Richard Knoppow <dickburk@xxxxxxxxxxxxx>:
> Well, since all aberrations scale with focal length the statement about
> lateral chromatic is a bit misleading. Both kinds of chromatic aberration
> are a constant percentage of the image as focal length changes but what is
> important is when only a small part of the image is used as in a long focus
> or telephoto lens. Then the aberrations become magnified along with the
> image. ...
Richard, I don't think all optical aberrations scale with the lens
focal length, in general they scale with the image size because they
become more visible, but it has nothing to do with the lens focal
length, some optical aberrations like the barrel distortion is typical
for short focal length lenses and it tends to diminish according you
increase the focal length.
The specific lateral or transversal color aberration has to do with
the image magnification directly, this aberration causes that the
image size is different for each color, thus the image magnification
depends on the wavelength, the size of the image varies from one color
to the next. In a lens corrected for longitudinal chromatic aberration
the principal planes do not need to coincide for all colors. Since the
focal length is determined by the distance from the rear principal
plane to the image plane, the focal length may depend on the
wavelength even when all images are in the same plane.
Lateral color is specially evident in telephoto and retrofocus lenses,
lateral color is the main cause of the separation between the sagittal
and tangential curves in their modulation transfer functions. The
typical manifestation of chromatic aberrations is color fringing along
boundaries that separate dark and bright parts of the image:
http://toothwalker.org/optics/chromatic.html
Carlos
---
Rollei List
- Post to rollei_list@xxxxxxxxxxxxx
- Subscribe at rollei_list-request@xxxxxxxxxxxxx with 'subscribe'
in the subject field OR by logging into www.freelists.org
- Unsubscribe at rollei_list-request@xxxxxxxxxxxxx with
'unsubscribe' in the subject field OR by logging into www.freelists.org
- Online, searchable archives are available at
//www.freelists.org/archives/rollei_list
Other related posts:
