[rollei_list] Re: 500/5.6 Tele Tessar, APO and DIN 19040 part 5
- From: bigler@xxxxxxxx
- To: rollei_list@xxxxxxxxxxxxx
- Date: Mon, 8 Jan 2007 10:59:05 +0100 (CET)
My 0,02 euro to the New Year's APO discussion
A RUG-er's favourite, just after the planar-vs-xenotar debate ;-)
The (in?)famous DIN standard that allowed some well-known manufacturers to
label 'apo' their photographic lenses is named : DIN 19040 part 5
A "refreshing" exchange between Bob Salomon and Brian Calswell :
http://www.talkaboutphotography.com/group/rec.photo.equipment.large-format/messages/104426.html
Bob S. :
[quote]
> Now the current DIN specification assures that the lateral chromatic
> aberrations in the secondary spectrum, are reduced to a minute
> percentage (not more than o,4% of the focal length at 1:1) of the
> focal length.
[end quote]
Brian C. :
[quote]
Symmetry alone can achieve perfect lateral color correction at 1:1 in
a lens which is not even achromatic. The DIN spec is nonsense, and
would not be acceptable to anyone I know in the lens design/optics
community.
[end quote]
-----------------------------------------
I have no idea whether this German DIN standard 19040 part 5 is still
in use or not, but my understanding is that it allowed Schneider to
label their famous view camera line of lenses APO-Symmar®, a series of
lenses previously called Symmar-S®
--
Emmanuel BIGLER
<bigler@xxxxxxxx>
---
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:
