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