On Mon, 09 Nov 1998 09:11:03 -0500, ira wrote:

>In trying to determine why some lenses are better than others, what is
>the significance of the "Groups/Elements" column listed in all the
>specs? How do I know what a "10/10" is vs. a "11/13", etc?

The larger number indicates the number of elements (separately-made
pieces of glass [or plastic.....;-], the smaller, the number of
groups after some of the elements have been cemented together. More
air-spaces (less difference between elements and groups numbers)
can allow for greater correction of some optical problems, but it
can result in more ghosting and flare... With simpler-to-design
focal-lengths (like 45-135mm for 35mm), there can be advantages in
using fewer elements in slower lenses to optimize image quality.
Even with difficult lenses, a good and imaginative designer
can make an excellent lens with few elements (the 15mm Zeiss
Hologon had only three elements [!!!], and the first-rate Nikkor
16mm f3.5 also has surprisingly few elements, given its extreme
retrofocus design). Sometimes one can predict if a lens will
serve well for close focus by looking at its lens diagram
(symmetry can be good...;-) - and knowing that a cheap version
of a maker's particular lens has fewer than the expensive version
of their lens with similar specs (like the 5-element Nikkor E and
AF 28mm f2.8 vs. the 8-element AIS MF Nikkor) can serve as a guide
to image quality, but otherwise there may be little to glean from
poring over the specs, I think. It may be interesting, but there
is only a loose correlation between number of elements/groups
and image quality.