T3D matched fls

[John Toeppen <toeppen@xxxxxxxx>]

Rays asks:
Of course, I will
be buying them in pairs.  I have been led to believe that normally
available commercial lenses may vary considerably in their
characteristics,even their focal lengths.

David White used to sort and match. 
I would go with a high volume lens (something very popular).  If you
were to go to a dealer and get sequential numbers you should do well.
My theory is that lenses are like pancakes - best when produced in high
volume.  High volume allows one to monitor slight drift in tolerances
using statistical sampling methods and exercise appropriate process
controls.  This keeps the drift very small and price low.
On the otherhand, zoom lens are often not much more, and could allow you
to have some W-T adjustments that you lock down. 
Good luck Ray

John Toeppen
http://members.home.com/holographics/


------------------------------