Re: Elmarit 90mm

[Paul Schliesser <paulsc@eos.net>]

>Its a bit confusing but 00 means 90.0.  90 means 89.0.  if the number is
>less than 50 insert a decimal point between the two digits and put a 9
>in front of it, otherwise insert the decimal point and put an 8 in
>front.  Thus the maximum variation in focal length would be 5 mm.  In
>practice its never this far off.

Dennis,

I went and looked it up and you're absolutely right. I had always thought 
that you added this number to the marked focal length, but as Dan pointed 
out, unless some are marked with negative numbers, you can't indicate a 
slightly short focal length with that system.

The two numbers are in tenths of a mm, and they are the last two digits 
of the focal length if you put a decimal point between them. So my 50mm 
Summilux, marked 14, is 51.4mm, my 135mm Elmarit marked 44 is 134.4mm, 
and the 90mm marked 90 would be 89.0mm, not 99mm as I had thought.

I have not paid attention to these numbers, once I had found out what 
they meant. What made me remember the Elmarit with the 90 marking is that 
99mm (which is what I thought it meant) seemed to me like a pretty big 
deviation from the marked focal length. I also thought it might be an 
indication that there was an unannounced recomputation of this lens that 
nobody had noticed before, since I saw otherwise idential lenses 
(including mine) marked 00. That seems like less of a big deal now, 
knowing that they are only 1mm different in focal length.

35mm and shorter focal lengths don't seem to be marked, at least on the 
ones I've got to look at.

- - Paul