[LargeFormat] Rodenstock Sironar 180mm f5.6 - Convertible

[Clive Warren]

Just been clearing out various places in the house - well this is my 
holiday this year. Short straw possibly......

Anyway, I cheered myself up by finding a couple of lenses that came 
along in a deal a while ago and had been put away safely in a 
previous tidying frenzy.

One of these is a Rodenstock Sironar 180mm f5.6 in a Copal #1 - 
checked the coverage when it arrived - 234mm. Can double up for 4x5 
(it would have to be pretty special to replace the 203mm Ektar) and 
5x7 with minimal movement.

The interesting thing I have just noticed is that it appears to be a 
convertible lens. I tend to prefer mainly the Schneider offerings so 
was a little surprised to see a dual set of apertures on the aperture 
scale - for example, f16 (in white) corresponds to f32 (in yellow).

The yellow scale is marked f=550 - so it is a convertible - 
180/550mm.  The aperture for the 550mm configuration is f16. The 
front element sets are a lot larger in diameter than the rear. 
Folklore and Ken Hough always tells us to put single element sets 
(from Turner Reichs) on to the rear of the shutter. The question is, 
which element set (front or rear) on the Sironar should be used for 
the 550mm focal length?

Cheers,
        Clive