I have a Bessa RF which has two red windows. My assumption is the second one is for 6X9 format. There is a little twisty knob between the two windows which reveals (opens up) the first but not the second window. Am I correct that the second window is for 6X9? How does one get it to open? I am familiar with the various Bessa folders and this one is the RF, all black with separate rangefinder and viewfinder, made from the mid 30s to early 50s. It is not a Bessa I or Bessa II. Any ideas on solving this mystery? Bill Barber

OK -- not much better than "informed speculation" here, but some other 6x9 cameras can be fitted with a mask to do 645 format. According to an electronic Bessa I manual I have here, the second window stays shut unless the 645 mask is installed (pretty durn clever for 193x!). This was on a CD I bought to get a Perkeo II manual; it has many others, but alas, not the RF. I would tend to assume the RF of similar vintage would behave similarly.

With my Ercona II (not that sophisticated) you wind the number to the red window closest to the supply spool; e.g., away from the winding knob, then if shooting 645, wind that same number to the second window for the next shot. But other than a little switch to alter the viewfinder, there is no magic interlock for 6x9 vs 645. (Alas, since I don't own the mask, I've never gone that way.)