Does anyone know the filter factor for the filter attached to the front of the Voighlander RF folder? The filters are often missing however mine is not.
I have a 6x9 Bessa 1 that has a rather thick (1/8") yellow filter, that slips over the lens. I increase exposure by 1/2 stop (open up by 1/2 stop) when using it.
This filter looks to be more of a yellow/green and was original to the Bessa RF, this being the predecessor to the Bessa II. It doesn't come off the lens, but rather flips down and out of the way. The cameras were built from the Mid-30s to about 1950. 1 stop. OK, I'll tell my light meter the film is ISO 200 rather than ISO 400.
Mine is not the same filter as it is not built into the camera, and it is a light yellow. The camera does not have a range finder but was built in the mid 1950's and the lens is coated.
Just use a handheld meter (or, a modern digital with a reasonably narrow spot-like meter pattern) and meter something; then meter the same something through that yellow filter. Observe the number of stops difference. --Dave