Red Markings on Som Berthiot Primes

ymkulkarni · February 22, 2009

Hi,

I have 2 Som Berthiot RX Primes that came with my Bolex. The 75mm and the 25mm both have red markings in the middle of the lens with arrows pointing out above/below the 4. I figured that you were supposed to use the red arrows to set the f/stop and focus point but does anyone know what the other numbers stand for and when I would use them. The numbers are in this order 22|11|4|11|22 for both the lenses. Also, the f/stop settings don't click exactly on the 4 but rather click at odd intervals between the various f/stops available. Does anyone know if my lens needs to be repaired so that the markings are aligned? I don't know if this is a good explanation of my problem but hopefully someone has these same lenses and knows what I am talking about. Thanks! :]

Ryan Thomas · February 22, 2009

Hi,

I have 2 Som Berthiot RX Primes that came with my Bolex. The 75mm and the 25mm both have red markings in the middle of the lens with arrows pointing out above/below the 4. I figured that you were supposed to use the red arrows to set the f/stop and focus point but does anyone know what the other numbers stand for and when I would use them. The numbers are in this order 22|11|4|11|22 for both the lenses. Also, the f/stop settings don't click exactly on the 4 but rather click at odd intervals between the various f/stops available. Does anyone know if my lens needs to be repaired so that the markings are aligned? I don't know if this is a good explanation of my problem but hopefully someone has these same lenses and knows what I am talking about. Thanks! :]

Those markings give you a good estimation of how much DOF you have at each F-stop. Handy for figuring out hyperfocal distances and the like. I'd have to see a picture to be positive, but that's what it sounds like it is.

Edited February 22, 2009 by Ryan Thomas