Bolex H8 rex lens, how to use the aperture preset mechanism?

[Liangsi Wang]

I just got a h8 reflex with Kern lens. There is two levers on the lens, I think they are for aperture preset. When these two are pushed together, the aperture is locked at wide open. I don't know how to separate them, therefore, I can't change aperture on the lens. Does anybody know how to fix this? I don't want damage anything

[Dom Jaeger]

The black lever controls the aperture, the silver lever is a sort of stop lock that limits the travel of the black lever. If you move the black lever right up next to the silver one and then squeeze them both together, you should be able to move them as a single unit to set the range. So if you move them both to the minimum aperture stop, you should then be able to move the black lever by itself through the whole range of f stops. If you set the silver lever at say f/5.6, you can move the black lever (and thus the aperture) between wide open and f/5.6. The silver lever should only move when pinched against the black lever, the rest of the time it is locked in place.

If you find them very hard to move, the lens needs a service. I just had to service a H16RX 75mm pre-set Switar for that very reason.