Hasselblad V lens: Sporadically can't adjust aperture until shutter is cocked.

Hi all,

I have a Hasselblad 250 mm SA CF lens on a non-native body. In order to keep the internal shutter open at all times, I leave the lens in F-mode. About once a month (I use the lens sporadically) I run into an issue where I am using the lens at f/8 and I hear a click from the lens only to see that the aperture is now at f/5.6. Adjusting the aperture ring, shifting the DOF switch on/off, or gently tapping the lens do nothing, the lens stays fully open no matter what. But when I switch out of F-mode, the internal shutter close, and after cocking it again I finally regain full control of the aperture diaphragm. Does anybody know why this is happening? I would like to prevent this from happening as it requires me to unmount the lens from the body and this can introduce dust on the sensor when I am out in the field.

I have reached out to a popular Hassy repair person, who suggested that I contact Hasselblad directly. Hasselblad told me that they no longer service this lens, and that I should exercise the DOF next time it happens. I have tried that and it still did not restore control of the aperture until the shutter was cocked.

Thanks.

From what you describe, the click is the lens shutter triggering. In F-mode, it returns the aperture full open. In C-Mode, it closes the shutter (hence the closed shutter when you switch to C-Mode). You then have to re-cock the shutter.

The cocking mechanism is under spring load to trigger, and is held open by a tiny latch, which has a small spring that holds it in place. When you mount the lens on a Hasselblad body, a pin on the body disengages this latch, thus allowing the key to control the lens. This latch is probably slipping out, or something in the adapter is nudging the latch.

Control key on the left, release lever (triggers the latch) on the right. Swinging the release lever downwards will release the lens shutter, if you try it in F-mode with the lens stopped down, you will see that it opens the aperture.

I have seen cinematographers modify the lens by inserting a piece of cardboard, or sliver of wood beneath the release lever to prevent it from triggering the lens. So obviously what you are describing is not unheard off.