Copal buzzing sound cocking with preview open

[steen22]

I recently acquired two Nikkor lenses, both with Nikon branded copal 0 shutters. For one of the shutters, when I cock it with the preview open, it makes a buzzing noise that is intermittent if I jiggle the cocking lever.

My other Nikon shutter is entirely silent, doing the same thing, and makes a quick zip sound when I close the preview.

Both are accurate and fire reliably. Should I be concerned about the buzzing sound?

[Kevin Crisp]

I may be wrong on this, but I always thought cocking the shutter with the shutter open on preview was an improper way to do it. I don't like the strained sound it makes. Nearly all of mine will make this sound, but I never do this to them. There is no reason to that I can think of.

I know an ancient camera repair guy, I'll ask him.

[paulbarden]

Don't cock the shutter when it's in preview mode.

[BrianShaw]

If I'm not mistaken, the buzzing sound is the slow speed escapement getting manipulated when you are charging the shutter. It's not clear to me that charging while shutter is open is a problem, per se, but I agree that it's probably not the best practice. I don't like the sound of "the strain" either. :)

From the Copal No. 0 instructions:

246078

[steen22]

I agree that it's best avoided. Just found it interesting when I came across a shutter that doesn't make the straining noise/or is a lot quieter.

[BrianShaw]

You may want to consider the possibility that the shutter making the intermittent sound might benefit from an overhaul.

[domaz]

Agree that if you hear the slow speed escapement doing this it probably means you need a CLA. The shutter might work at slow speeds fine in studio conditions and fail to work in the cold is my guess because it's taking too long for the slow speed escapement to adjust.