PETRI 7 - INTERIOR SHUTTER

The shutter is the part that lets the light beams reach the film, for only a fraction of a second. So normally the shutter is always closed, only when you trigger it (press the button to take a picture) will the shutter open, and then quickly close again.

Just as with the diaphragm iris, we see three small blades inside the shutter mechanism. These are also connected with a solid part and a rotating ring.

So the principle is the same, if we turn the ring, the shutter will open. But in order to have a working shutter, the blades need to block the light again. So the ring has to rotate forward and back, all in a blink of an eye.

the rotating ring on the other side

the rotating ring on the other side

How exactly? Well, earlier we saw that we need to wind the film before we can take a picture. By winding the film, you are also cocking the shutter mechanism. You remember the part that of the film winding mechanism that was connected with the shutter? Here we see it again.

here you can see how the mechanism is blocked, and the spring is pulled

When the trigger is pulled, the mechanism will unblock, and begin rotating. Now you can see the shutter opening and closing. To see things more clearly, I removed one of the blades.

the shutter is cocked -> the shutter is closed

the mechanism is unblocked -> the shutter opens

the mechanism is fully rotated -> the shutter is closed again

Now here's' the tricky part. There are two small L-shaped parts that are each under tension by a small piece of curved ironwire. Between these two parts, is a small cylinder sticking out of the rotating ring where the blades are connected on.

the two L-shaped parts

Then there's the large part that is connected with the winding of the film, and the large spring. This part begins rotating, and hit's the two small parts in a certain order.

The first small part will make sure the blades open by rotating the ring on the other side. The second small part makes sure the rotating ring is turned back, meaning the blades will close again.

here you can see the rotating ring hitting one of the small L-shaped parts

each L-shaped part is able to rotate, each in a opposite direction