What is an iris shutter in a camera?

Most companies call these shutters "leaf shutters." It's a shutter that's built into the camera lens. It has two advantages and three disadvantages over a focal plane shutter.The advantages are every shutter speed is a flash sync speed, and every lens contains a shutter of its own so if the shutter on your 80mm lens breaks you can mount your 150mm lens and finish the job.

The disadvantages are slower shutter speeds than focal plane shutters will give (Hasselblad 500-series cameras go to 1/500 second and Hasselblad H-series go to 1/800; my Nikon F4 goes to 1/8000), having the shutter in the lens means you have to buy a new shutter with every lens and they are NOT cheap; and at the same shutter speed a focal plane shutter will allow more light to pass, so if you have a handheld meter you have to adjust your exposure to accommodate this.