What are Iris in lens?

i want to know about. exactly what is an iris in lens?

What are Iris in lens?
The iris in a camera lens is the diaphragm, normally of thin flexible plates, that forms the aperture. Adjusting the amount that the iris is opened alters the amount of light that is passed through the lens. The aperture and iris are complementary - the aperture (hole) is formed by the iris (diaphragm). The larger the aperture, the smaller the effective width of the iris blades. At the lens' smallest aperture, the iris will almost completely cover the lens surface.
Reply:mmmm...ok...


your eye has an iris. It's the coloured bit, mine are brown by the way ... :o)





The iris opens and closes: It closes up if the light is too bright. It opens up to let more light in so you see more detail, when it's darker.


In your eye the 'pupil' appears to be the black dot in the middle of you iris.


The lens is in front of both the iris and the gap [pupil] you view the world through, focusing automatically on the things around you [unless you need glasses!].





In photograpy, the IRIS in a camera is just like the iris in your eye, except you can manually set it to open to let in more or less light, if it is not an automatic one. Sometimes the Iris are called 'shutters' and they are behind the lens.


The LENS is what you use to focus the main subject of your photo shot [these can also be automatic]. The Lens is the bulbous, rounded glass on the front of a camera [not the bit you look through].





Expensive cameras have buttons or levers for adjusting the FOCUS of your LENS.


They also have buttons or levers for adjusting the length of time your IRIS stays open for, which is the AMOUNT OF LIGHT the iris lets into the camera [exposer].








SO:


...the Iris is behind the Lens and lets in light.


...the Lens is used to focus on the world.