How does the aperture in a lens reduce the amount of light with out making the picture smaller?

Question

I've been a proffessional phtographer for 2 years now but I've never worked out how apertures in camera lenses work. If I look at one of my lenses. I can see the aperture getting bigger and smaller inside when I turn the aperture ring. But how does the aperture reduce the amount of light going through the lens without 'cropping' the picture?

Answer 1

It's the same effect as a pin-hole camera. The lens actually directs the image through the hole, but as it passes through the hole, it is completely diffused, so instead of cropping the image, it removes a mixed up piece of it, whereas all the points of light of the image are going several different directions to begin with. once the image crosses the focal point, the light angles are divided again into their proper order, but instead of being a smaller image, a certain percentage of the light points have been removed.

A better way to explain: It allows only the light that is traveling directly at the apperture to reach the film. The entire image is displayed, because light is reflected in all directions.


I wish I could be more visual.

How about this: The earth only recieves 1/1,000,000th of the sun's light. If you were to put a large, flat sheet between the earth and the sun, and make the hole big enough so that someone on earth can see all of the sun, but nothing more, the sun would be perfectly focused through the hole, but the rest of the earth would not recieve any light. A lens, in turn placed just behind the hole, would spread the light out across the enitre face of the earth, but because it is spreading it, it would not be as bright. Does that help?

Answer 2

Works exactly like the ires in the eye, you squint when looking at the sun its small ,the in the dark it opens up large to allow more light so you can see , works the same on a camera when you squint you still see the big pitcher but your eye is cutting out all the light so it can see the item or what ever your looking at both work the same this why they are medically termed the same way and mean the same great question

Answer 3

You've answered your own question. The diaphram lets less light in, not less image in. The camera lense sees a certain amount of information whether the diaphram is open or closed.

When you squint your eyes, you see less light, but the image in front of you is still there. All the scenery, objects, people, etc. It's just darker.