G
Guest
Guest
Can someone please explain to me (in simple terms) how aperture works and why letting in more light reduces the depth of field? Just something I've always been curious about.
Re: aperture
The aperture setting is controlled by a round iris that lets in more or less light, depending on the size of the opening. Three factors affect depth of field--the focal length of the lens, the aperture, and camera to subject distance (or magnification).
When you focus a lens, you're adjusting the plane of focus so a plane at a given distance in front of the lens forms an image on the film or CCD plane behind the lens. Regardless of the depth of field--there is only *one* (infinitely thin) plane of focus.
However, there is an area in front of and behind the plane of focus that is acceptably sharp. The amount of acceptable blurring is defined as the depth of field and is directly related to the size of the circle of confusion. The circle of confusion is simply the size of an out of focus point on the film plane. In other words, how blurry can a point be before it looks like the entire image is out of focus.
Imagine a cone of light projected from the rear of the lens on the film/CCD plane. The point of the cone is exactly at the film plane and as you move forward or backward from that point--objects become blurred. The aperture restricts the diameter of that cone. Stop all the way down and you have a small hole that makes a very thin cone. Open up the aperture and the cone becomes very fat.
As you move away from the film/CCD plane at a wide aperture--objects go out of focus more quickly because the wide cone represents light rays diverging quickly. With a small aperture the cone is narrow, so as you move away from the film plane--light rays diverge more gradually and objects stay in acceptable focus at farther distances from the film plane.
The aperture setting is controlled by a round iris that lets in more or less light, depending on the size of the opening. Three factors affect depth of field--the focal length of the lens, the aperture, and camera to subject distance (or magnification).
When you focus a lens, you're adjusting the plane of focus so a plane at a given distance in front of the lens forms an image on the film or CCD plane behind the lens. Regardless of the depth of field--there is only *one* (infinitely thin) plane of focus.
However, there is an area in front of and behind the plane of focus that is acceptably sharp. The amount of acceptable blurring is defined as the depth of field and is directly related to the size of the circle of confusion. The circle of confusion is simply the size of an out of focus point on the film plane. In other words, how blurry can a point be before it looks like the entire image is out of focus.
Imagine a cone of light projected from the rear of the lens on the film/CCD plane. The point of the cone is exactly at the film plane and as you move forward or backward from that point--objects become blurred. The aperture restricts the diameter of that cone. Stop all the way down and you have a small hole that makes a very thin cone. Open up the aperture and the cone becomes very fat.
As you move away from the film/CCD plane at a wide aperture--objects go out of focus more quickly because the wide cone represents light rays diverging quickly. With a small aperture the cone is narrow, so as you move away from the film plane--light rays diverge more gradually and objects stay in acceptable focus at farther distances from the film plane.
HorseFilms
Look ma no hands
Re: aperture
Wow. That's all. Just wow.
Wow. That's all. Just wow.
HorseFilms
Look ma no hands
Re: aperture
[quote author=Barry_S link=board=Events;num=1101298004;start=0#5 date=11/24/04 at 08:47:10] In the meantime you can write about the correlation between what women say and what they really mean :
.[/quote]
That's suicide. You even start thinking about it and the next thing you know, they find you dead in your bathroom.
[quote author=Barry_S link=board=Events;num=1101298004;start=0#5 date=11/24/04 at 08:47:10] In the meantime you can write about the correlation between what women say and what they really mean :
.[/quote]That's suicide. You even start thinking about it and the next thing you know, they find you dead in your bathroom.
Bill__Turner
Well-known member
Re: aperture
Barry, excellent explaination, while I certainly understand the issue, I am not sure I could have explained it as clearly without drawing pictures and waving my arms.
Bill Turner
Barry, excellent explaination, while I certainly understand the issue, I am not sure I could have explained it as clearly without drawing pictures and waving my arms.
Bill Turner
TC
Resident Agitator
Re: aperture
[quote author=HorseFilms link=board=Events;num=1101298004;start=0#6 date=11/24/04 at 08:51:45]That's suicide. You even start thinking about it and the next thing you know, they find you dead in your bathroom.[/quote]
That happened to a friend of mine. His girlfriend noticed that he was understanding what the hell she wanted, and then BAM. Dead in the shower.
[quote author=HorseFilms link=board=Events;num=1101298004;start=0#6 date=11/24/04 at 08:51:45]That's suicide. You even start thinking about it and the next thing you know, they find you dead in your bathroom.[/quote]
That happened to a friend of mine. His girlfriend noticed that he was understanding what the hell she wanted, and then BAM. Dead in the shower.
.