Apertures and F-Stops?

Question

I know this is a silly thing to ask when I want to be a Photographer, but I still don't understand apetures and f-stops on a camera. What are they, and how do they work, and how do you know which settings to use to take a perfect picture?

Answer 1

Imagine the aperture as the hole in the lens through wich the light that hits your film comes in. The size of an aperture is indicated by its f-number or f-stop. Lenses come with a limited range of apertures (f-stops). The smaller the f-number, the larger the hole in the lens. On most manual cameras, the widest aperture is f/1.4 and the smallest one is f/16 (although some automatic and semi-automatic cameras also have f/22 and f/32). An f-stop is nothing but the f-number (size of the aperture). If my available f-stops are: f/1.4, f/2, f/.2.8, f/4, f/5.6, f/8, f/11 and f/16 and my aperture is currently set at f/1.4, if I change it to f/2, I'll increase it by one f-stop (but my aperture will, in fact, become narrower).

To take perfect pictures, you need to combine your aperture with the correct shutter speed. If your aperture goes up X stops, your shutter speed goes down X stops. If your aperture goes down X stops, your shutter speed goes up X stops.
The stops for shutter speed are:
1/15 (slowest), 1/30, 1/60, 1/125, 1/250, 1/500, 1/1000, 1/2000 (fastest).

Hope this helps!

Answer 2

The aperture of a camera is the apparatus that controls how much light makes contact with the film in the camera. When you are adjusting the aperture always think in opposites. The smaller the number on you aperture setting dial the larger the hole in the lens, which means more light is hitting your film. The F-stop setting is also called the shutter speed. The Shutter is the device in the camera that regulates the amount of time the light entering through the aperture can touch the film. But basically if you have a light meter on your camera or a handheld one the light meter will tell you exactly what settings to use. When you start taking photo classes you will have to get used to it, you will take a lot of bad photos before you start to get better. But with experience you will learn how to use a manual camera very well. Good luck to you

Answer 3

This is a tough concept for a lot of young photographers so don't feel alone.

Let me try to answer this one in basic terms...

Let's say there is a perfect shutter speed/ f-stop combination for each photograph ever made.

The exposure is based upon the idea of a target exposure....in most cases it is 18% gray. Now the camera has it programed into its exposure meter that the proper exposure for most situations is this perfect 18%. So the changing of the shutter speeds and f/stops are made to reach this 18%.

As in the previous answers the f/stop or aperture ring allows a define amount of light to the sensor or film. F/22 allows only a small fraction of the light to enter while f/2.8 allows a lot of light.

Shutter speeds work in whole or fractions of seconds.

So what you're trying to do is create the correct combination of these two controls.

Let's say the "proper" exposure for a scene is 500th and f/5.6.
It's sunny outside...no clouds. Well, other "proper" exposures would include: 250th at f/8 or 125th at f/11 OR 1000th at f/4.

If you slow down the shutter speed (500 down to 250) that would allow more light to the film. To compensate and get the "proper" exposure you would have to decrease the amount of light reaching the film. This is where its gets weird. To decrease the amount of light you have to "increase" the f/stop to f/8. Does that make sense. If you have a DSLR or can look at a lens off of a DSLR you can play with the aperture ring and watch as the iris of the lens gets smaller as the numbers go up....(I didn't make up the system but that is the way it works.)

But this is where the control comes in. The f/stop controls what is called Depth of Field. This is the area that is in focus at any given f/stop. An f/2.8 has a very shallow or thin depth of field...while at f/22 there is a very large depth of field. If you want things in focus only in the foreground (like a portrait) you would use a shutter speed/f-stop combination that would give you an f/stop of 2.8 to 4.0. If you want the person and every thing behind them to be in focus you would increase the f/stop to f/22. Now to get the "proper" exposure you would have to slow the shutter speed down to allow more light to get to the film (ie. 500 at 2.8 would become 1/8th at f/22) Both of these frames would be properly exposed. BUT (there are a lot of buts in photography) At that slow a shutter speed you would need a tripod to hold the camera still. So you would want to increase the shutter speed to say 60th of a second. Now to get the "proper" exposure you would change the f/stop to f/8.

Here are the combimations:

500 2.8
250 4
125 5.6
60 8
30 11
15 f/16
8 22

Now lets say you move to a shaded area and the meter reads
30th at f/4. That's a little hard to hand hold so you increase the shutter speed to 60th........now the f/stop is what? If you said F/2.8 you would be right!

Does that make any sense? It's really not hard if you just get it into your head that there is no "perfect" combination of shutter speeds and apertures.......just a bunch of combinations that give a "proper" exposure to one target...18% gray.

Answer 4

Still too complicated:

Aperture ("opening") and f/stop refer to the amount of light your lens lets into the camera. The smaller the number, the bigger the hole:

f/2.8 = lots of light, a wide open lens.
f/22 = a little opening.

If you have a lens, take it off the camera, and look into the back while you change the f/stop. You'll see the little aperture get larger and smaller.

f/stop refers to a ratio. Aperture just means "opening."

The darker it is, the more light you need to admit. See the other posts for more detail about depth of field and film speed...and feel free to contact me for more--here's a link to a couple of my photos.

Answer 5

wow, these answers were way complicated. here's what i tell my students: aperture and f/stop are essentially the same thing. the terms are often used interchangeably. aperture is the actual opening in the lens (it'd be expressed in milimeters). lower #'s equal larger openings, higher #'s equal smaller openings. f/stop is the ratio between the size of the aperture and focal length (distance from lens to film). f/stop is expressed as 2.8, 5.6, etc.
now for how they work: the 'perfect' picture depends on a lot more than f/stop. f/stop determines depth of field in your picture. depth of field is how much of the picture plane is in focus. lower f/stops give shallow depth of field. this where the subject is in focus but the background is blurred. higher f/stops give greater to infinite depth of filed where all areas of the picture plane are in focus. so your 'perfect' picture depends on what you want to emphasize as to which f/stop you choose.
manual focusing is largely dependent on your aperture. larger apertures (openings in the lens) are less 'forgiving' when it comes to focusing. this translates into a shallow depth of field. less of the picture plane is in focus. i.e., subject is 6ft. away, your aperture is large (f/2.8) but you focus at 10 ft. your subject will be out of focus. with a high aperture focusing is more forgiving. subject is 6 ft. away, but you focus at 10 ft. using a small aperture (f/22). your subject is in focus because small apertures provide greater depth of field.
pinhole cameras use extremely small apertures (usually with a 5" focal length you'll have f/175). this is why pinhole cameras always have infinite depth of field despite not having a lens to focus.
p.s. you will never see aperture expressed in milimeters (except occasionally in pinholes for purposes of determining f/stop). aperture or f/stop are always expressed using the f/stop terminology (f/5.6, 8, 11, 16, etc).

Answer 6

try here this may help
http://www.daveread.com/uw-photo/exposure101/digression1.html