aperture help

topcatz200

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hi all , can some tell me in simple layman terms about aperture as i get very confued about it. how do i get everything out of focus ? is it using an aperture of 1.3/ or 2.5 and everything in focus aperture of 22 / or 30 ? or is it the other way around ? sorry but i do find that my head cant get around this ... lol im ok with shutter speed but aperture goes way over my help, so any help is a BIG PLUS thanks guys !! x
 

Austin Greene

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Aperture value, shutter speed, and ISO all make up the exposure triangle, as in they all affect your exposure. Simply put, aperture is how "open" the aperture in your lens is. The lower the value, f/2.8 for example, the more light is let in, because the aperture is more open. A wider aperture will give you more blurring of your background due to a shallower depth of field. The larger an aperture value, f/22 for example, the less light is let in (which means you'll need a longer shutter speed), because the aperture is more closed. A larger aperture value will give you more depth of field, and will keep your background more in-focus. For example, if you wanted to take a photo of a flower with the background blurred, you would need a smaller aperture value (say f/5.6), and if you wanted to take a landscape (lots of things in the distance in focus) you would use a larger aperture value such as f/11.

Its a basic explanation, and I left a lot out about how the exposure triangle works with interactions of aperture and shutter speed, but it should give you a start.
 

analog.universe

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A larger aperture, means a larger physical hole through which the light passes, so you get more light. A larger aperture corresponds to a lower f-number, because that number is actually a fraction. Let's say you've got a 50mm lens. At f/2.0, that's 50mm/2.0, so the aperture hole itself is 25mm across. At f/8, it's 6.25mm across. As you make the aperture smaller (higher f number), your depth of field increases, and more of the image is in focus. Less total light is captured however. To blur the background, you want a very shallow depth of field, meaning a low f-number or large aperture.
 

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Last edited:
OP
T

topcatz200

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thanks for the help guys
 

MReid

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2.8 big hole lets light in fast...so short depth of field and high shutter speed...hand hold
22 small hole lets light in slow....so deep depth of field and slow shutter speed....tripod
 

jwbryson1

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People (Noobs) come on this forum asking all sorts of questions on ISO, aperture, shutter speed, etc. that is simply "one click" away on Google. I don't know why they don't just Google this stuff and do some reading. Everybody wants to be spoon fed these days.
 

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F/2 is a larger number than f/16 is because f/whatever number, is a fraction.

The f is equal to whatever the focal length of the lens is.

If the lens focal length is 50 mm, at f/2 the lens aperture is 25 mm wide - 1/2 of 50 mm. If the lens focal length is 100 mm, at f/2 the lens aperture is 50 mm wide - 1/2 of 100 mm.

So, many out there have a variable aperture f/3.5-5.6, 18-55 mm zoom lens, and f/3.5 is a wider aperture than f/5.6 is.

At 18 mm and that focal length's widest f/3.5 aperture the lens opening is 18/3.5 = 5.14 mm wide.
But at 55 mm, and it's widest aperture f/5.6, the lens opening is 55/5.6 = 9.82 mm, almost twice as wide as 18 mm and f/3.5 was.

Because, the focal lengths were not the same.

My point is, many people don't make the effort to understand what the numbers are telling us.
 

DiskoJoe

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bigger number equals smaller hole and larger depth of field. (o)

smaller number equals larger aperture and smaller depth of field. (O)

For a portrait you could use 1.4

for a landscape you could use 22.

This varies depending on how much light you have but this is about as simple as it gets.

If you really dont understand this just set your camera to auto and review over the exif data after you take shots. It will give you a round about estimate of what you should be doing.
 

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Until you understand how aperture, shutter speed, and ISO relate to each other just put it on Aperture Priority, set it to f/8 and NEVER CHANGE IT.
 

longjon75

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i had the same problem and i bought a book called UNDERSTANDING EXPOSURE that will help ;)
 

table1349

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2.8 big hole lets light in fast...so short depth of field and high shutter speed...hand hold
22 small hole lets light in slow....so deep depth of field and slow shutter speed....tripod

Light only travels at one speed, that being the speed of light or approximately 186,000 miles a second. What you probably meant was that a large aperture lets in a large amount of light whereas a small aperture restricts the amount of light that is allowed to enter.
 

analog.universe

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Light only travels at one speed, that being the speed of light or approximately 186,000 miles a second.

Actually the speed of light varies based on the medium it's travelling through. If it didn't, lenses wouldn't work, the light would go straight through without getting focused.
 

SCraig

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hi all , can some tell me in simple layman terms about aperture as i get very confued about it. how do i get everything out of focus ? is it using an aperture of 1.3/ or 2.5 and everything in focus aperture of 22 / or 30 ? or is it the other way around ? sorry but i do find that my head cant get around this ... lol im ok with shutter speed but aperture goes way over my help, so any help is a BIG PLUS thanks guys !! x
OK, this is about as simple as it gets.

Think of exposure as water. ISO equals the water pressure. Aperture equals the size of the water hose. Shutter speed equals how long you leave the valve open. Bigger hose = more water (more aperture = more light). Higher pressure = more water out of the hose (higher ISO = more light). Longer valve opening = more water out of the hose (shorter shutter speed = more light). Taking things one step farther, to get more water out of the hose in a given time you can use a bigger hose (Aperture) more pressure (higher ISO) or leave the valve open longer (slower shutter speed). If you want a gallon of water you can get it by adjusting any one of the three values, any two of the three values, or all three. They are ALL related and changing any one of them will affect the amount of water (light) that you get.

There are also pros and cons to changing any of the three. Learning what those pros and cons are is what learning about exposure is all about.
 

table1349

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Light only travels at one speed, that being the speed of light or approximately 186,000 miles a second.

Actually the speed of light varies based on the medium it's travelling through. If it didn't, lenses wouldn't work, the light would go straight through without getting focused.

Lenses change the angle that the light travels allowing it to be focused.
 

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