Branch with Lichen, Cambridgeshire
(Nikon D7000 / 50 mm f1.8 - 1/320th / f2.8 / ISO 160)
Getting Started - #5 - Aperture - The Hole in Your Camera's Eye
If the camera's shutter is a bit like your eyelid - it opens & closes allowing light to enter the camera. Then the aperture of your camera lens is like the pupil of your eye. And like your pupil of your eye the aperture of the lens can vary in size (in fact, in diameter) from large to small.
A large aperture - your pupil being wide open - lets in lots of light - good for when there is not so much light around.
A small aperture - your pupil being very small - cuts down the amount of light getting in - good for very bright scenes - say outside in bright sunlight.
Now, this is where it gets a little complicated. But just accept it. Because of the way aperture is defined, a very large aperture number - called an f number in camera-speak - means the aperture is very small.
And a very small aperture number - means the aperture is very large.
Large f number = small aperture.
Small f number = large aperture.
Just think of it as bigger f numbers mean the lens is good at cutting down the amount of light getting into the camera.
And smaller f numbers mean the lens is good at letting lots of light into the camera.
So a lens set at f 32 - has a small aperture (because 32 - here - is a big number) - and this small f 32 aperture is good at stopping lots of light get into the camera. So you might use this high f number setting when the scene is very bright.
And for a lens which has its aperture set to f 2.8 - a large aperture (because 2.8 is a much smaller number than 32) this means the lens lets lots of light into the camera - good for poorly lit scenes, at night, at concerts.
And it is the lowest f number setting - ie the largest aperture of a lens - that makes a world of difference to your photography - and to the price of your camera or lens.
The lower the f number of a lens, the more flexibily you have with its other 2 dancing partners, shutter speed and sensor sensitivity - to get the picture you want in low lighting conditions.
All cameras can take good pics in good light.
Where the rubber hits the road is in the camera & lens combination's ability to take acceptable pics when the light is poor - at night or indoors.
At the 'Getting Started' stage you can largely ignore aperture - but you can't ignore shutter speed as shutter speed - if it is too low - say longer than 1/100th of a second - can lead to blurred pictures.
And if your camera lens has only a medium sized maximum aperture - say f 3.5 or f 4 or even f 5.6 - that means the shutter speed gets longer (ie more chance of blurring) more quickly than if you had spent even more money and bought a camera lens which has a large maximum aperture of say f 2.8 or f 1.8 or f 1.4 or even f 1.2.
So why don't we all have camera lenses which have large maximum apertures like f 2.8 or f 1.8 or lower?
Answer - Expense & weight!
Such lenses - often called 'fast' lenses typically cost lots of dosh and are often very heavy.
A professional photographer will use such heavy & expensive lenses because they increase the chances of him getting the shot his editor wants - but for those of us with kids to feed and a mortgage to pay - we live with more affordable lenses with smaller maximum apertures.
At the 'Getting Serious' stage, you will want to be able to use different apertures to get different effects but that's for another post.
But at the 'Getting Started' stage you just need to know that aperture is one of the key dance partners with shutter speed.
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