aperture size and shutter speed?

Question by dEviL: aperture size and shutter speed?
How do they work? I get the basic idea. Longer the shutter speed, the more the light will enter and hence the pic is brighter. Larger the aperture size, again more light will enter and make the pic brighter. So my real question is this. Take 2 cases.
Case 1. I set a small aperture size and leave the shutter open for a long time and
Case 2. I set a large aperture size and increase the shutter speed.
Now both the images should look pretty similar right? since same amount of light is entering into the lens? If so, how to decide which option to go for, (case1 or case 2)..?(I’m also guessing that this is what is called aperture priority and shutter priority? I could be wrong)..

Best answer:

Answer by selina_555
You’re getting pretty close in understanding.

As far as light/exposure is concerned, yes, they will look quite similar.

The BIG difference is in DOF- depth of field. If you have a DSLR and a fast lens, you’ll see the biggest difference – not so much in a small P&S camera – and it is one of the most important aspects of using camera settings creatively (as opposed to AUTO).

ETA to explain further:

DOF – Depth Of Field
DOF is the area (plane) of the photo that is in sharp focus. For landscapes, we usually want a a very deep DOF, so that everything in it is in focus. For portraits, we usually like to have the person in focus, while the background is blurred.
So you have a plane that is in focus – and it can be either in the foreground (so the background is blurry) or in the background (so the foreground is blurry).

For the most part, this is achieved via a lens with a large aperture (that’s the small f/stop number), but a longer focal length – i.e. zoom – increases the effect. Often people ask how to achieve with a small P&S camera, but unfortunately that is not something those little things are very good at.

If you have manual controls, use the biggest aperture. If you don’t, try setting it to the portrait setting which makes the camera choose the biggest aperture it is capable of. Make sure there is some distance between you, the subject, and the background. You can also attempt it on Macro setting – that may work to a certain extent.

For further reading, check out this Wikipedia article: http://en.wikipedia.org/wiki/Depth_of_field

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