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Exposure - learning

Discussion in 'Photography Forums' started by jools230575, May 3, 2005.

  1. jools230575

    jools230575
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    Hi people!

    Trying to learn a bit more about exposure. I know that the best thing is to just play around but I was wondering if anyone has had experience of the book "Understanding Exposure: by Brian Peterson"

    Or can someone recommend another book?

    Basically what I'm after is a rough guide as to what F numbers are good for certain situations.

    The reason I am asking this is last night I took my first traffic trails picture. My camera was set to F22 with an exposure of around 90 seconds - 2 minutes. A friend thought it was good but reckons I should have set my depth of field down so as not to get the starburst effect (no filter was used on the lens) on the lights in the street.

    Thanks :D
     
  2. Peakoverload

    Peakoverload
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    Yes this is a pretty good book and will make you realise that exposure is a truly huge subject but as long as you know that the smaller the number the larger the aperture and the less of the frame that will be in focus you should be able to follow it without too many problems.


    Well the "Understanding Exposure" will 'teach' you that there is no such thing as one correct exposure only one correct creative exposure. If you had chosen a larger aperture then your shutter speed would have increased so you possibly may not have captured the light trails at all depending on how busy the traffic was that night. As long as the traffic is moving than any exposure above 30 seconds should suffice so yes you could have used a larger aperture. However a shorter dof would knock the background our of focus which may not always work (depending on the subject). To a certain extent you can control the amount of dof you have at a particular aperture depending on what lens you are using. A long zoom lens will produce less dof at f/8 than a wide angle lens at the same aperture so in other words you could use either a wide angle lens or a fixed lens of a shorter focal length (say 50mm) to help not knock the background too far out of focus.

    HTH
     
  3. seany

    seany
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    Well lets say you're in a church ok, and they wont allow flash you're going to want something with a wide aperture just like when you're eye opens in the dark to let more light in the aperture of a lens works the same and some open wider then others.

    The lenses with wider apertures are known as fast lenses, these are around F1.4 to 2.8 and and at that aperture you will get a higher shutter speed because they let in more(that's why they're called fast lenses).


    Lets say you was in that church with two lenses, a 17-40 F4 and a 50mm f1.4

    The 17-40 at F4 will give you a slow shutter speed to allow more light in. But that without a tripod could well mean a blurred shot, and if it's people you're shooting in that church, or a bar, or people outside at night, then the shutter speed will be too slow to stop motion blur..

    That is when you'll need a faster lens wider aperture (smaller F number) that lets more light in meaning you can get faster shutter speeds for photos of people and other moving objects, still objects to where a slower shutter speed would have caused blur with no tripod, but even a tripod cant freeze a moving object you need fast shutter speeds for that and that means faster lenses


    The wider the aperture the more shallow the depth of field is, if you want to bring everything in to focus you'll need a smaller aperture (higher f number) like for group shots or shots with lots of interest in it
     

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