Excuse me my noob is showing

Discussion in 'Photography Beginners' Forum' started by Computer_Generated, Jul 7, 2008.

  1. Computer_Generated

    Computer_Generated TPF Noob!

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    So I'm kinda not getting the small apature thing. I understand the large ones - it's easy to see. I was doing some reading and read that most landscape pictures are taken with f11/16.... why not 22? The smaller the apature the more dof you have right? So if you're shooting a landscape why wouldn't you pick 22 over 16?

    I think the point shows when people take those stupid pictures of apples when showing DOF tutorials. Setting this noob straight would be a great help.
     
  2. Alpha

    Alpha Troll Extraordinaire

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    In landscape photos you're often focusing at infinity, where there's no real background to adjust the focus/bokeh of using aperture. In a sense, everything is background. At aperture extremes, lenses tend to be softer. That is, wide open or stopped down. Shooting at f16 covers your ass because it flattens the perspective a bit without sacrificing much sharpness, and doesn't flatten it so much that the landscape looks 2D.

    Hope that helps.
     
  3. Miaow

    Miaow TPF Noob!

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    Maybe a bit of a reason also? Not sure lol

    I tend to use small appetures like F22+ to drop light when I'm doing a long exposure (slow shutter speed) pic- You need longer shutter times using a small appeture to get the same amount of light that you would with a wider appeture and a faster time (if that makes sense lol). If you're doing a hand held landscape shot - you most likely wouldn't want a slower shutter speed unless it was on a tripod.
     
    Last edited: Jul 7, 2008
  4. Computer_Generated

    Computer_Generated TPF Noob!

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    that's excellent, I didn't realize that it softens your image. So would that hold true for macros where you want to open it up to get as much light and dof as possible? Or is the way the lens made change how obvious it is?
     
  5. Mike_E

    Mike_E No longer a newbie, moving up!

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    You can have more DOF or you can have more light but not really both.

    Think of a garden hose. As wide open as it gets it's a nice well defined stream that doesn't go very far from the end of the hose. This would be a short DOF.

    As you make the opening smaller you get more force and you get more distance between the end of the hose and the end of the stream of water. More DOF

    There comes a time when the opening of the hose gets too small and the turbulence at the opening causes the stream to break up and you get misting (defraction). This is where the analogy breaks down because light doesn't ever stop (unlike water) and you will still get a larger DOF.

    You will however continue to get more defraction (misting) as you go smaller and smaller in your aperture.

    HTH :)
     
  6. phogan22

    phogan22 TPF Noob!

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    I think it's also true that the smaller the lens (as in focal length), the more DOF for the same aperture. So if you had an 18mm lens at f/5.3 and a 70mm lens at f/5.3 the 18mm would have more depth.
     
  7. Alpha

    Alpha Troll Extraordinaire

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    Other way around. Longer focal length means flatter perspective/more depth of field.
     
  8. Computer_Generated

    Computer_Generated TPF Noob!

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    This is all great information for what I thought was going to be a simple question. Thanks everyone!
     
  9. Alpha

    Alpha Troll Extraordinaire

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    Wide open means shallower DOF. Macro shooters want more DOF, so they stop down. A lot. That's why you'll see a lot of macro lenses routinely stopping down to f.32, whereas most non-macro lenses quit at f.22
     
  10. WDodd

    WDodd TPF Noob!

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    Alpha I think you are a little backwards here. Wide open is the largest opening the lens can achieve which correlates to the smallest F number.

    Small F-number = Large Aperture (lens opening) = Short depth of focus/field
    Large F-number = Small Aperture = Large depth of focus/field

    And as far as focal length goes, the larger the focal length the less depth of focus. Aka 200mm f/2.8 will be shorter than 17 f/2.8. With the longer focal length light has more of a chance to disperse before it hits the sensor or film.

    Camera distance to subject and subject distance to background also play a part in bokeh as well but that is a different story.
     
  11. Alpha

    Alpha Troll Extraordinaire

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    Flattened perspective does not mean DOF is shallower.
     
  12. phogan22

    phogan22 TPF Noob!

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    Right, I think I meant that more is in focus....
     

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