speed and f/stop

Discussion in 'Beyond the Basics' started by danalec99, May 14, 2004.

  1. danalec99

    danalec99 TPF Noob!

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    Another dumb query :)

    The viewfinder (SLR) would not let you know any differences in the aperture/speed settings, since by default the aperture is wide open when we look thru the viewfinder.
    How do we know what speed and f/stop that should be used for each shots?

    Or is it that we need to pick the skill/knowledge of numbers up by trial and error?
     
  2. ksmattfish

    ksmattfish Now 100% DC - not as cool as I once was, but still

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    Many cameras have DOF preview, which closes the aperture down so you can actually see the DOF. Of course light drops too, so it can still be hard to see. And you can always use a DOF scale. Search for "DOF calculator" if your zoom lenses don't have a DOF scale.

    Affects of shutter speed must be imagined, because they can involve capturing images that represent differences in the way we perceive time.

    Practicing definately helps. With experience will come a more intuitive sense about what the results will be.
     
  3. malachite

    malachite Heavily Medicated For Your Protection

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    The meter just calculates everything from the lens' widest apperature at whatever shutter speed you're set at. Late model cameras have more elaborate computers in them so you're just pushing buttons or turning a small knob to select aperature. Older cameras like the Nikon FM2N actually have a ring on the lens mount that engages the AI tab on the lens to manually compensate for the aperature opening even though it remains wide open while your turn the aperature ring. Press the shutter and the lens steps down to the aperature you selected.

    Basically it's like this: You're using a handheld lightmeter on something and it's reading 1/250sec shutter speed at f/5.6 Your lens is a f/2.8 You set your shutter speed at 1/250sec Your camera is now looking at your subject with a 1/250sec shutter speed at f/2.8 The meter is saying f/2.8 is too small of an f/stop and that's when you see the + mark in your viewfinder, telling you to stop down. 2 stops down to f/5.6 you'll get that happy O symbol that says you've got it. Press the shutter, the aperature stops down to f/5.6 for the shot, and then returns to wide open (f/2.8) for further clear focusing delight.
     
  4. danalec99

    danalec99 TPF Noob!

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    I have 10D which I bought recently. Need to figure out a lot of stuff.
    But, does it have this DOF Calulator?
     
  5. malachite

    malachite Heavily Medicated For Your Protection

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    Go HERE. Read it, Learn it, Love it :p
     
  6. danalec99

    danalec99 TPF Noob!

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    Thank you! :)
     
  7. mrsid99

    mrsid99 TPF Supporters Supporting Member

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    The 10D has a DOF preview button just below the lens release button.
     
  8. danalec99

    danalec99 TPF Noob!

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    Yes, I tried that and it is beautiful.

    I also found out that when you press the shutter button halfway, you could see the DOF preview and make the relevant changes right then.

    Thanks, I really am smiling!! :)
     

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