Exposure question

Discussion in 'Beyond the Basics' started by dzuy, Jan 23, 2006.

  1. dzuy

    dzuy TPF Noob!

    Joined:
    Jan 23, 2006
    Messages:
    6
    Likes Received:
    0
    hi everyone,

    a little new to photography. i just picked up the s80. i understand basics such as aperature, shutter speed, white balance.

    i have a few questions though.....

    1) exposure is interdependent on shutter speed and aperture. Say i adjust my shutter speed and aperture. then i alter the exposure increments. does that mean my aperture and shutter speed changed with my exposure change?

    2) aperture priority mode and shutter speed priority mode, are they basically the same thing? in aperture mode, whatever you choose, an appropriate shutter speed will chosen for you, and if you are in shutter speed mode, the aperture will be chosen for you.... so technically the 2 gives you the same results?

    thanks!
     
  2. markc

    markc TPF Noob!

    Joined:
    Mar 8, 2004
    Messages:
    4,237
    Likes Received:
    6
    Location:
    Rochester, NY Velocity: Unknown
    Can others edit my Photos:
    Photos NOT OK to edit
    Film/sensor speed (ISO), aperture, and shutter speed are what make up exposure. ISO is how quickly light is "absorbed" or sensed. Aperture is how big a hole it goes through, and shutter speed is how long it goes through that hole. If one changes, one or the other or both of the other two have to change in the other direction to keep the same total exposure.

    You have it right for number 2. You should end up with the same exposure whichever you use.
     
  3. cecilc

    cecilc TPF Noob!

    Joined:
    Mar 24, 2004
    Messages:
    51
    Likes Received:
    0
    Location:
    Atlanta, Ga USA
    With deference to Mark (who's opinions and advice are always respected) ....

    AV and TV are not the same thing. While you may wind up with the same exposure value in your shot, the two settings are used for different purposes.

    TV mode is used to control the shutter speed, which controls how quickly the scene is captured. If you're shooting static subjects a shutter speed of 1/60 will probably be OK .... but if you're trying to "stop" a running dog, then you're going to need at least 1/500 to do that ....

    AV mode is used to control depth of field. If you're looking for a shallow DOF, then you'll open up your lens to 2.8 or so to do that. If you want to expand your DOF, then you'll stop down your lens to 8.0 or higher.

    As I said, shooting the same scene using the two modes with different settings may give you the same exposure value, but it won't be the same exposure ..... they will look different based on shutter speed or how open or closed you've set the aperture value.

    They are distinctly different settings used for different purposes ....
     
  4. ChopstickHero

    ChopstickHero TPF Noob!

    Joined:
    Jan 17, 2006
    Messages:
    159
    Likes Received:
    2
    Location:
    Redlands, CA
    great explanation.

    dzuy: here's a site giving an almost "plain english" explanation of photography terms, techniques, etc. a few articles helped me out. http://www.kenrockwell.com/tech.htm
     
  5. markc

    markc TPF Noob!

    Joined:
    Mar 8, 2004
    Messages:
    4,237
    Likes Received:
    6
    Location:
    Rochester, NY Velocity: Unknown
    Can others edit my Photos:
    Photos NOT OK to edit
    I saw that, but he went on to explain that he understood that they weren't exactly the same, and I was thinking in terms of exposure.

    In my mind, the exposure value is the exposure. It's how much the light in the scene is exposed. Yes, aperture and shutter speed will have an affect on other aspects of the image, but if the camera's meter is working correctly, the overall exposure of the image will be the same.

    Maybe we are using the term differently. For me, exposure only deals with light. DOF, motion blur, etc. would fall into composition.

    But thanks for clarifying AV vs TV. I ended up skipping over the differences.
     
  6. markc

    markc TPF Noob!

    Joined:
    Mar 8, 2004
    Messages:
    4,237
    Likes Received:
    6
    Location:
    Rochester, NY Velocity: Unknown
    Can others edit my Photos:
    Photos NOT OK to edit
    Man, after reading that again, it's sounds pretty snooty, but I'm not sure how to change it. My brain doesn't work like it used to, so I'm sorry if it came across that way.
     

Share This Page