distance and light

Discussion in 'Photography Beginners' Forum' started by julie32, May 23, 2008.

  1. julie32

    julie32 TPF Noob!

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    Hi guys,

    I need some basic assistance. Trying to take a photo in really bad inside flourescent lighting of a person about 5 feet from me and then a person behind them an additional 2-3 feet. For the life of me, I couldn't get them both in focus. (I shoot with a canon 5d, 580 ex, 24-70 2.8). I tried increasing the ISO but I didn't want graininess..... I settled at 400. I tried decreasing my F-stop, but the shots were too dark.
    How should I have approached this?

    Thanks for any help you may provide

    julie
     
  2. *Mike*

    *Mike* TPF Noob!

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    You've got a DOF problem... And as with anything, it's a tradeoff. You could've raised your ISO further - so that you could've stopped down your aperture. You could have used flash and overpowered the ambient light, and shot with a small aperture. Or, you could've gone with a shorter focal length, which would've increased the DOF but possibly introduced wide angle distortion or framing/composition issues...
     
  3. Alfred D.

    Alfred D. TPF Noob!

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    ISO 400, F/11 or F/16 aperture priority, tripod, selftimer, and subjects sitting very still!
    Longer distance to subject, thus longer focal length used, is a more flattering perspective for people and faces.
     
  4. julie32

    julie32 TPF Noob!

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    Hey Alfred,

    I wish I was under those circumstances...but I was shooting an event and I was trying to get the speaker at the mike close to me as well as the person's facial expressions behind him.....I just couldnt get them both in focus which was totally frustrating.
    I'm relatively new at this (few years) so I'm still learning....
    I did have my flash on though.... I'm so bummed the photo stinks.

    Thanks for the reply
     
  5. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    Your Depth of field was too thin. To increase your DOF, you need to stop down your lens (higher F number). When you do that, you lessen the amount of light getting in, so you (or the camera) needs to do one or more of the following: Use a longer shutter speed, increase the ISO, use more flash output.

    In your situation, you should have just stopped down to a smaller aperture and if the flash was in E-TTL mode, it would have output more light. The exposure might not be the same for the two people, but that's another issue.

    Also, the 5D should easily give you very usable images at ISO levels up to 1600. You just have to make sure that the exposure is good.
     
  6. julie32

    julie32 TPF Noob!

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    Really really helpful info Mike, thank you.
    I'm a shaky person to begin with so longer shutterspeeds don't bode well for me without a tri-pod.

    I'm going to practice with your info.

    Thank you!
     
  7. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    When I'm shooting an indoor event like that. I have the camera in manual mode and the flash in E-TTL mode.

    I set the shutter at somthing around 1/80 or 1/125. That should prevent most blur.

    Then I set the aperture based on the DOF that I want. You don't have to really worry about the exposure because the flash will automatically adjust it's output to the aperture that you are using. If the exposure is off, then I use FEC to adjust the flash.

    If I want more ambient (background) exposure, then I will use a longer shutter speed (being cautious of blur). If I want less ambient exposure, then I will crank up the shutter speed to the max sync speed (1/250 on my camera).
     
  8. julie32

    julie32 TPF Noob!

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    Mike,
    What do you mean when you say the "if the exposure is off"....off like a button you turn on or off....or off like not looking right? Clarify that for me. I think I need to fully understand DOF because I'm not understanding the relationship between aperture and DOF correctly. I imagine there is some mathematical equation to figure that??

    thanks....so much
     
  9. Socrates

    Socrates TPF Noob!

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    In theory, the only portion of your photo that's in focus is a plane of zero thickness. Anything closer than that plane is out of focus as is anything further away than that frame. In reality, the human eye is very forgiving and, in an oversimplification, DoF is that portion of the image in front and behind the focus plane that will appear to be in focus. Everything else is blurred.

    IF NOTHING ELSE CHANGES...
    Larger aperture (smaller "f-number") means smaller DoF

    IF NOTHING ELSE CHANGES...
    Longer focal length means smaller DoF

    IF NOTHING ELSE CHANGES...
    A closer subject means smaller DoF

    IF NOTHING ELSE CHANGES...
    A larger picture frame means smaller DoF
    (You can't change this at will - it's fixed with the camera.)
     

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