When using this, what do I do?

Discussion in 'Photography Beginners' Forum' started by Markw, Sep 6, 2010.

  1. Markw

    Markw No longer a newbie, moving up!

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    Okay, so when using The_Online_DOF calculator..how do I do so? I shoot a D90. This means that I am encountering a 1.5x crop factor. I know this. If I am shooting my 80-200 2.8 at 200mm..with this crop factor, I have a 300mm lens. If I add a 1.5x TC, this would technically give me an equivalent of 450mm. Okay. I understand all this well and good. But, when Im using the DOF calculator, which of those focal lengths do I put in? The 200mm the lens says, the 300mm the 1.5x crop factor or TC gives, or the 450mm the crop factor and the TC actually gives?

    Thanks,
    Mark
     
  2. Dao

    Dao No longer a newbie, moving up!

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    In the DoF Calc link you provided, you do not need to change anything yourself, just enter the actual physical values. i.e. If you use a 50mm prime lens, just choose 50mm as the focal length.

    It's because that online app already include the sensor size into the equation.

    Try this, choose a D700 camera and D90 with other settings stay the same, you will notice the results are different.
     
  3. Markw

    Markw No longer a newbie, moving up!

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    Alright. So with a 80-200 set at 200, and a 1.5x TC, I should put in 300mm...?

    Mark
     
  4. Josh66

    Josh66 Been spending a lot of time on here!

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    Yeah, use the numbers that are actually on the lens.
    (If it were any case other than that, it wouldn't ask you what camera you're using. It's automatically figuring in the crop factor.)

    edit
    Yeah, 200mm + 1.5 = 300mm.
     
  5. Markw

    Markw No longer a newbie, moving up!

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    Alright, thats alot to the pair of you. I am planning on going to the zoo here lately. This is why I asked.

    Thanks again.
    Mark
     

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