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Thread: Aperture vs focal length

  1. #1

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    Tom

    Aperture vs focal length

    I have a question which requires an urgent answer. If I am right then dof gets narrower at longer focal lengths. I am considering buying a 60 mm micro f2.8 but have been offered an 85mm f3.5 for a very good price. My question is would the extra focal length of the 85 give it an eqivalent dof to the 60 mm at f2.8. I want a macro lens but i want it to double as a nice portrait lens. Can anyone help please?

  2. #2

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    Re: Aperture vs focal length

    Give a man a fish, he eats for a day. Teach a man to fish...

    http://www.dofmaster.com/dofjs.html is what you need.

  3. #3
    PhotomanJohn's Avatar
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    Re: Aperture vs focal length

    Tom - DOF is a function of reproduction ratio. If you take the same photo with the 60mm and the 85mm at the same aperture (meaning that the subject is the same size in the frame in both photos) the depth of field will be the same. The only difference will be that the distance to the subject (working distance) will be greater with the 85mm giving you a slightly different perspective. Most of the time a greater working distance is an advantage for lighting the subject and other reasons.

    John

  4. #4
    Moderator Donald's Avatar
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    Re: Aperture vs focal length

    Quote Originally Posted by MrGladstone View Post
    I want a macro lens
    Tom - Others have provided answers to your question re DoF.

    But the other question is - How strongly felt is that statement above? If that's the priority, then you have your answer.

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