Turning the barrel of a 50-mm-focal-length lens on a manual-focus camera moves the lens closer to or farther from the sensor to focus on obj

Question

Turning the barrel of a 50-mm-focal-length lens on a manual-focus camera moves the lens closer to or farther from the sensor to focus on objects at different distances. The lens has a stated range of focus from 0.70 m infinity.
How far does the lens move between these two extremes?

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Cherry 3 years 2021-08-07T01:33:41+00:00 1 Answers 15 views 0

Answers ( )

  1. thugiang
    0
    2021-08-07T01:35:16+00:00
    Reply

    Answer:

    Explanation:

    To focus object at .7m , the image distance can be measured as follows

    object distance u = .7m

    focal length f = .05 m

    image distance v = ?

    from lens formula

    \frac{1}{v} -\frac{1}{u} = \frac{1}{f}

    \frac{1}{v} +\frac{1}{.7} = \frac{1}{.05}

    \frac{1}{v} =\frac{1}{.05} -\frac{1}{.7}

    v = .054 m

    = 54 mm

    when the object is at infinity , image is formed at focus ie at distance of

    50 mm .

    So lens position from sensor  where image is formed , varies from 54 mm to 50 mm .

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