followup to Franks question on Osprey size.

Discussion in 'General Technical Discussion' started by Greg, May 27, 2005.

  1. Greg


    Apr 5, 2005
    Fayetteville, TN
    I know certain lenses can determine distance and report that to the camera in calculating flash information. Is that data recoverable after the shot?

    I'd like this information to calculate the size of objects in the image given no other reference is available in the frame. THis can be done with the following simple equation.

    distance / focal length in inches = scale of image in feet per inch

    Given the D2H sensor is .9 inches

    sample calculation
    an object is 75 feet away with an 11.81 inch (300mm) lens
    75 / 11.81 = 6.3 feet per inch at the sensor.

    since the sensor is .9 inches divide the 6.3 by .9 to get the total space covered on the sensor which in this case will be 7 feet.

    if an object goes across half the frame then that object will be 3.5 feet.

    or you could temporaily set your image size to a width of 7 and read the size directly off the ruler.
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