FF equivalent focal length factor of lenses using 1:1 aspect ratio

Discussion in 'The Watering Hole' started by RDM, Feb 23, 2014.

  1. RDM

    RDM Mu-43 All-Pro

    Hey, I was wondering something & do not have the energy right now to do the math on it so I was hoping someone would like to figure out and answer this for me.
    I know that the FF equivalent focal length for lenses when using them on µ4/3 cameras is x2, based on the diagonal angle of view. But what is the equivalent focal length factor of lenses using 1:1 aspect ratio, and what is it using 1:1 on a GH2, which has a longer diagonal in 1:1 mode due to its multi-aspect sensor.?

    Thank you in advance.
  2. dhazeghi

    dhazeghi Mu-43 Hall of Famer Subscribing Member

    Aug 6, 2010
    San Jose, CA
    The GH2's multi-aspect sensor only supports 4:3, 3:2 and 16:9 natively. 1:1 is just a crop of 4:3. It gives you roughly a 2.35x crop factor (diagonal of 18.4mm vs. 43.3mm on FF).
  3. Amin Sabet

    Amin Sabet Administrator

    Apr 10, 2009
    Boston, MA (USA)
    I'm not sure exactly what you are asking here. Dara has given you the crop factor for 1:1 on 4/3 compared with 3:2 on FF, using the diagonals of each as the means of comparison (crop factor can also be calculated based on format area, which will give a slightly different answer (more info here).

    The crop factor of 1:1 on 4/3 compared with 1:1 on FF is approximately 1.85x (based on full frame size of 24x24mm and 4:3 size of 13x13mm).
  4. RDM

    RDM Mu-43 All-Pro

    Yea that's it .. thanks, that is what I wanted to know ..
    Didn't feel like thinking, I been sick in bed today ;)

    Don't worry, Dara understood the question I asked and gave me the answer.
    Thank you for all the extra info & for trying to help

    So roughly a 2.35x crop factor. Nice!.
    So that makes my 20-80mm c-mount equivalent to a 47 - 188mm
    and my 12.5-105mm lens roughly equivalent to a 29.38 - 246.75mm