tfttf554 – A Can Of Worms

posted in: Tips from the Top Floor | 6

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Scott wonders about kit lenses and primes, the podcast landscape changes and Simon opens a can of worms with his question on crop factor and depth of field.

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Workshops with Chris Marquardt
Feb 1-7 2015: Aurora Borealis, Iceland
May 2014: Mt. Everest
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  • http://twitter.com/Stavver_foto Jürgen Kaspar

    Hi Chris,

    your DOF lesson in this show is a little bit strange :-)
    the Nikon D700 with 12 MP got a larger DOF than the Nikon D800 with 36 MP? and the Leika S2 with 37 MP but larger Sensor will have the same DOF than the Nikon D700 because of the same pixel size? – I think NO, the size oif the pixel does not realy matter. Sensore size and appreture and distance to the subjekt are the factors that affect the DOF.

    what happens in the analog world, does a fine grain film will have more DOF than a film with larger grain?

    Regards
    Jürgen

  • twitch

    Chris, there is a simple, very simple, answer to your DOF question. Just multiply the focal length AND the aperture by the crop factor to get the 35mm equivalent.

    So shooting a 50mm f/1.8 on a micro four thirds body (2 times crop for simple maths) is the equivalent to shooting with a 100mm f/3.6 lens on a full frame body (and shooting at ISO100 on a this body is “equivalent” to shooting at ~ISO800 on a full frame body where the sensor tech is the same). 

    Sometimes in life there is simplicity in the complexity.

  • twitch

    and sometimes in life even simple maths can elude me; ISO100 on m4/3’s is like ISO400 on FF (2 stops), not ISO800. 

  • http://chrismarquardt.com/ chrismarquardt

    Not strange at all. If you keep all things the same, e.g. same distance, same lens, same aperture, and you only change the size of the sensor (e.g. swap out the D700 for the D800), then the actual measured depth of field (e.g. the distance from the first point of acceptable sharpness to the last point of acceptable sharpness) depends entirely on the size of the pixels (e.g. on the circle of least confusion that that sensor has), but you will have a different crop due to the crop sensor.

    If you change the distance to restore the size of your subject, that will change the DOF. 

    If you change the focal length to restore the size of your subject in the picture, that will change the DOF.

    I have elaborated more on this in ep556

  • http://chrismarquardt.com/ chrismarquardt

    I have elaborated more on this in ep556 btw.

  • Thomas Hender

    A little late to the party, but I just listened to this episode, and for the first time I actually understand the apparent difference in depth of field between cameras with different sensor sizes! I love the way you described it! Thanks, and please keep up the good work!