A 50 is a 50 is a 50!

When I was younger, I remember hearing the phrase “a 50 is a 50 is a 50”. A phrase coined by Denny Clairmont and carried on by my father. This was in regards to people using 35mm format lenses on a 16mm format camera. Denny or my father would scold people for saying that a particular focal length is multiplied when used on a smaller format. This is simply inaccurate. Unfortunately this mistake has become even more common today with popular formats such as Super 35 or APS-C. These are considered “crop sensors” when compared to 35mm Full Frame and only utilize a portion of the intended image circle created by a Full Frame lens. The only thing that changes when using a 35mm FF lens on a Super35/APS-C sensor is the field of view (FOV) or the angle of view. So unless you’ve spent the past 30 years memorizing the field of view associated with a specific focal length, strictly on 35mm Full Frame, don’t bother trying to compensate for crop factor.

9 thoughts on “A 50 is a 50 is a 50!

  1. Didn’t you forget to talk about Depth Of Field (DOF)? DOF is directly related to sensor size. A lens of Xmm focal length will produce different DOF on a FF sensor than on a APS-C sensor.

    Between the DOF and the FOV, a 50 looks a lot different depending on which camera it’s on.

    1. Nope. Didn’t forget. I just didn’t care for this particular post. The point of this post was to get the “crop factor” point across. Yes, DOF is very important and directly related to image circle and sensor size, but when it comes to people trying to figure out how a lens will “look” on a specific camera, nobody ever asks how the depth of field will change when using a 50mm on a Super 35mm sensor as apposed to a 35mm full fame sensor. But thanks for the comment.

      1. I’ll ask, as I am wondering about that question. How will the depth of field change when using a 50mm on a Super 35mm sensor as apposed to a 35mm full fame sensor. Thanks.

  2. You don’t need to “memorize” the field of view to have a feel for how a certain focal length looks on a given type of camera. Photographers who switch between systems have known for years that 50mm is a “Wide Angle” lens on a Medium Format camera, a “Normal” lens on a “Full Frame” 35mm camera, and a “Telephoto” lens on a crop sensor Micro Four Thirds camera. In this regard it’s silly to just say “A 50 is a 50 is a 50” because unless you know what format it you are working with, you don’t know if that 50 is wide, normal, or telephoto.
    You couldn’t shoot a 50mm Micro Four Thirds lens on a Medium Format camera, it doesn’t have sufficient circle of light to cover the film or sensor. A 50mm Medium Format lens is a VERY different beast than a 50mm 16mm motion picture camera lens!

    It is not a mistake or inaccurate at all to say that a 50mm lens on a Micro Four Thirds camera has a “35mm equivalent focal length of 100mm”. In fact most lens manufacturers such as Canon and Nikon routinely list in the specs the “35mm equivalent” focal lengths of their lenses when used on APS-C cameras. If they don’t list it, these are easily calculated using the “crop factor”.
    For instance, a Micro Four Thirds camera has a “crop factor” of 2. Therefor a 50mm f/2 lens on a Micro Four Thirds camera has a “35mm Equivalent” focal length and depth of field of 100mm f/4. All this means is that it behaves like a 100mm f/4 lens in terms of focal length and depth of field.
    That wasn”t so hard now, was it?

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