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.

Published by

Matthew Duclos

A lens technician by trade, Matthew has spent his life servicing, refining, selling, manufacturing, and collecting cinema lenses from around the world.

7 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.

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