Friday, 9 March 2018

crop factor - Why are 35mm image sensors the standard?


I often hear about sensors being full frame (which I think means 35mm sized) and others being cropped (if they are less than that) such as APS-C sized sensors.


My question is what is so special about the size 35mm? Why is it used as the standard against which everything else is measured? Is it the largest sensor possible or does it have some other characteristic that makes it stand out?



Answer



For digital cameras, it's purely due to historical reasons - 35mm was the dominant size for film cameras and cinematography. As for why film cameras ended up with 35mm, I'd suggest 35 mm film and 135 film on Wikipedia as a good place to start. It's also worth noting that "35mm" is not actually the size of the image, which is 36x24 mm, but the width of the film.


It's certainly not the largest sensor available - a number of companies (Hasselblad, Phase One, Pentax) make "medium format" sensors which are larger than 35mm sensors.


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