For reasons that I fail to understand the term “crop sensor” gets tossed around by people when referring to digital cameras with sensor sizes smaller than the traditional 24x36mm film standard, as if that was the Holy Grail of imaging. It’s not. The first Leica used the 24×36 format but others, including the Olympus Pen used 18x24mm and early Nikon, Minolta and other Japanese rangefinders adopted 24 x 32mm well before 24x36mm was in common usage.
Why 35mm? When Oscar Barnack developed the camera that came to be known as Leica, he wanted to use motion picture film sideways doubling it’s 18x24mm format to 24 x 36mm. One story about the 35mm motion picture film format, perhaps apocryphal but still interesting, was that when Thomas Edison was asked by his workers how wide to cut the film, he held up his thumb and forefinger and said “About this wide.”
What’s all this got to do with sensor size? Nikon’s D1 was introduced in 1999 with a 23.7 × 15.6mm sensor. When Canon introduced the D30 in 2000, the sensor size was 15.1 x 22.7mm. Even after Canon introduced a 24×36 mm EOS-1D in 2000, Nikon insisted 23.7 × 15.6mm was adequate and didn’t joint the ‘full-frame’ parade until 2007’s D3.
Olympus, much like Sony, was always willing to go their own way and introduced the Four-Thirds system at photokina 2002. I was there at the launch staring at a wooden prototype and listening to a German professor explaining why 18 mm × 13.5mm was the “perfect sensor size” for digital imaging. Nowadays, the Four-Thirds system is dead but lives on in sensors used by Micro Four-thirds system mirrorless cameras from both Olympus and Panasonic.
Some people, like my friend Jack, thinks the term “mirrorless camera” is synonymous with Micro Four-thirds but it’s not. Some mirrorless cameras use full-frame sensors, others use APS-C or 23.5 x 15.6mm format. Canon’s implementation of APS-C produces a 22.5 x 15mm sensor. For younger reader the Advanced Photo System was launched in 1996 and was a experiment in film formats but before it could catch on was quickly overtaken by digital capture. It had the advantage of using multi-format capture, including APS-C or 25.1 × 16.7 mm, which as you can see is not the same as what digital camera makers call this very same format.
What does “crop sensor” really mean and why should you even care. If film shooters can refer to roll film capture as 6×6, 6×7, and 6×9 and sheet film as 4×5, 5×7, and 8×10, why can’t we refer to the sensor size by its actual measurements because as you can see, their ain’t nothing standard about ”crop.”
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