Over in the Digital Photography Review Forums, some people are badmouthing the Nikon D200 camera because it’s not full frame. What they mean is that, like most Digital SLR cameras, the sensor isn’t as large as the standard 35mm frame size used in a film camera. I’ve only been learning about photogaphy for about a year, but I’m pretty sure that although this is true, it’s also a bit of misdirection.
What’s true is that the digital image sensor is indeed about 2/3 the size of a 35mm frame. It’s also true that if the sensor was as large as a 35mm frame, it would produce better images. A 35mm frame is 50% larger in each dimension, meaning a sensor that size could capture twice as many pixels. Or, and this would be my preference, it could have the same number of pixels, each with twice the light-gathering area, giving an extra stop of sensitivity for the same noise level. (That is, not more pixels, but better pixels.) The thing is, however, there’s nothing magically wonderful about the 35mm frame size. When it comes to the imaging quality of digital sensors, bigger is always better.
The same is true of film. In fact, 35mm film is the rock-bottom film size that is considered suitable for professional use. (If you know what APS, 110, 126, and 8x11mm films are, congratulations, but those have never been used professionally and are respectively dying, nearly dead, dead, and used only by spies.) Photographers who want really nice images don’t use 35mm, they use one of the medium format sizes built on a strip of film 6cm wide. Photographers who want better images use 4×5 inch film sheets. For even better images they can use 5×7 inch film. Or if that’s not good enough, there’s 8×10 inch film. And if that’s not good enough, there are even larger specialty film sizes.
I’ve heard that the 35mm format was chosen because the same format is used in 35mm movie film, so it was being produced in large amounts which made it cheap. Even if that’s not true, the 35mm format is simply an engineering compromise between image quality, camera size, and cost. Digital imaging sensors are designed with the same sort of tradeoffs, but being a different technology, they’ve settled around a different common size.
The point is, there’s nothing special about the 35mm film size.
Update: Well, the one thing 35mm has going for it is that every camera maker has a lot of lenses that work with 35mm. Then again, those lenses will also work with smaller formats as well, including all Digital SLR sensor sizes. Still, the 35mm format is the largest format that will work with readily available consumer lenses.
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