BASIC introduction to camera sensors
Sensors and Bunnies!
This is a BASIC intro to give people an idea about how the size of the little electronic thingy in their camera effects how they take pictures. A sensor, is the digital equivalent to a bit of chemical film in a film camera. it receives light from the lens and converts it into an image (OK, so there’s a LOT of software and hardware between sensor and image, but we’re gonna keep that in a black box because it doesn’t matter right now.) The lens on a camera collects light, and shines it into the camera. The same lens, will shine the same amount of light in the same way regardless of what camera its attached to.
So we have an image from a lens shining into your camera. Now take a moment, and think about a lens, what should be the first thing you notice? Glass, cost ITS ROUND!!! Your pictures on the other hand, are not… Your pictures are made up of only a portion of the round image of light that the lens shines into the camera.
Think now, about a rectangle placed inside of a circle. You can change that rectangle to all sorts of sizes and orientations, and as long as you stay inside the circle, you still get a pretty picture, but what picture you get changes based on what part of the circular image the rectangle covers.
Full frame (35mm equiv): This is a sensor the size of an old piece of 35mm film, combined with the lenses intended, it’s rectangle fills the circle to the edges, maximizing usable image space in the circle.
Crop factor: on many dSLRs you see what is called a crop factor. These represent sensors (and films) smaller than a full frame of 35mm film. (APS-C for instance, which is the Canon Rebel sensor size, is the same as the old Kodak Discman film size) These, when used with a full frame lens, “crop” the image as compared to the full frame camera, and result in using a narrower portion of the full image projected in the camera.
The above examples apply to dSLR cameras, and I start with these because that’s where we get our focal length math from. All our standardized lens measurements (50mm, 100mm, 24-70mm etc.) are based on the 35mm film size. When we get into point and shoot cameras, cell phones and others, we start using customized lenses for those cameras, and customized sensors to match. These take full advantage of the circle rectangle fit, but are (usually) necessarily smaller than even the smallest dSLR sensors to fit in the tiny camera bodies.
There will be more articles to follow on this topic, this is a version of a similar lesson I gave on Flickr.
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