2. In Digital SLR Sensors Size Really Does Matter

• EOS 5D Digital SLR...
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• • shopkingcamera
  • $1589.95

So what's the big deal with full size sensors?

First, the larger the sensor the more room there is for pixels. Camera designers can use this space for more and larger, less tightly packed pixels. More pixels mean higher resolution and larger pixels with more space between them mean less noise. All of this means bigger enlargements or more cropping flexibility when you print your photos.

Second, lenses produce circular images. Read along and follow the diagram below. If a camera has a full frame (35mm-film size) rectangular sensor, it can capture the full image from a lens designed for 35mm film. A smaller sensor with the same lens can captures only part of the full image. This results in what is called a sensor's "magnification factor." Most truly professional digital SLRs without full frame sensors have a magnification factor of 1.5x (Nikon) or 1.6x (Canon). So for example a 50mm focal length lens made for a 35mm film camera acts in terms of magnification as a 75mm (1.5x) or 80mm (1.6x) lens on a sub full frame digital SLR. For the record, a full frame digital SLR has a magnification factor of 1.0x, the same magnification factor as for a 35mm film camera.

A full size 35mm sensor captures all or almost all of a rectangle within the image circle produced by a lens designed for a 35mm film camera. A smaller sensor captures only a portion of the rectangle within the image circle, resulting in a magnifying effect.

Some photographers love the magnification factor because it allows lower focal length lenses to masquerade as higher powered telephoto lenses. But it is, after all, just a masquerade because the lens's focal length is still 50mm even though the magnification factor makes it seem like an 80mm lens. Lenses in the 80mm - 100mm range are great for taking portraits because they provide a nice perspective for photos of the human face and have limited depth of field which causes backgrounds to be attractively thrown out of focus. However, the perspective and depth of field of our lens is that of a 50mm not an 80mm lens. So when you use a 50mm lens at a 1.6x magnification you get a very different perspective and sharper backgrounds, both of which are less suited to portrait photography, than you would with a real 80mm lens.