When it comes to image sensors, the part of your digital camera that collects image data and creates the picture, bigger really is better . Not only does the sensor size make a difference in image quality, clarity, and noise, it also changes the way lenses work.
A full frame image sensor is the same size as a frame of 35mm film, so it behaves normally when getting data through a 35mm camera lens. DSLRs with smaller sensors have to employ a “crop factor” when using those lenses, which means that the images they capture... well, it’s easier to see the difference than to explain it.
Using various lenses—20mm, 28mm, 35mm, 50mm, 85mm, 100mm and a Lens Baby Composer —photographer Mike Collins demonstrates exactly how much of the field the two sensors can “see.” And no matter which lens is employed, the video’s side-by-side comparisons make the 7D’s crop factor quite obvious.
Will you be checking the sensor size on your next DSLR purchase?