Digital 101 Lesson 9

did you know that many if not most prosummer dslr cameras had a crop factor?  this is because their sensors are smaller than a full frame sensor which would equivalent in size to a 35mm negative.  the average camera has a "C" sensor that magnifies the focal length of the lens by 1.6.  the other popular sensor is the "H" that has a crop factor of 1.3.  what's it mean?  if you had a 50mm lens (considered normal on a 35mm film camera of full frame sensor) it would magnified by the crop factor of the type of camera that you were using.  a 50mm would become a 80mm with a C sensor.  this great for sports but becomes a little awkward in tight quarters.  another problem is the slowest shutter speed that you can safely use hand held before creating body movement.  the general rule is 1/the focal length of the lens.  1/FL  in the the case of the 50mm, 1/50 or 1/60.  jump to a 200mm telephoto and it becomes 1/200 or 1/250.  remember that crop factor?  the 50mm is a 80mm on a C or a 65mm on a H camera.  the 200mm now becomes either 320mm or a 260mm depending the camera and would require an increase in the shutter speed.  bottom line, the longer the lens, the faster the minimum shutter speed required without the aid of a tripod.