what is crop or crop factor?

Hi i've been reading the threads and found out people talking about crop factor and all, I was wondering, what is crop factor, I know cropping is cutting off a certain area, cropping the picture in the camera? is my Xti capable of this? thanks.

 

For many decades the 35mm format has dominated amateur photography, and people have gotten used to speaking of things in 35mm terms. Lenses are often described by their focal length; what people really want to describe is angle of view. Crop factor is how to figure out what focal length the smaller, APS-C digital format needs to get the same angle of view as a given focal length in 35mm format terms.

Example: If you have a crop factor of x1.6, and you want the angle of view a 28mm focal length lens provides for the 35mm format, you divide it by 1.6 to get the focal length that will give you the same angle of view for the smaller digital format. 28mm / 1.6 = 17.5mm. So an 18mm lens on a DSLR with a x1.6 crop factor gives approximately the same angle of view as a 28mm lens on a 35mm SLR.

 

35mm film was a series of little rectangles, each measuring 24x36mm. I'm sure you remember them. Now we shoot digital, so there's a sensor where the film used to be. A few cameras have full-size sensors (as large as the piece of film we all remember) but the vast majority of digital cameras have a sensor that's a little smaller. The crop factor means that some of the image (compared to what it would have been on film) is not getting captured. This is somewhat irrelevant in day-to-day shooting - what you see through your viefinder is what you're going to capture. Where it matters is in lenses. Because the 35mm film size and the related jargon had become a quasi-standard, the vast majority think of a 24mm lens as wide, a 50mm lens the middle of the road, and 100mm lens as being "long" - a telephoto lens. Especially if you like to shoot wide, the crop becomes something to be aware of. See Matt's description above.

 

i see, thanks for the reply guys.