Reply To: My favorite local fauxtog

[nesgran]

A crop body does not change the focal length of a lens. It does not affect depth of field, regardless of what some defective DOF calculators may indicate. The reason little point & shoot cameras and cell phones have such deep depth of field is their lenses are very short. The apparent length of their lens is due to packing far more very small pixels onto their tiny sensors. They take “crop” to the extreme, making very short lenses seem long by cropping with a very, very small sensor. Look at the PowerShot ELPH 330 HS, for instance: 4.3 (W) – 43.0 (T) mm (35mm film equivalent: 24 (W) – 240 (T) mm). If they actually gave you a 240 mm lens, you could get very shallow DOF, but since they actually give you a maximum of 43 mm, you really have to work to get shallow DOF. Really, since they give somewhere between 36 and 50 mm, it should not be too hard to get shallow DOF if you could open it up enough, except the crop is such that you couldn’t get a person’s face in the frame when working at the distances you would use for 50 mm on an SLR.

In a way you are right but the effect of the smaller sensor is that the angle of view is smaller, hence lenses act as if they are longer. The result of this is that at the same equivalent focal length (i.e. effective angle of view) a crop lens will have a longer depth of field. That is why people say that a FF camera has a shallower DOF than a crop camera. Check the DOF requirements section