My digital camera does not have a full size sensor; can I still use the guide by multiplying the actual focal length of the lens by the cameras equivalent focal length factor?
No. The equivalent focal length factor (or multiplier) is based on the linear relationship between the size of a full 35mm frame and the camera’s image sensor. The formulas used to determine depth of field, however, are based on the exponential relationship of focal length to aperture size. Therefore multiplying the actual focal length by the camera’s equivalent focal length factor will not result in the correct answer for your camera.
