Quote Originally Posted by Cris View Post
Ok. i am now confused, surely you don't have to factor in crop factor when using this rule, The lens is still the same focal length lens regardless of what sensor it sits in front of, the only thing that changes is the field of view- from the sensor. So why would you need to factor in any adjustment because you are using a smaller sensor. The rules of physics surely don't change just because you are using a smaller sensor. Does someone who uses a D810, which I think has an option to shoot in dx mode all of a sudden have to increase their minimum shutter speed whilst still using the same lens. Seems odd, still the same sensor, just using less of it.
Yes you do. The FL is always the same, but the image area is smaller thus any movement is more obvious (needs a diagram) -- but believe me it is needed to be accounted for (basic geometry)