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Originally Posted by KingZee
Dude that's by far the best explanation I've had. Things are making sense now. 
I fully understand why at its lowest point it crops by 1.5 causing a 10mm to be 15mm but how does it amplify when a lense is closed all the way? Like how does a 200mm become a 300mm? Don't know if that question makes sense? Also, does that still mean that you're going to get the same sharpness you would from a 200mm full frame and 200mm (300mm) crop frame? |
Thanks again.
Makes perfect sense (your question).
I believe you are meaning Zoomed in all the way instead of closed all the way, which would be refering to the aperture (blades inside the lens which control depth of field), which is essentially how much is in focus from the focus point from front to back. More on that later though.
The lens does not actually "Become" a 300mm lens just because you use it on a smaller sensor, it's still a 200mm lens. All you are seeing through the viewfinder however is a cropped area of what a full frame sensor would be seeing through that same lens at 200mm, which in turn becomes the equivalent of a 300mm lens on full frame. You would have to crop the image if shot on full frame to get the same image on both cameras from the same disatance at the same focal length.
Sharpness all depends on the lens. If you are using a 200mm lens on a full frame and a 200mm (300mm "appearance" when compared to FF) on crop, you will get a closer shot of whatever you are shooting while still using all 12 megapixels on the crop sensor, whereas you would have to crop the image of the full frame cameras shot to get the same photo, therefore reducing the total megapixels when cropping. You would have to use a 300mm lens to get the same shot from the same distance as the crop sensor of shooting full frame. I'm saying a lot of stuff over and over but hopefully it aids in understanding of all this jibberish