Focal length help

chump1979

chump1979

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if you have a 70-200 lens on a 40d with it's crop factor of 1.6 - does this mean that the maximum focal length is 320mm (35mm equiv)?

And then what if I add a 1.4 TC? 448mm??? :shrug:
 
No change in focal length but the crop factor will give a smaller field of view there is no increase in magnification
 
What he said ^
 
Just a little point to add, I use my old film camera lenses on my 20D, the cropping causes me no end of problems as I cant seem to get in close to nice shots, I have to stand way back. I'm going to get some lenses designed for the camera.
 
in 35mm equivalent terms you are correct. Yes the field of view is smaller, hence when printed at the same size, it is as though the lens was longer. This is why compacts usually site 35mm equiv - a 66mm lens on a 1/1.8" Fuji is 300mm equiv, for example.
 
The focal length of the lens doesn't change just because you put it on a camera with a crop factor sensor. What actually happens is that the sensor "see's through" a smaller area of the lens, therefore giving an effectively larger focal length. If you shoot the same sparrow with the same lens on a crop and ff sensor camera, the size of the bird in the frame will not alter but you will get more scenery around the bird in the shot from the ff body as the sensor is "seeing through" all of the lens whereas the crop sensor camera "see's through" a smaller area of the lens.

Phew! HTH :)
 
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