I shoot my outdoor sports with a 200mm 2.0 prime and looking at getting a 400mm 2.8. Is there a way to crop a photo shot w/ the 200mm to what it would have been if shot with the 400mm? I want to see the difference for this field of view.
Hi Tom, Thanks for taking time to share this. The table show the fov for the 200mm at 10.3 and the 400mm at 5.2. So would it be correct to crop this to 1/2 of its size, the frame is 10.933 high, so cropping it to 5.466 would be the fov for the 400? This makes sense to me per the numbers- everything is magnified by 2, but I want to make sure I am not overlooking something.
Not to be a nit-picker, but to pick nits anyway, the crops don't work the same way as a change in focal length. They sort of do, but to explain it better would require examples that I don't have access to at the moment. To try to explain: Cropping alters the area the image shows. Changing the focal length of a lens changes the perspective in addition to changing that area. Imagine "zooming-in" from wide-angle to telephoto versus simply cropping a wide-angle shot. The lens renders the images very differently. In the focal lengths being discussed, all telephoto, the perspective doesn't change as much as going from wide-angle to telephoto, but it still changes.
This topic is probably worth a much more in-depth discussion, and I'm sure it has been covered elsewhere. Maybe our Nikonian editors could take this up.
>Only altering the camera-subject distance changes >perspective.
When people write about the different perspectives you get from different focal lengths, there is an assumption that you will have moved to get the same framing of the subject with each focal length. Unfortunately, this assumption is often unspoken and thus the reader gets the wrong idea.
For anyone who has never done so, it's instructive to take the same shot, from the same location, using a short lens and a long lens. Then take the short-lens shot and crop it to the same field-of-view as the long-lens shot. You'll get the same image other than for differences due to lens aberrations and image resolution. Seriously, try it if you have never done it.