# Lenses, Depth of Field, and Perspective

Started Jul 27, 2012 | Discussions thread
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Lenses, Depth of Field, and Perspective

I'm pretty new to interchangeable lenses, so I wanted to check to make sure I understand things correctly, and ask a few questions.

Let's say I am using a 50mm lens, standing 5 meters from my subject, and my subject fills the field of view. If I switch to a 100mm lens and still want the subject to fill the field of view, then would I have to stand at 10 meters away? Double the focal length and double the distance to achieve the same subject size.

Now consider the subject has some depth. If I set both my 50mm and 100mm lenses to the same aperture, then my depth of field will be exactly the same when focusing on my subject at 5 meters with the 50mm, and 10 meters with the 100mm, right? This is all based on fiddling with http://www.dofmaster.com/dofjs.html .

If both these lenses have the same maximum f-number, there is no way to increase the depth of field beyond what this maximum f-number can achieve, while still having my subject fill the frame, right? My only option would be to move further back so that the subject became smaller in the frame but had more depth in focus, and then crop in post.

Despite having the same depth of field and the same subject size with these two lenses at 5 meters and 10 meters, respectively, the final image would not look the same. The 50mm lens would cause objects near and far to appear further from the subject, while the 100mm lens would cause objects to all appear close together. Here is an example of what I mean, from Wikipedia:

How does this affect panoramas? If I capture an expansive vista with a wide-angle lens, will that shot appear to have much more distance between near and far objects than if I capture the exact same vista with a series of shots stitched together from a telephoto lens? Or does stitching a panorama together create the same feel as a wide-angle lens?