Compression is Real

Started 11 months ago | Discussions thread
Great Bustard Forum Pro • Posts: 42,819
It is, but entirely due to position, not focal length.
6

JackM wrote:

The examples of "compression" (or, more appropriately, "perspective") below are due entirely to the position of the camera and positions of elements in the frame.  If one had used 100mm from the same position that the 400mm photo was taken from, the "compression" would have been the same, but the framing would have been 4x wider.

So, for sure, we can say that *for a given framing*, "compression" is a function of the focal length *for a given format*.

However, the problem with saying that "compression" is due to focal length without specifying both for a given framing and for a given format, is that people will incorrectly assume, for example, that a 50mm lens has a certain "compression" associated with it regardless of the sensor behind the lens (this same mistake is made with DOF as well).  And, to be clear, no, a 50mm lens on APS-C does not have the same "compression" as a 50mm lens on FF unless both photos are taken of the same scene from the same position, in which case they'll have a rather different framing.

In the end, it's much more simple to explain "compression" as the effect of perspective, and effect which is determined *entirely* by where the camera is located for a given scene, and the the framing is determined by the [equivalent] focal length for a given perspective.

100mm

164mm

271mm

312mm

400mm

Any questions?

Not a one.  You?

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