Compression is Real

Started 7 months ago | Discussions thread
Mike CH Veteran Member • Posts: 9,631
Re: Longer lens *or* cropping

Donald B wrote:

Mike CH wrote:

kiwi2 wrote:

Mike CH wrote:

Donald B wrote:

You have displayed in the images that the background looks closer to the team using longer focal lenghts.

No, he has shown that when he moves backwards and forwards the proportions between foreground and background changes. The lens and its focal length is only responsible for maintaining framing, i.e. size of the foreground subject.

The proof is easy.

In the position where the 400mm shot was taken, also take a 100mm shot. Crop that last shot to the size of the 400mm shot. You will now see that the cropped image show exactly the same "compression" as the 400mm image.

So you cannot keep the foreground subject taking up the same area of the frame at the longer distance with the shorter 100mm focal length.

Of course you can’t, if you have moved away from the foreground.

You need the longer 400mm focal length for it to work.

Or you crop. The effect on the so-called “compression” is identical. You loose resolution, yes, but the ‘“compression” is identical.

Regards, Mike

Cant remember. Does the dof stay the same as well ?

Absent effects from loss of resolution, I'd say yes.

FingerPainter is correct, DoF changes due to the magnification.

Loss of resolution is of course the reason why you’d rather use the longer lens than crop in real life.

Regards, Mike

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