Why does my 24-105 have a different magnification (macro ratio) from a 105mm macro lens at same MFD?

Started Jul 28, 2022 | Questions thread
John Sheehy Forum Pro • Posts: 27,203
Re: Why does my 24-105 have a different magnification ... ?

bclaff wrote:

John Sheehy wrote:

Monicaa wrote:

My Panasonic 24-105 f4 has a MFD of 0.3m. It gives me a magnification of 0.5x at 105mm, which I have confirmed by taking photos of objects with a known size. This is 0.3m from the sensor plane to the object, with a working distance of about 10cm.

However, a 105mm macro lens with the same MFD (for example the Sigma 105mm 2.8 has a MFD of ~0.3m also), produces a 1.0x magnification.

How does this work? Two lenses at the same focal length and focal distance achieve different macro reproduction ratios?

Stated focal lengths are for infinity focus, and depending on the lens, the focal length may drop quite a bit at close focus. That's why max magnification needs to be stated as a lens spec.

How is this relevant? The focal length at minimum focus distance for both lenses is nearly identical at about 75mm.

How is the max magnification less relevant than stated focal length and MFD to the person looking for magnification?

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