Micro Four Thirds lenses and magnification factors

Started Apr 4, 2012 | Discussions thread
Klarno
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Re: Micro Four Thirds lenses and magnification factors
In reply to Freaklandian, Apr 5, 2012

All the "X" in a zoom lens means is: the longest focal length divided by the shortest focal length. A 3x zoom lens just means the longest focal length is three times the shortest focal length. It's a way of expressing how much a zoom lens zooms. The way it's used now, it's really just a number used by camera manufacturers to push compact sales to people who think big numbers must be better.

That has nothing to do with the magnification. Magnification is a function of focus distance and the actual physical focal length of the lens at that focus distance. Maximum magnification is listed separately on the spec sheet of a lens: the 14-42 has a maximum magnification of 0.19x. This means that the image produced by the lens will measure 0.19 times its actual size. Or, the size of the image as projected on the sensor for a 30mm object will be 5.7mm.

With a 1x (or 1:1) macro, this means the size of the image as projected on the sensor will be the same as the physical size of the object: a 10mm wide object will have an image 10mm wide. With a 2x, or 2:1 macro, a 10mm wide object will have an image 20mm wide. With a 0.5x, or 1:2 macro, a 10mm wide object will have an image 5mm wide.

All this only matters when you factor in the actual size of the format you're projecting on, as well: 35mm format is 36x24mm. Micro Four Thirds is 17.3x13mm. Since the image from a 4/3 camera will probably printed at the same size as the image from a 35mm format camera, one needs to compare how the image looks, rather than the number on the lens. A 0.5x (or 1:2) macro on a Micro Four Thirds camera will produce an image that looks more or less the same as a 1x (or 1:1) macro on a 35mm format camera.
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