Aperture/focusing distance changes at different FL for zoom lenses?

Started Mar 21, 2013 | Discussions thread
Dr_Jon Veteran Member • Posts: 5,110
Re: Aperture/focusing distance changes at different FL for zoom lenses?

Things worth noting...

Firstly the Minimum Focusing Distance is usually (always I think) quoted from the sensor, not the end of the lens, so if you do look up distances then remember that. For example I was amazed by the close focusing distance of the 12-35 f2.8 as I hadn't looked it up, actually it is just under 9" (from the sensor).

Secondly you possibly don't care. What you might actually care about is the Maximum Magnification, which says what is the largest size it can project something onto the sensor. For example if it is 0.2x that means at the closest focusing distance at some focal length it can project a 20mm high object as 4mm high on the sensor. On m43 that's about 1/3 of the image height. (So a lens with a MM of 0.2x and closest focusing of 50cm will enable a larger image of an object than a lens with 0.1x and 15cm. Also if the subject is alive it may be easier to take the photo as won't have to get so close.)

The aperture going down with focal length is how you keep lens size and cost down, both being important in lenses being sold to consumers.

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