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While browsing for cheap second hand lenses I found the Cosina 70-210mm f4.5-5.6. The seller notes that it's a pump zoom. Googling the term does yield some results, but these simply state that a certain lens is a pump zoom lens, without going into the details. I only found out that these lenses have the focus and zoom control somehow combined in one pumping control (right?).

What is a pump zoom lens? How do you operate it? Are there any (dis)advantages compared to a regular zoom lens with a ring?

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  • So why the down vote? Is the question lacking research?
    – Saaru Lindestøkke
    Oct 22 '14 at 11:40
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It just means you push / pull the front of the lens to zoom, rather than twisting a zoom ring.

The mechanism is simpler to design/manufacturer but is less precise and has a reputation for sucking dust into the lens due to the large change in volume when zooming.

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  • And manual focussing is done in a similar fashion? Or is there a separate control for that?
    – Saaru Lindestøkke
    Oct 20 '14 at 17:36
  • @BartArondson - One would normally turn the ring to focus; there's only one gripping surface which is both the focus ring and the push-pull grip for the zoom operation. When you're working manually, it's a little faster (if less precise) to kill two birds with one stone, as it were.
    – user32334
    Oct 20 '14 at 17:40
  • @user32334 it depends on the lens. I own a Canon EF 100-400 lens, and it has a separate rubber area for zooming (which doesn't turn) and a focus ring (which does turn, but the grip has lines in the turn direction, not in the zoom direction, so it's not good for zooming). It also has a friction ring that you can use to tighten (or lock) the zoom mechanism so it doesn't extend by itself.
    – Erwin Bolwidt
    Oct 21 '14 at 13:02
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Here is an example image of a 'pump zoom', this is the Canon 100-400mm IS USM:

http://www.juzaphoto.com/shared_files/articles/articles_no_update/canon_100-400-large.jpg

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  • I don't see how this answers my question.
    – Saaru Lindestøkke
    Oct 21 '14 at 10:24
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    The front side of the lens "pumps out" while zooming in. It's the same lens, first at 100mm and then at 400mm.
    – Rodrigo
    Oct 21 '14 at 13:12
  • @BartArondson That's odd, I always felt that a picture is worth a thousand words, and this one shows particularly clearly the 'pump action'. Consider it an augmentation of Matt Grum's answer.
    – TripleAntigen
    Oct 22 '14 at 12:00
  • It's clear that a zoom lens gets longer when it increases the focal length, but from the picture it's not clear how you operate it. The extension could've been the result of any action (on of which is pulling the front). I was not interested in how one looks (I already found the Cosina 70-210mm online), but I was interested in its operation. I added this to my question.
    – Saaru Lindestøkke
    Oct 22 '14 at 12:06
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The action of zooming the lens is nearly identical to the action of reloading a pump-action shotgun: slide the barrel forward and backward.

Back in the days before autofocus this was the preferred zoom lens mechanism. The two-ring lenses required you to move your hand between the zoom ring and the focus ring which took time. Some preferred the precision of two separate rings (landscape, studio etc., anywhere the subject isn't moving) but wildlife and sport photographers wanted the faster action of the push-pull-turn design. So if you are only buying one (quite expensive) lens for general-purpose use the pump-action was more versatile.

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