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Old September 26th, 2005, 04:01 PM   #1
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Not Pull Zooms?!?!?

Hello everybody,

I hope this is in the right section, sorry if it's not. Now, I know I keep going on about these a lot, and I'm really sorry for it. I'm going to try to stop after this.

I just contacted Canon USA for help about some of their EF lenses (through e-mail, not phone). I asked them if the EF 70-200mm f/2.8L USM, EF 100-400mm f/4.5L USM, and the discontinued EF 35-350mm f/3.5L USM lenses were push-pull zoom or not. (Or at least the kind that extends/telescopes outwards as the zoom is increased.). They said that no, none of these three are push-pull/telescoping zooms. Now, this is really flustering me, because I have SEEN the 35-350mm and 100-400mm lenses "telescoped". Canon said that they have zoom rings. Does this mean that the term push-pull refers to something other than the telescoping ability of the lens? Do these, or do they not, extend?

Thank you all bery much, and sorry for all these "newbie" questions!

~Clint Grant~
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Old September 26th, 2005, 06:17 PM   #2
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Clint,

Almost every zoom type lens I've seen for 35mm, extends and retracts for zooming. That is how they work, changing the distance between the internal individual lenses changes the focal distance.

The difference is that some change this distance by you physically pulling or extending the lens by hand and some use a ring to mechanically change the distance, gear or spline type drive.

In my experiance, which is extremely limited, the ones with the rings are the best and easiest to use. They will actually move out and then move back in as you zoom out. What I mean is that multiple lenses move and so maybe halfway zoom is the longest physical measured length of the lens, then as is zooms further it retracts and other lenses inside move to complete the zoom.

I know that I am not explaining this very well, but if you go to any camera store which has lenses, you will see what I mean.

Push-pull and ring are just rwo different ways of changing the physical relationship of the groundglass within the lense itself.

I hope this help and does not confuse you more.

Mike
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Old September 26th, 2005, 06:42 PM   #3
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Thank you very much.

Yes, this explained a lot. I had forgotten about the different ways of telescopic zooming. So, am I to assume that on Canon's website when it says "zooming: two-touch", that it extends, but then goes back inside itself, and when it says "two-touch push-pull" that it simply extends?

Thanks again, and sorry for the further questioning.

~Clint Grant~
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Old September 26th, 2005, 06:47 PM   #4
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I believe push-pull refers to a type of zoom lense which has a sleeve that slides over the length of the lense; you push/pull this sleeve front to back to zoom the lense, and rotate it to focus. I have a manual focus 70-200mm zoom of this type for my Minolta X-700 SLR (which would now be considered a rather old SLR). I don't know that push-pull is a very common design for zoom lenses anymore, as I would think it is not practical for autofocus lenses.
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Old September 26th, 2005, 07:50 PM   #5
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Old September 26th, 2005, 11:27 PM   #6
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Push pull means you slide the lens out like a trombone rather than twisting a mechanical ring to extend it, right? Otherwise i'm going crazy.

If that is the case, yes the 100-400mm is a push/pull. Canon seems to like the push/pull for their big zooms. I have a 100-300L that is also push/pull.
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Old September 27th, 2005, 01:24 AM   #7
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Neither of the 70-200 L lenses (both f/2.8 and f.4) are "push-pull" zooms. Both have conventional helical (twist) rings.
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Old September 27th, 2005, 07:24 AM   #8
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Quote:
Originally Posted by Dylan Couper
Push pull means you slide the lens out like a trombone rather than twisting a mechanical ring to extend it, right?
No, a push-pull lense does not extend as you zoom, at least not on the one I own.
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Old September 27th, 2005, 07:26 AM   #9
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Quote:
Originally Posted by Christopher Lefchik
No, a push-pull lense does not extend as you zoom, at least not on the one I own.

It all depends on the type and quality. Both of mine do extend.

Mike
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Old September 27th, 2005, 08:51 AM   #10
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Quote:
Originally Posted by Christopher Lefchik
No, a push-pull lense does not extend as you zoom, at least not on the one I own.
Both the 100-300 and 100-400 extend. Which lens do you own?

Are we all talking about the same thing?
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Old September 27th, 2005, 01:31 PM   #11
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Thanks again!

Thanks even more, everyone!

This is really clearing up a lot. Okay, so now I underdtand that the EF 70-200 f/2.8 DOES NOT extend AT ALL. That's the main thing I needed to clear up. This lens has a zoom ring, which has markings for zoom as you rotate it clockwise. The EF 100-400mm is literally pushed or pulled, and the markings are further along the barrel as you extend it more. Alright. I got it. Much clearer.

Thanks,

~Clint Grant~
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Old September 27th, 2005, 10:20 PM   #12
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Quote:
Originally Posted by Dylan Couper
Both the 100-300 and 100-400 extend. Which lens do you own?

Are we all talking about the same thing?
As I said, I own a Minolta X-700 SLR, which takes manual focus lenses. Thus, the lenses I have are all older, non-autofocus designs. The single zoom I have is a push-pull 70-200mm Auto-Promura (I know, you probably never heard of the company. Neither have I). This lense has a single, large rubberized sleeve that is pulled forwards and backwards along the length of the barrel to zoom, and rotated to focus. The lense does not extend while zooming

Push-pulls are also called one touch lenses, while lenses that have two rings, one for focus and one for zoom, are called two touch.

Doing some research, I see that the Canon EF 100-400mm has an interesting design which is a sort of hybrid of one touch (push-pull) and two touch zoom lense designs. It has a rotating ring for focus, and a push-pull mechanism for zooming.
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Old September 27th, 2005, 10:51 PM   #13
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Oops, missed that in your first post, my bad. Anyway, very interesting! You learn something every day.
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Old September 28th, 2005, 10:49 AM   #14
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Quote:
Originally Posted by Dylan Couper
Oops, missed that in your first post, my bad.
No biggie, I've done it, too.


Quote:
Originally Posted by Dylan Couper
Anyway, very interesting! You learn something every day.
You said it! The more I learn the more I realize how much I don't know. My great-grandfather said that you learn every day and you still die dumb.
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Old September 29th, 2005, 10:44 PM   #15
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I've got the 70-200 f2.8 IS and the 100-400L IS. The 70-200 employs a helical focusing mechanism, while the 100-400 is of the push-pull (think trombone) variety.

Both have their pros and cons.
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