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Author Topic: Any one ever seen a zoom extender  (Read 3415 times)

RGF

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Any one ever seen a zoom extender
« on: May 06, 2013, 11:35:04 AM »
Conceptionally the idea sounds great - an extender from 1 to 2 or even 1 to 1.4.

Would make the Great Whites even more versatile.

Suspect that no one has done this because the optical quality would be fair to poor (perhaps worse).

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Any one ever seen a zoom extender
« on: May 06, 2013, 11:35:04 AM »

robef

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Re: Any one ever seen a zoom extender
« Reply #1 on: May 06, 2013, 11:39:08 AM »

neuroanatomist

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Re: Any one ever seen a zoom extender
« Reply #2 on: May 06, 2013, 12:15:49 PM »
Em...no.

The OP is suggesting a zoom extender, i.e. twist a ring on the extender to zoom from a 1.4x to 2x.
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Re: Any one ever seen a zoom extender
« Reply #3 on: May 06, 2013, 01:52:37 PM »
I haven't seen one either.  I think you may be right about the issue with quality, extenders already show issues in lenses without adding their own.

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Re: Any one ever seen a zoom extender
« Reply #4 on: May 06, 2013, 02:53:20 PM »
Common place on ENG lenses, built in 2x.  Pretty horiffic results, combined with mf, fag paper thin dof, camera shake if you exhale anywhere near the camera.

Makes  2/3 lens very bulky, would make a 135 format lens massive.

Not a good idea.

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Re: Any one ever seen a zoom extender
« Reply #5 on: May 06, 2013, 04:36:04 PM »
But how about a 1.4 extender with a big bulb ( like the 200-400 with 1.4), and then the option to 'slide' in another 1.4 extender to give 1.96x ?

It will be really complicated and maybe impossible?, but i would be really interested:p

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Re: Any one ever seen a zoom extender
« Reply #6 on: May 06, 2013, 05:14:24 PM »
Years ago, I had a Vivitar extender that was coupled with a variable extension tube - it was quite useful for macro. I suppose you could say it allowed independent control of magnification.

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Re: Any one ever seen a zoom extender
« Reply #6 on: May 06, 2013, 05:14:24 PM »

Drizzt321

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Re: Any one ever seen a zoom extender
« Reply #7 on: May 06, 2013, 05:17:58 PM »
Years ago, I had a Vivitar extender that was coupled with a variable extension tube - it was quite useful for macro. I suppose you could say it allowed independent control of magnification.

That's different than what OP was referring to. An extension tube is, as you say, is good for macro photography. Not so good for increasing the focal length which is what OP was talking about. A variable extension tube is pretty simple, since extension tubes are basically just empty space (such as bellows), whereas tele-converters usually contain 1 or more lens elements to re-focus the image to get it to hit the focal plane correctly.
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RGF

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Re: Any one ever seen a zoom extender
« Reply #8 on: May 07, 2013, 12:12:49 AM »
Years ago, I had a Vivitar extender that was coupled with a variable extension tube - it was quite useful for macro. I suppose you could say it allowed independent control of magnification.

That's different than what OP was referring to. An extension tube is, as you say, is good for macro photography. Not so good for increasing the focal length which is what OP was talking about. A variable extension tube is pretty simple, since extension tubes are basically just empty space (such as bellows), whereas tele-converters usually contain 1 or more lens elements to re-focus the image to get it to hit the focal plane correctly.

Yea, a zoom Extender, TC - not an extension tube.  If not continuous, how about a stacked option - similar to the pending 200-400. Move a different power extender into position.  Perhaps 1.0, 1.2 and 1.4 options

From the lack of anyone have seen such a device I suspect that it optically very difficult at best

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Re: Any one ever seen a zoom extender
« Reply #9 on: May 07, 2013, 04:24:23 PM »
Years ago, I had a Vivitar extender that was coupled with a variable extension tube - it was quite useful for macro. I suppose you could say it allowed independent control of magnification.

That's different than what OP was referring to. An extension tube is, as you say, is good for macro photography. Not so good for increasing the focal length which is what OP was talking about. A variable extension tube is pretty simple, since extension tubes are basically just empty space (such as bellows), whereas tele-converters usually contain 1 or more lens elements to re-focus the image to get it to hit the focal plane correctly.

Yea, a zoom Extender, TC - not an extension tube.  If not continuous, how about a stacked option - similar to the pending 200-400. Move a different power extender into position.  Perhaps 1.0, 1.2 and 1.4 options

From the lack of anyone have seen such a device I suspect that it optically very difficult at best

Well, sure, you can stack TC's now, they just are different physical things. I imagine it'd be quite a bit more complicated to have one device that you introduce the different optics into position. More complicated mechanically, which introduces many more points of failure, and probably much more complicated optically unless it simply lifts one of the optics out of the way and puts another in it's place. Theoretically possible...but why? Just pull off the lens, and stack your TCs.
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RGF

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Re: Any one ever seen a zoom extender
« Reply #10 on: May 07, 2013, 07:25:19 PM »

Well, sure, you can stack TC's now, they just are different physical things. I imagine it'd be quite a bit more complicated to have one device that you introduce the different optics into position. More complicated mechanically, which introduces many more points of failure, and probably much more complicated optically unless it simply lifts one of the optics out of the way and puts another in it's place. Theoretically possible...but why? Just pull off the lens, and stack your TCs.

Why build a 1.4 into the 200-400?  Convenience?  Stacking TC takes time and are very discrete.  I would like to a zoom function to my 300, 400, 500 or 600 Great White

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Re: Any one ever seen a zoom extender
« Reply #11 on: May 07, 2013, 07:50:21 PM »

Well, sure, you can stack TC's now, they just are different physical things. I imagine it'd be quite a bit more complicated to have one device that you introduce the different optics into position. More complicated mechanically, which introduces many more points of failure, and probably much more complicated optically unless it simply lifts one of the optics out of the way and puts another in it's place. Theoretically possible...but why? Just pull off the lens, and stack your TCs.

Why build a 1.4 into the 200-400?  Convenience?  Stacking TC takes time and are very discrete.  I would like to a zoom function to my 300, 400, 500 or 600 Great White

And how much more are you willing to pay? And I'll be willing to bet they would need to do at least some revision of the optical formula since the tube would now be physically longer to accommodate the built-in TC. Or something. Anyway, personally I don't see why you would need to switch on the TC that quickly on your super-teles, but if you use them all the time maybe you have a use-case that would be useful to a large number of users.
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RGF

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Re: Any one ever seen a zoom extender
« Reply #12 on: May 07, 2013, 11:08:26 PM »

And how much more are you willing to pay? And I'll be willing to bet they would need to do at least some revision of the optical formula since the tube would now be physically longer to accommodate the built-in TC. Or something. Anyway, personally I don't see why you would need to switch on the TC that quickly on your super-teles, but if you use them all the time maybe you have a use-case that would be useful to a large number of users.

Here is an example - I have a 1.4 on my 500 and the bird, lion, lion chasing the impala, gets to close for the combo.  By the time I can get the extender off the camera, caps back on the extender, camera reattached to the lens, rebalance on the wimberley or raised to the roof of the safari vehicle, the action is over.  I may only have 30 seconds to the shot.  Same reason Canon puts a 1.4 in the 200-400, adds versatility

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Re: Any one ever seen a zoom extender
« Reply #12 on: May 07, 2013, 11:08:26 PM »

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Re: Any one ever seen a zoom extender
« Reply #13 on: May 09, 2013, 09:32:35 PM »
Conceptionally the idea sounds great - an extender from 1 to 2 or even 1 to 1.4.

Would make the Great Whites even more versatile.

Suspect that no one has done this because the optical quality would be fair to poor (perhaps worse).

Would you really want one? I have to figure that a zoom TC would incur a greater hit to IQ at all settings than a prime TC. A prime TC tends to have enough of an impact to IQ...

The idea certainly sounds intriguing, but I think a zoom lens is more practical from an IQ standpoint.
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Re: Any one ever seen a zoom extender
« Reply #14 on: May 10, 2013, 05:22:53 AM »
Interesting ... I never heard of a zoom extender before, but it would be neat idea if they do produce a good quality zoom extender.
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Re: Any one ever seen a zoom extender
« Reply #14 on: May 10, 2013, 05:22:53 AM »