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Stacking Teleconverters

Author: BELFAST4 <[email protected]>
Date: 1999/10/04
Source: Share Your Pictures Club

Well done & well written. I've used teleconverters in the past. An inexpensive way to lengthen your focal length.
Dennis

Author: philfflash <[email protected]>
Date: 1999/10/05
Source: Usenet

Great article. If nothing else you should post your set-up whenever someone claims the Rebel is too weak to hold long lenses. I remember there was a man in Berkley Calif. Who made 3000mm and longer lenses starting from fairly long telephotos. He stacked extenders as you do. He had some fantastic pix of S.F. Bay. Pelicans in the fog, etc. keep up the good work! BTW my next purchace is going to be another teleconverter!

Author: Banjopikr1 <[email protected]>
Date: 1999/10/05
Source: Usenet

Good article. I never thought to change the positions of the converters to see if it made images better. You have opened my eyes!

Ken

Author: Earl Fieldman <[email protected]>
Date: 1999/10/05
Source: Usenet

Well, there are stacks and there are stacks.

I've been experimenting with 2x tcs, all of:
TC-301
TC-200
Vivitar 2x-3

I have 3 of each, and a Nikon AF300/f4. The 301's are worth about $300 each, the 200's about $100 each, and the Vivitars about $25 each.

Here's the ballpark:
The natural light limit is around a stack of 7 2x TC's deep. (the tallest stack I can make from my collection). This requires bright sunlight, a reflective subject, and a "pre-focused" setup. It is barely visible at all. After that, it's all dark. Some would say this limit is more like 5 or 6, but I can find the subject and focus successfully in most bright sunlight situations using a 5 deep stack. With 6, one's first impression is that it is completely dark, but effort yields an identifiable subject.

At least for the Nikkor AF300/f4, the TC-301 is of no obvious improvement over a $25 Vivitar when stacking. Worse, you cannot stack TC 301's; you can use only one. Irritating, they're about 4 times as long as a Vivitar (the TC-200 is nearly twice as long as a Vivitar). I was disappointed in the TC-301.. although I concluded that they hadn't designed it for what I was doing, and if evaluated for its intended purpose, it woould probably fare better.

I have photos taken with a 6 deep stack; you would not consider them successful, although the subject is readily identifiable. I've not given up, however. There are problems keeping the setup still. You've heard that you need a tripod for a 300mm lens? Well, you need more than a tripod for a somewhat flexible 300mm *2^6 lens (300*64, or 19,200mm) lens. About 385 "power". You need even more than two tripods.

And there you have it,
Earl F.

Author: philfflash <[email protected]>
Date: 1999/10/06
Source: Usenet

There were some tricks in the article I read about the man in Berkeley and here are those I remember (BTW the article was in Pop, Modern, or Petersen's sometime in the late 1970s)

The two by four (this works; I do it with my baseball bat 500 and it's 2x) Instead of a tripod he used a 2x4 board with holes drilled and 4x20 bolts in the appropriate places. The lens and camera were tightly bolted down and I believe he used a few foam supports under the tele- converters. I have also built a smaller on of these, 1x4 to use under my 75-300 zoom with a teleconverter. This one mounts to my tripid. With the board system attached to his porch by bungies and other chunks of wood he was able to angle down to the bay. He also used the roof rack on his car, setting angles again with wood blocks, a pair of step ladders (or perhaps saw horses) staked to the ground with tent pegs, and any trees, buildings etc he could get permission to tie onto.

The part I've never tried was the sapotting scope. He had it mounted to the board with adjustable stand-offs. By first using a relatively short lens on the camera (attached to the board) he would set up his shot. The next step would be to line up the spotting scope with the adjustments in the stand-offs. He then would put in the long lens and wait, watching through the spotting scope, for something to happen. There was a islet, little more than a rock at high tide where the pelicans gathered. The picture of a flock of pelicans, some sitting, some waving their wings, in the blue mist was quite amazing.

I think the young fellow who wrote the artical on his web site deserves a big hand of applause for his experiments and his photographs. We need more rule breakers. They are the ones who will advance photography.

Have you tried reversing a teleconverter? I'm sure it changes the magnification, but does it widen the field of view, or is that limited by the shape of the front lens?

What happens with just a teleconverter on the camera?

Cole Petersburg
Sat, 2 Mar 2002 17:52:02 -0600 (CST)

I find it funny how you say it's all about the math when if you add up the amounts of money spent it totals $1059.90 not $969.80 as stated in the article. Better go back to elementary school.

Mike
Sun Feb 20 15:23:06 PST 2005

You are right. Thanks for the heads-up. I'll correct it. Good thing we have people who went to elementry school checking over my writings. ;-)

Chieh Cheng
Mon Feb 21 11:32:26 PST 2005

A better comparison to your lens would be the Quantaray 600-1000 f9.9-16 lens - it's only $350.

john
Sat, 4 Feb 2006 17:08:25 -0800

"Some photographers feel that they can get away from using teleconverters because they can simply move closer to their subject"

But if you are photographing the moon, then implementing this suggestion would tax the resources of even the most enthusiastic amateur photographer! :-)

Martin
Thu, 16 Feb 2006 04:58:13 -0800

My experience is, using a 1.4x Teleconverter, even a cheap one, produces little or no noticable degradation when used with most any good lens that can handle a teleconverter. That includes using one not made by Canon, despite what may be suggested by Canon. Using the 2X, autofocus will not always lock and manual focus is suggested to help assure you are not disappointed later. I question stacking converters, but I suppose it would be no worse than using a telescope.

Steve
Sat, 13 Jan 2007 07:37:20 -0800

There is a huge problem using converter: you increase the size of sharpness of your initial lens (and previous converter if you have it).

With a perfect converter 2x you increase by 4 the surface of smallest blurring so if your lens is only quite good, you will just increase the size, but not the resolution of your images.

And as teleconverter are not perfect, you add deformation and blur.

Exercice:Let imagine your using a canon rebel, so pixel size is 7.5*7.5micron2 with the a beautiful lens with resolution above this size, let say 5microns. You will indeed increase resolution with the 1.4x, but after, you will only increase size, not resolution...

so adding teleconverter is not the good way to obtain really long focal, it's better to take mirror lens for instance (found mine about 100$ for 500-800 9/11 on ebay).

For inversing the teleconverter, if it would be possible mechanically for the focus, you would obtained the image smaller with black ring around.

seb
Tue, 10 Jul 2007 11:28:47 -0500

I've spent the past week buying a LOT of cheap Pentax teleconverters off eBay. With those and a 70-205 Hoya lens on the end, I should have a nice little telescope...

To get rid of chromatic abberation, I plan on sticking a colour filter on the end (either from my stage-lighting, or a pair of holographic notch filters in periscope arrangement). This means much longer exposure times, but far less aberration since only a narrow colour band will pass into the lens.

If this works out, I'll adapt the stack for use with my Nikon DSLR and upload the results (after some intense deconvolution to sharpen them a bit).

If anyone is interested in this little telescope project, or has any advice, my email address is [email protected]

Mark Cowan
Mon, 26 Mar 2012 21:55:40 +0400

That's a very interesting project, Mark. What is your photographic subject for this setup?

Chieh Cheng
Tue, 27 Mar 2012 00:38:17 +0400

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Title: teleconverter for Vivitar 70-210mm
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Excerpt: HI, your "Stacking Teleconverters" write-up was pretty enlightening..... I am looking for a 2x TC for my VIVITAR 70-210mm zoom lens.....Could you help me choose one please....!!!
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Excerpt: I came to this site to find what others thought of Quantaray 2X AF Teleconverter, and this [page] gave me that info. Thank you. One big question though, I've been told that the glass in this teleconverter was junk, what do you think of it?
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