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Old May 27, 2005, 2:40 PM   #1
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Ok, I am finding that I don't have quite enough reach for some of the things I'd like to photograph. Most of the photos would be in full daylight, so I can afford to lose a few stops. I currently have a Canon EF 70-200mm f/2.8 L IS and a Canon EF 1.4x II teleconverter. With the 1.6x crop factor of the 20D, I have a effective reach of 448mm @ f/4.0.
I am wondering if I should get an EF 2.0x II teleconverter which will get me to 640mm @ f/5.6. I am also wondering if the 2 teleconverters can be stacked for a reach of 896mm @ f/8?
If this would work, it seems the least expensive way to go, as long as I have enough light for f/8 and want to manually focus.
I am not against going with a Sigma solution, but I get a large discount on Canon product, so would like to explore those options first...


Thanks for any help,

mactek
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Old May 27, 2005, 3:08 PM   #2
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mactek wrote:
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I am also wondering if the 2 teleconverters can be stacked for a reach of 896mm @ f/8?
If this would work, it seems the least expensive way to go, as long as I have enough light for f/8 and want to manually focus.
You can but the picture will not be very exceptional... CA will start to crop first
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Old May 27, 2005, 4:43 PM   #3
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I was going to suggest the Sigma 50-500. It is a very capable (if slow) lens 'cause the max aperture is f6.3 (it reports f5.6 to the camera so AF still works.) And the price isn't bad.

The 100-400 is a good lens for what it is, and with your discount all the better. It is a fun hand-holding lens too.

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Old May 30, 2005, 11:32 AM   #4
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Thanks for the responses. Anyone else have suggestions?
I've also wondered about attaching something like an ETX-90 scope. It's 1250mm f/13.8. I could probably find it cheap on the used market. I'd obviously need lots of light to shoot terrestrial objects...

Anyone?

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Old Jun 5, 2005, 6:04 PM   #5
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I'm hoping someone has info about this situation...

I went into a local mall camera shop and attached their 2.0x extender to my 1.4x and 70-200mm 2.8 IS. I took a few shots. Mall light is awful, but I still got usable photos at ISO 3200 (I would never use this combo indoors, so I expect it to be much better outside). At first I just tried the 2.0x extender with the lens and the camera indicated an aperture f/5.6. I expected this. What I thought was odd was when I added the 1.4x to the mix, the aperture stayed at f/5.6. I assumed I would lose an extra stop... I figured it must be a rounding issue. I also thought it odd that it was auto-focusing, although it had to hunt a few times.
At home I checked the exif data for each of the photos. They all indicate a lens of 140-400mm. This would be the 70-200mm with 2.0x extender, but it seems to have ignored the 1.4x. Is this normal?
I had everything attached in this order: 20D/1.4x/2.0x/70-200mm.
Should the camera "see" both extenders? If it doesn't see them both, wouldn't it make sense for it to see the 1.4x since it was attached to the camera first?
What am I missing here?

...and another question....would it be possible to use the Sigma 2x extender instead of the Canon2x with the Canon 1.4x?

Any help would be appreciated...

mactek
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Old Jun 6, 2005, 6:05 AM   #6
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Hi

http://www.stevesforums.com/forums/v...mp;forum_id=65

I use the 2x a lot. Quality is good,very goodat f8 and f11. Stacking 1.4 and 2x is not fantastic. But for fun and certain situations have a try with it.
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Old Jun 6, 2005, 8:57 AM   #7
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I still need the answers to the previous questions, but thought I would post a photo I got at the mall. The lighting there is horrible. Shot was taken with the 20D, 1.4x stacked on 2x with the Canon 70-200mm L IS... Exif data shows a focal length of 385mm. It's wrong. It should be 539mm when taking the 1.4x extender into account. It also doesn't take into account the 1.6x crop factor of the 20D.
If my calculations are correct (and they may not be) the focal length would be 862mm. 192.5mm * 2 * 1.4 * 1.6 = ~862mm. I am actually not sure how the extenders mutiply.

Anyway, here's a mall shot f/5.6 1/80s ISO 3200 handheld, no editing other than resizing.
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Old Jun 6, 2005, 8:58 AM   #8
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...and here's the normal, quick sharpen/denoise, etc from Photoshop.

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Old Jun 7, 2005, 6:48 PM   #9
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Ok,

No one seemed to be able to answer the questions here, so I went looking elswhere and came up with some answers. Since 230+ people read this thread, but I only got 3 responses, I figure others might be interested in the answers...

Quote:
At first I just tried the 2.0x extender with the lens and the camera indicated an aperture f/5.6. I expected this. What I thought was odd was when I added the 1.4x to the mix, the aperture stayed at f/5.6. I assumed I would lose an extra stop... I figured it must be a rounding issue. I also thought it odd that it was auto-focusing, although it had to hunt a few times.
Quote:
At home I checked the exif data for each of the photos. They all indicate a lens of 140-400mm. This would be the 70-200mm with 2.0x extender, but it seems to have ignored the 1.4x.
Stacking is apparently something Canon doesn't think anyone should and/or would want to do, so they didn't put all of the contacts on the extenders. The extender attached to the lens will be recognized, but anything behind it will be ignored. This explains the improper aperture reading and will cause the lens to hunt if there isn't enough contrast. It also explains the exif data showing 400mm max focal length. The 1.4x extender was simply not added to the equation. Apparently the numbers change if the extenders are switched.

Most people who are using film think stacking extenders is a bad idea. Most people using digital think it's either ok sometimes or works great depending on what they're shooting. People with IS lenses seem to have no trouble stacking up to 3 extenders and/or tubes.

With this info and the photos I took above, I think I am going to get the Canon 2.0x extender for use with my 70-200mm L IS and 1.4x extender.

Worst case, I can use the 2.0x all by itself....

Hope this helps someone out there...

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