Incorrect focal lenght using a TC-17E II

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Archive 2009 · Incorrect focal lenght using a TC-17E II

fpimentel
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p.1 #1 · Incorrect focal lenght using a TC-17E II

I have an AF-S NIKKOR 400mm f/2.8D IF-ED lens (Version I) that I have used with the Nikon AF-S TC-20E II (2.x) and the Nikon TC-17E II (1.7x). In theory this lens should be 100% compatible with both of these teleconverters (according to the info posted at the Nikon website) but I am experiencing a weird problem with the TC-17E II and the registered focal length of the lens (when used with this teleconverter). Instead of the expected reading of 680 for focal length I am getting a much higher number of 950 for focal length! On the other hand, the autofocus works OK with the TC-17E II and (as expected) it reduces the lens aperture by 1.5 f/stops (from 2.8 to 4.8).

Generally I use this lens with a D300 but to be sure that the problem was not with the camera I tried the lens with 2 other camera bodies (a D40X and a D700) and I got the same results regarding focal length (950 instead of 680). I cannot understand what is going on since this converter should not increase the focal length of the 400mm f/2.8D IF-ED up to 950. And I don’t have the same problem with the TC-20E II (2.x), since when I attach this converter I get the expected 800 for focal length. To finish, I have tried the same converter with a 70-200 2.8 and it only increases the focal length to the expected (maximum) 340.

I am trying to find a logical explanation to this question (incorrect focal length with the Nikon TC-17E II (1.7x) but I don't have one.

Do anyone have any idea about why this is happening?

Dec 29, 2009 at 04:24 AM

Andre Labonte
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p.1 #2 · Incorrect focal lenght using a TC-17E II

Hmmmm ... never saw this one before. Sounds like some preset in the firmware. I'd check the Nikon tech support web pages.

Dec 29, 2009 at 06:04 AM

davidnholtjr
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p.1 #3 · Incorrect focal lenght using a TC-17E II

fpimentel wrote:
I have an AF-S NIKKOR 400mm f/2.8D IF-ED lens (Version I) that I have used with the Nikon AF-S TC-20E II (2.x) and the Nikon TC-17E II (1.7x). In theory this lens should be 100% compatible with both of these teleconverters (according to the info posted at the Nikon website) but I am experiencing a weird problem with the TC-17E II and the registered focal length of the lens (when used with this teleconverter). Instead of the expected reading of 680 for focal length I am getting a much higher number of 950 for focal length! On the other hand, the autofocus works OK with the TC-17E II and (as expected) it reduces the lens aperture by 1.5 f/stops (from 2.8 to 4.8).

Generally I use this lens with a D300 but to be sure that the problem was not with the camera I tried the lens with 2 other camera bodies (a D40X and a D700) and I got the same results regarding focal length (950 instead of 680). I cannot understand what is going on since this converter should not increase the focal length of the 400mm f/2.8D IF-ED up to 950. And I don’t have the same problem with the TC-20E II (2.x), since when I attach this converter I get the expected 800 for focal length. To finish, I have tried the same converter with a 70-200 2.8 and it only increases the focal length to the expected (maximum) 340.

I am trying to find a logical explanation to this question (incorrect focal length with the Nikon TC-17E II (1.7x) but I don't have one.

Do anyone have any idea about why this is happening?

I had TC read less FL, but never more FL. My 300mm with 1.7 should be 510mm but only reads in the Exif 500mm. My 200-400mm with 1.4 should be 560mm and reads 550mm and 1.7 should be 680mm and only reads 650mm.

I'd say if it AF's fine and has clear pic's then don't worry about it to much.

Dec 29, 2009 at 09:35 PM

Avi B
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p.1 #4 · Incorrect focal lenght using a TC-17E II

Are you perhaps reading the 35mm effective FL somehow?

Dec 29, 2009 at 09:52 PM

skyvan
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p.1 #5 · Incorrect focal lenght using a TC-17E II

Known issue: http://www.fredmiranda.com/forum/topic/830177
No logical explanation either.

Dec 29, 2009 at 10:06 PM

Charles Loy
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p.1 #6 · Incorrect focal lenght using a TC-17E II

The TC17 reads incorrectly with my 300 and 400 2.8 AF-S lenses, but reads correct focal with my older 500mm f4 AF-I lens. Go figure that one out.
But it's a known issue, use the 17 and have fun.

Dec 29, 2009 at 10:09 PM

fpimentel
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p.1 #7 · Incorrect focal lenght using a TC-17E II

Someone suggested that it could be a problem with an intermittent contact between the lens and the teleconverter. I did clean the contacts of the lens with Deoxit but the misreading of the focal length continues. And it is not a question related the so-called the sensor crop factor since it happens both with a full frame body (D700) and a D300. The pictures are OK (not distorted) and everything else seems to be OK (autofocus and aperture) when I use the lens with the TC-17E II (1.7x). I would have to follow Charles' advise and "use the 17 and have fun."

Dec 31, 2009 at 08:36 PM

Go4Long
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p.1 #8 · Incorrect focal lenght using a TC-17E II

davidnholtjr wrote:
I had TC read less FL, but never more FL. My 300mm with 1.7 should be 510mm but only reads in the Exif 500mm.

mine does that too.

Dec 31, 2009 at 09:00 PM


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