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Old 19-11-12
David Morison David Morison is offline
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Teleconverter conundrum

I've done a fair bit of researching into getting a 1.4x Teleconverter for use with my Canon 7D and 400mm f5.6L. The predominent factor is that as a TC would push the effective maximum aperture beyond the f5.6 thresh hold and that the camera therefore will not AF properly. One solution quoted is to tape of the 3 left hand pins out of the 11 on the TC which sounds OK but when I examine my 7D I find it only has 8 pins and the 3 left hand ones on the lens or TC won't connect to anything! So why does taping off make any difference? I know all about the reporting/non-reporting to Exif but at the moment it's the AF that I am interesting in. Can someone with a lot more technical know how than me shed some light on this conundrum?

Many Thanks

David
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Old 19-11-12
John Perriment John Perriment is offline
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Re: Teleconverter conundrum

You wouldn't have this problem with the ZD 300mm f2.8.
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Old 19-11-12
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Re: Teleconverter conundrum

Quote:
Originally Posted by David Morison View Post
I've done a fair bit of researching into getting a 1.4x Teleconverter for use with my Canon 7D and 400mm f5.6L. The predominent factor is that as a TC would push the effective maximum aperture beyond the f5.6 thresh hold and that the camera therefore will not AF properly. One solution quoted is to tape of the 3 left hand pins out of the 11 on the TC which sounds OK but when I examine my 7D I find it only has 8 pins and the 3 left hand ones on the lens or TC won't connect to anything! So why does taping off make any difference? I know all about the reporting/non-reporting to Exif but at the moment it's the AF that I am interesting in. Can someone with a lot more technical know how than me shed some light on this conundrum?

Many Thanks

David
I tried this some time ago and couldn't get it to work properly, although I have heard of those that have made it work. Ficus though is very slow and if light levels drop its all but unusable. The 7d is a high quality camera my sujestion would be to settle for cropping the image. My own technic was to shoot in RAW on in the RAW converter crop as desired and up the resolution to what it would have been before the crop, in other words interpolate.
Interpolation had a bad reputation but that was in the days of low resolution cameras, modern high resolution cameras have much more information to work with and excellent results can be had. On One do software specifically for upsizing images give their free trial a go and see what you think.

Patrick
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Old 19-11-12
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Re: Teleconverter conundrum

Maybe that method only works on full frame EOS bodies?

Have you actually trued auto focusing with a converted fitted? Does the camera prevent AF with that maxiumum aperture or is it simply less dependable?

Ian
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Old 19-11-12
David Morison David Morison is offline
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Re: Teleconverter conundrum

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Originally Posted by John Perriment View Post
You wouldn't have this problem with the ZD 300mm f2.8.
True but I would have missed half the shots I've got since swapping and would have very tired arms!

David
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Old 19-11-12
David Morison David Morison is offline
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Re: Teleconverter conundrum

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Originally Posted by Ian View Post
Maybe that method only works on full frame EOS bodies?

Have you actually trued auto focusing with a converted fitted? Does the camera prevent AF with that maxiumum aperture or is it simply less dependable?

Ian
No, I haven't bought one yet but researching loads of websites indicates that the problem exists more with the Canon EF 1.4x and that the Kenko works on more Canon lenses than the Canon does! All reports rate the Kenko as highly as the Canon apart from a little softening at the edges at full aperture, which I wouldn't use anyway - even on the Olympus ED300mm f2.8 with TC14 it was necessary to stop down to f6.3-7.1 to get the best results.

Useful link here, will need translating:

http://www.traumflieger.de/desktop/t...est2_teil4.php

Extract from this website:

"The overall win goes to the Kenko 1.4x Pro 300 , which just before the Kenko 1.5x MC DG due to the smaller open-aperture vignetting and better exif correction has the edge. Canon Extender EF 1.4x II shows resolution weaknesses in the border area on Full format and prone to chromatic aberrations. The lack of compatibility due to the protruding front element and a not quite optimal performance in our autofocus test range for the 4th Space - it may also handle the exif data correctly and be of the production quality as well as the purchase price located at the top."

David

Last edited by David Morison; 19-11-12 at 02:12 PM.
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Old 19-11-12
John Perriment John Perriment is offline
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Re: Teleconverter conundrum

Quote:
Originally Posted by David Morison View Post
True but I would have missed half the shots I've got since swapping and would have very tired arms!

David
I know David, I said it tongue-in-cheek!
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Old 19-11-12
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Re: Teleconverter conundrum

Quote:
Originally Posted by David Morison View Post
No, I haven't bought one yet but researching loads of websites indicates that the problem exists more with the Canon EF 1.4x and that the Kenko works on more Canon lenses than the Canon does! All reports rate the Kenko as highly as the Canon apart from a little softening at the edges at full aperture, which I wouldn't use anyway - even on the Olympus ED300mm f2.8 with TC14 it was necessary to stop down to f6.3-7.1 to get the best results.

Useful link here, will need translating:

http://www.traumflieger.de/desktop/t...est2_teil4.php

Extract from this website:

"The overall win goes to the Kenko 1.4x Pro 300 , which just before the Kenko 1.5x MC DG due to the smaller open-aperture vignetting and better exif correction has the edge. Canon Extender EF 1.4x II shows resolution weaknesses in the border area on Full format and prone to chromatic aberrations. The lack of compatibility due to the protruding front element and a not quite optimal performance in our autofocus test range for the 4th Space - it may also handle the exif data correctly and be of the production quality as well as the purchase price located at the top."

David

The question is not which converter you go for but if. Incidentally there is now a Canon extender III which is reputed to address shortcoming in version II at a cost.
Your f5.6 becomes f8 with the converter fitted. The only Canon camera I am aware of that will AF at f8 is the 1D range, hence you question about taping up the contacts. If you do further research about this you will also come access warning of pushing a camera into areas it is not designed for, stress on the focus mechanism appears to be top of he list. Rather bad AF performance particularly in poor light, hunting being the problem.

I maintain upsizing your file and cropping to be a better option, or go the extra expense and buy a 500mm lens, or a wider aperture lens that will accept the converter properly.

In the end it is all a compromise over the full optic quality of a 500mm. A 1x4 converter can give excellent results almost indistinguishable, but there is a slight loss in quality be it very much within acceptable limits depending on the quality of the converter.
A friend at the club also a 7D owner maintains upsizing a file to be equally as good as a converter.

Patrick
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Old 19-11-12
Mike Parr Mike Parr is offline
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Re: Teleconverter conundrum

Hi David I have one of the Kenko 2X converters for my Nikon I havent really used it yet as I havent had the situation, I was tempted to try it in anger on Sunday at the beach but was not keen on switching lenses with all the fine spray about.
That said a couple of test shots with manual focus were ok for quality and I did manage to get AF to work during a bright spell of sunshine.
I am off work on Wednesday and its supposed to be sunny so I'm going to try and get to grips with it and I'll post any results if you like.

Mike
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Old 19-11-12
David Morison David Morison is offline
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Re: Teleconverter conundrum

Thanks for all the replies, I will try interpolating a cropped image to see how I get on - never done it before. However it is not something I am too concerned about as I would only use it on a tripod or other support on fairly static subjects so MF would be the method of choice. I was just inquisitive about the eleven/eight pins mystery - still don't understand that!

Thanks

Regards

David
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Old 19-11-12
Mike Parr Mike Parr is offline
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Re: Teleconverter conundrum

I'm confused too now, Both Nikon bodies have 8 contacts, My kit lenses have 7 each, the Kenco Converter has 8 as does my Nikon35mm
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Old 19-11-12
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Re: Teleconverter conundrum

Quote:
Originally Posted by Mike Parr View Post
I'm confused too now, Both Nikon bodies have 8 contacts, My kit lenses have 7 each, the Kenco Converter has 8 as does my Nikon35mm
2x converters of any quality do loose definition, how much will depend on how good the original optic. A converter is in simple terms a sophisticated magnifying class, so it magnify's deficiancies the original optic has, a 2x probably finds more than a 1x4. Not to mention the loss of two stops.
I have used a 2x and was not impressed.

Patrick
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Old 20-11-12
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Re: Teleconverter conundrum

Interesting discussion here - I will have to try the various theories out!

I have 150mm Zuiko Digital f/2 and so using an EC-20 2x converter it becomes a 300mm f/4. I also have a Zuiko Digital 300mm f/2.8 so it will be fascinating to compare these.

Now that cameras have very high resolution sensors it may be that the need for converters is much less. But of course they weren't always like that - I posted some 3 megapixel Canon EOS-D30 shots from 11 years ago just yesterday

Here is an image that represents just 3 of the 16 megapixels of the original frame:



And it was processed from a JPEG because at the time there was no Lightroom support for this camera (Olympus OM-D E-M5). It was also shot at maximum aperture, using a long zoom (600mm equivalent at the tele end).

Ian
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Old 20-11-12
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Re: Teleconverter conundrum

Hi David

From my own experience. I can assure you that the Kenko Pro 300 will give you auto focus with a lens of f5.6.

I have a relative who uses this combination all the time, and it works fine !

Also, I advised a member in another photo forum of the same. She now has the Kenko Pro 300 on her 55 - 250 f5.6 and is thrilled at the auto focus.

Try it. You wont be sorry !
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Old 20-11-12
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Re: Teleconverter conundrum

Quote:
Originally Posted by Garry View Post
Hi David

From my own experience. I can assure you that the Kenko Pro 300 will give you auto focus with a lens of f5.6.

I have a relative who uses this combination all the time, and it works fine !

Also, I advised a member in another photo forum of the same. She now has the Kenko Pro 300 on her 55 - 250 f5.6 and is thrilled at the auto focus.

Try it. You wont be sorry !
I think it important we know the camera your relative is using, all cameras are not the same, auto focus sensitivity can vary between models and brands. Converters change the effective aperture, a f5.6 lens becomes a f8 lens with the 1x4 converter attached, very few cameras auto focus easily at this aperture. If David can try it before buying and it works satisfactorily that's fine.
We don't want David spending his hard earned cash rashly.

Patrick
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