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PostPosted: Sat Jan 12, 2013 12:26 am 
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Joined: Tue Sep 07, 2010 11:13 am
Posts: 131
Hi

I'm looking for a 1,4 teleconverter and I have the Sigma vs Canon dilemma

I found lists of compatible sigma lenses with sigma teleconverters, but nothing on sigma converter on a canon lens.
And nothing on sigma lens with a canon teleconverter.

I tried my Sigma 150 mm with a canon 2.0 teleconverter II and I lost autofocus.
Will it be the same with a canon III?
And will I with a sigma loose autofocus when I use a canon lens?

Apart from 1 f-stop what else will I loose?
Will the image quality be affected a lot?
Is it more with canon or Sigma - I have found no real reviews.

I hope you can help me.

M


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PostPosted: Sat Jan 12, 2013 12:49 am 
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Joined: Sun May 25, 2008 12:48 pm
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Location: UK
Sigma teleconverters have a protrusion so the mechanical compatibility is same as the Canon extender which is similar. There is a model of Tamron which does not have protrusion, I'm not sure what specific model it is though, and Tamron have made plenty of them!

The Sigma 150mm macro does NOT AF with a 2x from Sigma. This is a lens design choice made by Sigma. Presumably the Canon works in the same way with that lens. Both of those report their presence to the lens. A model of Tamron does not report itself to the lens, and therefore may still allow AF in that condition with unknown performance. Again I don't know what model it is.

In general, I would expect the Sigma 1.4x to work where the Canon 1.4x does.

Because you're trading the increased focal length, it does make the focal ratio of the system decrease accordingly. It isn't really a loss, but a shift in what goes where. These work essentially by magnifying the middle of the lens image. Good lenses may have sufficient quality that the resulting quality is still good. Bad lenses wont be helped.

Each model may arguably be better optimised to work with lenses from the same company. I've used the Sigma 1.4x and 2x with various Canon lenses, and in general it does what it is supposed to without significant impact. The only exception is the EF 135mm f/2L lens which really is horrible with a Sigma TC on it. But I think this is mainly due to the '135 being rather fast and also having relatively poor longitudinal CA in the first place.

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Canon DSLRs: 7D, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 50/1.8, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 15-85 IS
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 150 macro, 120-300 f/2.8 OS, Celestron 1325/13
Tinies: Sony HX9V.


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PostPosted: Sat Jan 12, 2013 1:17 am 
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Joined: Tue Sep 07, 2010 11:13 am
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So the extra price of some 50% for canon TC in't really worth it?


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PostPosted: Sat Jan 12, 2013 8:38 am 
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Joined: Sun May 25, 2008 12:48 pm
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I can't really say since I've not used one. As I said, it is possible using the same brand Extender as lens may possibly be better, but I have not tested this.

_________________
Canon DSLRs: 7D, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 50/1.8, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 15-85 IS
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 150 macro, 120-300 f/2.8 OS, Celestron 1325/13
Tinies: Sony HX9V.


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PostPosted: Sat Jan 12, 2013 3:13 pm 
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Joined: Tue Sep 07, 2010 11:13 am
Posts: 131
I just found this list, apparently they are the same when it comes to compatibility, and loss of AF
As for image quality, my thoughts are if you have to make one that fits all brands of camera and lenses, where only the mount differs, then you might have to cut some corners. But I don't know anything about how they are made and if it is even an issue.

[url] http://photography-on-the.net/forum/sho ... =41922/url]


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