Benjiphoto
newbie
Reged: 23/08/2006
Posts: 16
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Hi
I'm in the market for a 70-200 and I'm considering the 'Sigma 70-200mm f2.8 APO EX DG Macro HSM II Lens' or the new 'Tamron 70-200 mm F2.8 Di LD (IF) MACRO'. Has anyone had any experience with both of these? The Tamron has been out for a couple of months now but there doesn't seem to be any reviews online or in magazines.
Also, will both work with either a Sony or Sigma 1.4x/2.0x Teleconverter?
Thanks
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Roger_Provins
Made-it Man
Reged: 22/10/2005
Posts: 2836
Loc: Gloucester, UK
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Neither seem to be yet available in UK (at least) in Sony (or Pentax) mount. Although they're both listed on the Dyxum web site neither has a user review yet which generally means no one anywhere has got their hands on one yet.
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Rog
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El Sid
Going potty
Reged: 14/04/2003
Posts: 9311
Loc: Sussex-by-the-Sea
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As yet the new lens is not listed in Sigma's teleconverter list in Sony fit. It is listed under Sigma, Nikon and Canon fit as being fully compatible so I'd be most surprised if the Sony version isn't as well... Also the lens's page doesn't suggest that any issues are to be expected with Sigma's own converters.
Chances are the Tamron would probably be OK as well though it would pay to carefully check that there is no chance of the Tamrons exit lens coming into contact with the front lens of the converter.
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Nigel
Completely BSRIPN 
ElSid Gallery
A camera in the hand is better than one in the cupboard........
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Benjiphoto
newbie
Reged: 23/08/2006
Posts: 16
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That compatability chart is really useful. Do you know if there's a similiar one for Sony's own teleconverters. They say the 1.4x is:
"Designed to support Sony G-Series 70-200mm f/2.8 G Telephoto Zoom and Sony G Series 300mm f/2.8 G Telephoto lenses, as well as the unique Sony 135mm f/2.8 STF (Smooth Transition Focus) lens".
It's unclear whether third party lenses would work or not. I presume they would if they fit the camera but then you know what they say about presumption...
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El Sid
Going potty
Reged: 14/04/2003
Posts: 9311
Loc: Sussex-by-the-Sea
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Difficult to say. Probably the Sony converter would work with a 3rd party lens but there may be an issue of communication. Dedicated OEM converters, I believe, report the effective aperture and focal length (ie the set value multiplied by the conversion factor) back to the camera (for EXIF data etc). Obviously this is fine with the OEM lens but if the data from a Sigma (for example) is not an acceptable format for the Sony converter to work with problems may ensue - a bit like the communications issue between older Sigma lenses and later Canon digitals.
Again you'd have to be very sure of clearance between the lens' rear element and the converter's front one...
Cheaper converters like the Teleplus simply pass the lens data straight through to the camera so there's no question of data failure and the suchlike - though this means you may have to guess which images you used the converter with. Cheaper converters also tend to have recessed elements which makes them compatible not only with the fancy expensive lenses but also with all the mid-range and budget models too.
Also because they don't recalculate the lens data the camera won't disable the AF system if the effective aperture is too small - <f5.6 or 8(depending on model) - meaning that the camera will try to autofocus even if the effective aperture is way too small. I have a Teleplus MC7 2x and have used it successfully in AF with an F4 zoom - a proper Canon converter would have disabled the AF...
In the end you pay your money and make your choice: matched converters such as the Sigma and Sony ones offer the best retention of image quality and pass accurate info back to the camera, but on a restricted range of lenses, while the cheaper ones will degrade the image more but are AF and mechanically compatible with just about every lens - though you will have to guess the effective aperture etc...
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Nigel
Completely BSRIPN
ElSid Gallery
A camera in the hand is better than one in the cupboard........
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