----- Original Message ----- From: Petja Aaltoluoto <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Thursday, January 03, 2002 9:39 AM Subject: EOS 3rd party TCs causing vignetting
> Hi all! > > A friend of mine (though he's shooting with Nikons) and I both have an > older AF version of a Sigma 1.4X TC, and I use it on my Canons and he on > Nikons. > > We started to discuss the quality, and noticed that vignetting may be > somewhat heavier on pictures taken with my EOS than those taken with > Nikon. And the model of the TC is exactly the same, and the lenses are > comparable by focal length, max aperture and optical quality. > > Then, my friend spotted (he just emailed me) that on a test in a Swedish > (no, for God's sake, I'm not Swedish! ;) ) photog mag FOTO they marked that > most 3rd party TCs perform more poorly (talking about vignetting, not the > sharpness or anything else) with EOS lenses that with Nikkor lenses. > > Can this be true? > > My friend thought/asked that can it be due to the large diameter of thje EF > bayonnet compared to eg Nikon's own? Maybe Canon uses larger diameter with > lenses, too, and therefore 3rd party TCs that have smaller lens diameter, > caud more vignetting with EF than Nikkor (or Minolta or...) lenses. > > If someone is an expert on this (I'm not) please tell us how it is. > > Regards from FINLAND, > Petja I have both the original Canon 1.4x and a Tamron 1.4x. The diameter of the glass elements is much less in the Tamron and I have noticed vignetting occasionally - but its design allows me to use it with most of my Canon EF lenses if I really need it. The EF throat diameter is large (viz: can accept an EF 50 f1.0L) and 3rd. party converters are probably designed for the practical smallest diameter system they have to fit, with changes only being made to the metal lens mount. As Nikon lovers will always tell us, the Nikon lens mount hasn't changed since about 1960 whereas Minolta and EOS are quite recent introductions. --- M Stewart Milton Keynes, UK * **** ******* *********************************************************** * For list instructions, including unsubscribe, see: * http://www.a1.nl/phomepag/markerink/eos_list.htm ***********************************************************
