Teleconverters

[susie]

Probably a very silly question yet again!!

Why is it that it appears (other than kenko) you can mostly only use teleconverters with that manufacturers lenses, after all if you have a *Canon camera it will take Canon fit lenses from other manufacturer and they will autofocus on it.
If Sigma produce lenses that fit a Canon, the teleconverter fits a Canon body and a Canon fit lens, so why on earth can they not make them so that they can have a Canon lens fitted to them?

*Nikon users please read Nikon where I have typed Canon!!!!!

 

[CT]

Not a silly question at all Suzy.

At it's most basic, a teleconverter is just a magnifying glass which goes between the lens and the camera, so on the face of it, providing the converter lens is accurately ground and polished it shouldn't matter much who actually makes it.

The problem is though, that modern converters at their best also have all the electrical connections to maintain autofocus, image stabiliistion, and probably transfer distance information to the camera/flashgun, as well as transferring updated info to the camera about the new effective aperture and focal length for EXIF purposes.

Not all independent manufactures' converters fulfill all these requirements. If it sounds like I'm a bit of an advocate of putting the manufacturers converters behind their own lenses, then I suppose it's because I am.

Even with Canon lenses, not all are capable of accepting a converter for purely physical/design reasons.

 

[fracster]

I`ve been thinking of selling my 80-400 and getting a Nikon 2x for my 70-200, am I going mad?.....

 

[susie]

I can understand that, its just a shame that if the connectors were for simplicity
1 autofocus
2 IS
3 flash
4 exif

they could not just standardise for example numbers 1-3 so that the lenses would be effective (even if some of the information was missing) and it would not wreck the lens or camera!!

It does not affect me at the moment because I only see me using the Sigma on Sigma tc's because being 2.8 throughout it would only drop to 5.6 on the 2x but it would be so much easier if they were interchangable.

 

[CT]

I`ve been thinking of selling my 80-400 and getting a Nikon 2x for my 70-200, am I going mad?.....

Don't do it!

I have the Canon 70-200 2.8L IS and the Canon 100-400L

The best place for a converter is behind a prime lens if you have to use one. Even the best zooms are compromised compared to a prime lens - adding a converter just compromises them further. That's not to say you shouldn't use a converter with a zoom - just be aware of the issues and don't expect top quality results.

If I use my 70-200 lens with a 1.4TC, I need to stop down a couple of stops before it matches the performance of the 100-400L wide open. Remember I've already lost a stop too because of using the converter.

 

[fracster]

Being housebound for a couple of days and having access to ebay is very dangerous...........:nuts:

Thanks CT.....

 

[Canon Bob]

One other issue that CT didn't mention is that of any interaction between the coatings. I had a Sigma 2x (sold it someone recently...can't remember who to ) and found that it gave a slight colourcast when used with my longer Canon primes....the Kenko and Canon T/C's didn't do this.
I also found it to be true with the 1.4x versions in a controlled test.

Bob

 

[CT]

Good point there by Bob. The multi coatings on modern lenses are hugely important to colour saturation and I know that Canon converters have the same coatings as their lenses - no doubt Nikon and other manufacturers are the same.

 

[susie]

I wonder who you sold it to!! Must admit I did not find anything particularly interesting to shoot with it, but the images were find with the Sigma, and I'm waiting for some decent weather so I can get out and play properly, for some reason the birds don't want to get within range of me - not even a fat ball has enticed them to the garden!!

 

[CT]

Being housebound for a couple of days and having access to ebay is very dangerous...........:nuts:

Thanks CT.....

Believe me -I know that feeling, but don't chuck the baby out with the bath water.