Questions about teleconvertors

[Deleted member 11679]

Howdy do,

In my ever on-going weighing up of a zoom lens for the Motorsport season this year, I now have a few quite simple questions (probably) about teleconvertors.

Will a Canon 1.4x or 2.0x convertor work with Sigma lenses? Or are they specific to their range of gear? And is the same in the opposite direction to, will Sigma convertors work with Canon gear? If so, which are the best to get?

I understand that when you apply a 1.4x convertor you lose one stop on the f/ number, and then 2 stops on the f/ number for a 2.0x convertor. However, is the 2 stops across the zoom range on the 2.0x convertor or is it only after a certain amount of zoom is applied?

My reasons for asking this was that I first weighed up the Canon 70-200 f/4 L lens, then the Sigma 100-300 f/4, and now I am currently thinking the Sigma 70-200 f/2.8 as this would allow me to use it in darker locations i.e inside gyms or swimming pools!

I'm quite pleased I have got a couple of months to weigh these ideas up as I really want to get the right lens for me (sports shooting Motorsport, swimming and other events.)

 

[spell]

The convertors SHOULD be compatible across both brands.

And you loose the stops across the range.

 

[Golden Ape]

Actually I think - pretty sure - that the canon teleconverters are only meant to work with Canon L class lenses. I think the sigma ones are good to work with any lens though. Worth checking Canon's site though.

 

[Johnny|lucidcomposure]

Actually I think - pretty sure - that the canon teleconverters are only meant to work with Canon L class lenses. I think the sigma ones are good to work with any lens though. Worth checking Canon's site though.

There is a compatability chart regarding what they are compatable with.

If you got the Sigma F2.8 and used the converter, You will maintain some more DOF through the wider range where as if your maximum was F4. You would be looking at smaller F numbers which would be a pain when it comes to dim lighting.

I think the best thing to do would be to choose what lens you want. Then rent a teleconverter for a day (£12 ish) to see what sort of affect it will have for you. The Canon's are about £280 and to me thats a lot of money to spend on something not to be sure about.

 

[rpstewart]

^Yup, Canon teleconverters will only work with certain L lenses. This is due to them having a protruding front element which fits into the space between the lens mount and rear element of the main lens.

Sigma TCs should work with all brands of lens but there is a quality issue to get past, even the Canon TC noticeably degrades the image.

And the problem - you may lose AF depending on the lens/TC combination. On prosumer bodies you'll lose AF if the maximum aperture of the combo is smaller than f/5.6 or f/8 on a 1 series.

 

[Matt]

Here's a table for the Sigma TCs showing whether you get AF or not
http://www.sigma-photo.com/lenses/lenses_tele.asp
or
http://www.sigma-imaging-uk.com/support/tele-converters_comp.htm

Most of the time the 2x TC will mean you get no AF

 

[TRiP]

i have the sigma 70-200 2.8 and i just picked up a 2x tc. the first thing i noticed was a drop in af speed and hunting in low light/contrast. gues the latter is due to less light getting through.

havent had a chance for a proper test yet but ill post the results up when i get them.

 

[Deleted member 11679]

Interesting reads so far, thanks. After seeing quite a lot of photo's now with the 70-200 f/2.8 I am really impressed so far, my other thought with this is, that if I buy a Sigma 1.4x TC then I will effectively have a Sigma 100-300 f/4 on my hands!

 

[TRiP]

tested the lens and tc today and i was pleasantly suprised.

shooting wide open with the tc attached (f5.6) gives about the same sharpness and contrast as shooting wide open with no tc attached(f2.8).
the only concern now is af speed and hunting which shouldnt be to much of a problem in bright conditions.

 

[Deleted member 11679]

tested the lens and tc today and i was pleasantly suprised.

shooting wide open with the tc attached (f5.6) gives about the same sharpness and contrast as shooting wide open with no tc attached(f2.8).
the only concern now is af speed and hunting which shouldnt be to much of a problem in bright conditions.

Any chance of some test shots TRiP? So have you got the Sigma 2x convertor or the Canon one?

I was looking on Pbase at a lot of photo's produced by this lens, there was some great F1 shots even with what appeared to be a 2x convertor and at 400mm.

 

[Joe T]

Im going to pick up my Sigma 1.4tc today - yay!

 

[TRiP]

Any chance of some test shots TRiP? So have you got the Sigma 2x convertor or the Canon one?

i got the sigma one. the canon one isnt much more expensive though im not sure about compatibility.

anyway, test shots. they arent the best but give some sort of idea about sharpness. these are all 100% size crops of the centre of the image. wouldn't normally test a lens this way but i havent had any free dayight time to use the lens this week.

200mm(no tc) at f2.8


200mm at f5.6


400mm(200mm + 2x tc) at f5.6

 

[Deleted member 11679]

Interesting, still hard to judge but I will watch out for photo's, thanks.

Joe, let me know how you get on with your 1.4x mate.