[eaglem]

I recently bought a Sigma 70-200mm F2.8 Lens and find it fast in focus and gives good quality photos. I was hoping to add a bit more reach than I'm getting with a Teleconverter, either 1.4 or 2.0 but would like to know what the benefits and drawbacks might be in doing this. Any help would be appreciated.

[Chaos_Realm]

Of the top of my head:

Benefits:
Longer Reach, so if you can't get closer to the subject then this is cheaper than buying a new lens

min focus distance stays the same but focal length is increased. (can be handy for macro but your dedicated sigma's would be best)

Drawbacks:
Slower focus speed
lower IQ
reduces the largest apertures (1 stop for 1.4X and 2 stops for 2X)

their may be some others but that's I all can think of now.

[newarts]

I recently bought a Sigma 70-200mm F2.8 Lens and find it fast in focus and gives good quality photos. I was hoping to add a bit more reach than I'm getting with a Teleconverter, either 1.4 or 2.0 but would like to know what the benefits and drawbacks might be in doing this. Any help would be appreciated.

It is possible that a certain TC can give better sharpness or image quality than simply enlarging the non-TC image. Certainly some TC's are better than others & worth a try if the attendant light loss won't hurt you (even 2 stops (2X TC) should still be ok for your AF).

Actual experience will provide the best guidance; I hope someone will identify a TC that will do what you want. I caution you avoid relying on guesses like "The Kenko XXX works well with my Tamron, therefore it will work well with your Sigma."

If nobody reports positive experience, then I'd make my best guess, buy or rent the TC then critically test it immediately....return it if it fails to improve your images compared to enlarging.

An expensive TC that makes images worse than no TC at all is not a valuable addition to your kit.

[DSims]

Sigma's own TCs reportedly often work well with their lenses, but you'll have to look into the specifics of your combination.

[Lowell Goudge]

What Sigma lens do you have, HSM or not?

The currently available Sigma TCs are not equipped with the KAF2 mount necessary for HSM

Also, I have heard that some of the sigmas, are not as sharp as others at the longest focal lengths.

I believe the origonal APO 70-200F2.8 EX (Non DG NOn Macro) version is the sharpest. the macro version is reportidly s just a little softer at 200mm.

As for the TCs themselves, and with the lens, yes they do work very well.

this was a jpeg right out of the camera just resized

Also note that the sigma TCs feed lens data through the body directly with no intelligence between camera and lens, therefore the camera thinks it has a 200mm not 400mm lens (so SR is not as accurate/effective) and on some bodies the incorrect aperture feedback leads to a constant exposure error that needs to be adjusted out. On my K10D i need .7 stops with a 1.4x and 1/3 stops with a 2x sigma TC on the 70-200

[newarts]

...
As for the {sigma} TCs themselves, and with the lens, yes they do work very well.....

Thank you Lowell that's exactly the kind of precise response needed.

[eaglem]

Thanks for the information, it gives me a bit to consider.

[Lowell Goudge]

which version of the lens dou you own?

It really does make a huge difference in the decision

[eaglem]

It's the Sigma APO DG 70-200mm F2.8 HSM Lens

[selar]

I bought the HSM II version of this lens recently. Have only used it for a few test shots so far, but I feel that the very spirit of this lens is destroyed if you lose the HSM capability. I had only experienced SDM so far, the speed and accuracy of the HSM on this lens is a class apart. The original owner also advised against using Teleconverters with this lens and instead to crop the shots if you needed more detail.

[eaglem]

Thanks, I think forgetting about a teleconverter for this lens would be a wise move.

[selar]

Yeah, I tried one of the two TCs capable of transmitting HSM - Kenko Pz-Af 1.5x with my lens, it hunts a fair bit at the long end. You can possibly work around by shortening the focal length to about 150, locking focus and then zooming back out, but thats not really going to work for your bird shots. Might work for your bird bath shots though. Theres another problem with the Kenko, it just seems to pass through the lens aperture information without modifying it as also the focal length information.

[Lowell Goudge]

Thanks, I think forgetting about a teleconverter for this lens would be a wise move.

Unless sigma comes out with an hsm version of the existing TCs. Then it might be worth it, as it was for mu version 1 APO 70-200

[kheldour]

I had the combination 70-200 2.8 with a 2x converter on my older Canon. It worked flawless, focal length is doubled, you loose 2 stops, but IQ is still very good.

No problems with the HSM/USM-drive.