autofocus speed: aftermarket vs canon

is there a big difference in autofocus speed between canon and aftermarket brands such as sigma/tamron?

This really does depend on the lens
It is safe to say that tamron will not AF as quick as Canon on new lenses - but a Sigma with HSM can sometimes be a match for canon's USM

Ring USM is the King of the Hill IMHO.

delhi wrote in post #2040776
Ring USM is the King of the Hill IMHO.

i agree .
Rob.

Me 2.

I don't ... no difference worth worrying about between HSM and USM most of the time and I have actually owned several of both. USM on my ex 28-135mm IS was poor at best while on my Sigma 100-300mm EX HSM it was amazing. Anyone who tells you there is a blanket difference is peddling an agenda or inexperienced with different brands because the truth is it depends on the lens.

Well I just got my 70-220 2.8 Sigma HSM,and I honestly cant tell any difference from my Canons with USM.I tried a fellow students 70-200 Canon and it really didnt seem much different.

I have to 2nd what Dave said, IMHO thats just the plain truth of the matter. You have to look at each lens on it's own merit, they all differ slightly. Too many variables affect how long it takes a lens to focus. It's not just a matter of USM Vs HSM, it's also a matter of focus algorithms, focal length, speed of light entry and also light scatter/contrasts control.

As someone that absolutely demands the fastest AF possible. I'll toss in my own findings.

1. Many factors contribute to overall focus speed, including overall lens design, prime Vs. zoom, aperture, Body used, and of course focus motor.

2. The fastest AF on an EF mount is the EF USM ring lenses.

3. The fastest these lenses can focus occurs on the 1 series cameras.

4. The fastest combinations are the 1D series with fast primes like 300mm f/2.8L 400mm f/2.8L and 85mm f/1.8 USM. The fastest Zoom I hve ever encountered is the 70-200mm f/2.8L IS on a 1 Series.

5. The second fastest focus motor available for EF mount is definately the Sigma HSM.
No other manufacturer even comes close.

6. I have to disagree with Dave and Mitcon on the comparison of HSM Vs. being inconsequential.
In SOME cases the Sigma not only keeps up but may be faster (100-400mm is notoriously slow USM AF and compared to the faster apertured Sigma 500mm prime or 120-300mm it looses out) .. but Canon's fastest simply beat Sigma's fastest in a noticeable way. Sigma's costliest lens (300-800mm) feels crippled compared to the Canon Big white primes. (Sigma 500mm fairs better but still is slower) to some the difference may not be important but to some it is. Since this is a thread about AF speed, I think it's worth taking into account the subtle differences as well as the astronomic.

Lastly, I want to re-itereate, between Canon USM and Sigma HSM you do have to look at it on a lens per lens basis,
BUT!!!! You do not have to do this with any other lens when compared to Canon USM and Sigma HSM

The Canon USM and Sigma HSM will allways perform better than any other lens for AF speed.

o-kay having re-read the OP..

Canon USM and Sigma HSM are faster than anything tamron has to offer. There is a "big difference" there.

delhi wrote in post #2040776
Ring USM is the King of the Hill IMHO.

amen!

Canon USM AF motors are generally the fastest,Sigma's version called HSM is also about as fast. Tamron and Tokina's AF speeds are a touch slower. AF speeds vary by the model, not just the type of AF motor it has, and the body makes some difference as well.
I have lenses with USM, HSM, Tamron AF, and Tokina AF, and regular AF from Canon as well and actually the biggest diff is the noise level from the motor.

To me, the small diff in AF speed is not that big of a deal.