Expert: Abe - 12/16/2007

Question
QUESTION: Is the difference enough between USM and DC AF (motors?) to spend the extra money for the USM.  The cheapest new USM I can find is $199.  I can find DC lenses for around $120.  What do you think?

ANSWER: Hello, and thanks for your question!

This is a very important question because the differences in these two lenses are very real. As you mentioned, one lens has a DC Motor. Lenses with DC Motors tend to focus both slowly and make more noise. The USM (ultra sonic) Motor focuses more quickly and with less noise. However the USM Motor in the 2nd of these lenses is a "MICRO" USM, and not a "RING" USM motor. The MICRO USM Motor represents a cheaper, lower quality USM than RING-type USM. Nevertheless, any USM is better than a DC Motor. Is the difference between the MICRO USM and the DC Motor worth the slightly higher price of $79 more? Yes, I think it is.

Be careful where you purchase from, though. Use resellerratings dot com and evaluate the stores you plan to purchase from, if you are purchasing online. There are many "bait and switch" companies on the internet, with unbelievable low prices, that will intentionally hold back normally supplied accessories and warranties to lower their costs.  

If I can be of further assistance, don't hesitate to ask again.

All the best!
Abe

---------- FOLLOW-UP ----------

QUESTION: Thank You!  Great answer. I have one more question.  What brand lenses have the "ring USM" rather than the "micro".  I have been looking at all Canon lenses.  How do you feel about the after market brands, since they are less expensive?  ie...Tamron or Sigma.  I also cannot find out what motors they have...


Answer
You're welcome!

Canon uses USM, other brands have their own designations for fast-focusing and silent autofocus lenses. But only Canon calls their fast-focusing lenses "USM." Sigma uses "HSM" (Hyper Sonic Motor) on their higher-end products, and you will find variations with similar names across most of the major lens manufacturers. Typically, the HSM, or whatever names other manufacturers use, are close to, but not as fast or silent as Canon's Ring-USM.

Tamron and Sigma make many great lenses, but typically, they are not up to the same standard (optically) as Canon or Nikon. They may have a durable build quality (depending on model) but typically, they are not as sharp. Sometimes, even their high-end lenses (HSM, etc.) don't do so well, in terms of autofocus - in comparison to Canon lenses of the same focal length. There are exceptions however.

If I were in the market for a Canon that zooms out to 300mm, I would opt for the Canon 70-300mm f/4-5.6 IS USM. While this only has a "micro" and not a "ring" USM, the lens itself is image-stabilized, which means it has the ability to shoot at lower shutter speeds without causing blurry images. I haven't personally used this lens, but I can tell you with a fair amount of certainty that it is built better than it's non-image stabilized counterparts, meaning it will be more durable and take more of a beating. It is significantly more expensive at around $550, but I'm not sure I would find a 300mm zoom lenses useful without image stabilization unless I always planned on using a tripod.

Sigma and Tamron don't do real well in this class of lens unless you go for their high-end, professional lines. But you'll be paying a lot of money on an aftermarket lens, which may have focus problems, as my Tamron 24-135mm lens did, so I don't see any good reason buy the Sigma/Tamron in this class of lens.  If I wanted a short zoom (say, a 17-70mm) or a long prime (say, a 400mm) - I might consider the cost savings and go with a Tamron/Sigma. But in the 70-300 zoom category, I like the many choices Canon has to offer the best.

Good luck, and come back any time with your questions.

All the best!
Abe