Difference between DC and USM AF?

Discussion in 'Photography Beginners' Forum' started by inTempus, Dec 27, 2008.

  1. inTempus

    inTempus TPF Noob!

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    I'm looking at buying a Canon EF 75-300 and the price on Buy.com seems pretty good. In the description it says that it uses a DC drive for the auto-focus vs. a USM. What does that mean and is that bad?

    Thanks!
     
  2. rufus5150

    rufus5150 TPF Noob!

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    In the Canon world, USM are quiet and fast. Non-USM are not (in my experience).
     
  3. Jaszek

    Jaszek No longer a newbie, moving up!

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    USM stands for Ultra Sonic Motor, which means that it's silet b/c there are magnets in the lens instead of a motor to focus. And I have no idea what DC is lol. I gues it means not USM.

    YAY 100th post :p
     
  4. gsgary

    gsgary Been spending a lot of time on here!

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    Have you looked at the Sigma 100-300F4 much better lenses
     
  5. inTempus

    inTempus TPF Noob!

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    Thanks everyone.

    I haven't looked at Sigma lenses. I was reading on one of the review sites that their lenses are hit or miss on how high quality their optics are. One reviewer said he got the same lens 3 times (original purchase + 2 replacements) and the each had their own problems.

    Was that just a fluk?
     
  6. Josh66

    Josh66 Been spending a lot of time on here!

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    I don't think flukes happen three times in a row...

    I would stick with Canon glass, but if you want to go 3rd party - that's fine too; lots of people seem to like them. (Then again, you hear stories like the one you heard...)

    I have the lens you're looking at (the Canon 75-300). It's OK, especially for the price. With lots of light you can still get pretty good results from it. Just don't be expecting "L" quality.
     
    Last edited: Dec 27, 2008
  7. Josh66

    Josh66 Been spending a lot of time on here!

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    Back to the main question though - the difference. The most important difference for me is that non-USM lenses don't have full time manual focus (you have to switch it over to manual, on a USM lens you can manual focus even when the lens is on AF).

    USM is a lot faster too, but that's been said already...
     
  8. tsaraleksi

    tsaraleksi TPF Noob!

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    USM also tends to be more accurate.
     
  9. gsgary

    gsgary Been spending a lot of time on here!

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    The 100-300 is a top lens FM Reviews - APO 100-300mm f4 EX IF HSM
     

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