SIGMA 18-200mm II DC OS HSM vs Tamron 18-270mm PZD

Started Mar 4, 2012 | Discussions thread
MBLB
MBLB New Member • Posts: 14
Re: SIGMA 18-200mm II DC OS HSM vs Tamron 18-270mm PZD

I believe that what m7svk is saying that when the Tamron is zoomed to 270mm it is actually only zoomed to 220mm.
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Yes, that's how I read it too, but it doesn't make sense. I've never heard or read about lenses that aren't the vocal distance that they are sold for. In none of the reviews about this lens it says it isn't 270mm but 220mm. In fact...with the crop factor it's even more. Unless I'm missing something here? And why would the Sigma 18-200 be 200mm for real? How was this measured?

Not sure exactly how the measurement is done but I've read reviews where it's been stated that the actual maximum focal length is lower than advertised. Here's an example of four lenses where none of them are rported to achieve the maximum advertised focal length:

http://www.juzaphoto.com/article.php?l=en&article=35

Thanks for the link Pete. I see the Tamron 18-270mm in this test isn't the PZD version, so not sure if that one has less real focal lenght too. I wonder if the difference in real focal lengt doesn't count for all lenses then (except for primes).
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Regards,
MBLB

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