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F2.8 and light with Canon 17-55 and Sigma 18-35

Started Aug 18, 2015 | Discussions thread
jitteringjr Veteran Member • Posts: 3,608
Re: F2.8 and light with Canon 17-55 and Sigma 18-35
1

rweaver85 wrote:

Can anyone who has used both of these lenses tell me which one lets in more light at F2.8?

Sounds like you are asking about measured T stop and that can all be looked up on DXO's website.  I believe the Sigma 18-35 has a actual T stop closer to the f stop the lens displays than the 17-55.   if memory serves me right the 17-55 has a t stop score of 3.4 so it's almost 2/3rd of a stop slower than the 18-35 at f2.8.

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