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Added on March 17, 2009, 3:58 pmhow about this one bro viking

chiggy, if you are fine with the focus of the 75-300mm New, the Tamron 70-200mm F2.8 should be faster to 'discover' focus (but not necessarily drive there fast) as it has a bigger eye namely the F2.8 aperture. The Sigma is terribly soft at close range at 200mm F2.8 but it is better at further ranges... how much better I don't know but the Sigma is great at 70mm F2.8 even at close focus.

Do you hear AF sounds on other people's lenses, silent or not, when shooting an event? I don't.

The AF/MF clutch of the Tamron is clunky though.

millenia3000, some IR filters are made as solid glass, some as gelatin sheets (gels). They are not the same as flash gels though, which help to change the color and temperature of light.

achew:

'classic' portrait lengths:
1) 58mm on APS-C (also equal to) 85mm on FF
2) 85mm on APS-C (close to #3)
3) 90mm on APS-C (also equal to) 135mm on FF

Yes you can use your Tamron 90mm F2.8 Macro as a 'classic' portrait length lens.

Then again a lot of great portraits use wider lenses and include the background and setting. For example, a portrait of a bookstore owner... how does your portrait tell people what he/she does?

Or this guy; if you took just a headshot of him, what does he do? He could work at a construction site if you didn't see the whole picture.

http://www.flickr.com/photos/davidhobby/3298614908/

Portraits don't have to have a creamy background.