[火Ken]

本人想增鏡，小弟用緊40D，已有支A16，小小白，Sigma 30mm f/1.4，及一支Canon 10-22mm f/3.5-4.5，風景多數用10-22mm，但我支A16係多數係室內用埋閃光燈映多，但有時暗處對焦方面比較困難咁........吹脹！所以先想添置鏡頭取代佢，心目中想換Canon 16-35mm f/2.8L，但價錢實在救命，加上我朋友不推介，所以打消左，現在有支 Canon 17-40mm f/4.0L USM 及 Canon EF-S 17-55mm f2.8 IS USM 做選擇，職業攝影就支持前者，因後者不值，但我又好似賣左支 A16，再買支同range唔知算？所以幾苦惱！各位有經驗既 C hing 前 輩 請指點迷津！thank you！

[tcfreeman]

if you shot a dim light conditions, trun to manual focus, that is faster,
for me, personally, at the moment, no need add any lens, because, you already have some good lens coverage from 16-320mm range (ff 135 mm)

[Mcdullchan]

Try to consider the 24-105mm f4L IS USM len