Buying a USED 17-40 F/4L on Friday, got some questions...

This is my first post here, great forum you guys!

• What is the best way to test if I got a sharp copy?
  
• At what mm / aperture is it the sharpest?
  
• Do I need the lenshood on my 1.6x XT Rebel?
  
• Recommend me a nice circular polarizer (77mm)

TIA

Felix

You'll get different answers for these questions, here's mine.

• What is the best way to test if I got a sharp copy? Use it in real life situations. If you like the pics it's a good one. I have never taken a picture of a chart or ruler and I like my lenses just fine.
  
  
• At what mm / aperture is it the sharpest? Anything over f/4 is amazing on my copy, but f/4 isn't that bad either. You'll get different performance at either side of the zoom. I am happy with both ends of mine.
  
  
• Do I need the lenshood on my 1.6x XT Rebel? I always use a lens hood. 100% of the time.
  
  
• Recommend me a nice circular polarizer (77mm B+W makes nice filters.
  

FelixW wrote:
This is my first post here, great forum you guys!

• What is the best way to test if I got a sharp copy?
  
• At what mm / aperture is it the sharpest?
  
• Do I need the lenshood on my 1.6x XT Rebel?
  
• Recommend me a nice circular polarizer (77mm)

TIA

Felix

Welcome to the forum

The 17-40 is a very nice lens and a wise choice. I would test it by shooting test shots at all apertures and check the corisponding images carefully for exposure and focus abnormalities. If they are all sharp, show good contrast and exposure you should be fine. Listen and feel for the zoom and focus rings, if they sound like theres grit or they don't rotate smoothly then there could be trouble ahead.

A lens hood is a must IMO. It reduces flare, increases contrast but above all is a good way to protect the end element on the much more expensive lens.

Welcome aboard ... my copy is amazingly sharp at f/4 so hopefully yours will be too.

Yes to the Lens hood ... if you can afford the extra cost get the: EW-83DII Lens Hood

As for filters I use Pro Series Hoya's but this Lens doesn't require a wide angle slim type at all. Just make sure you get a good Multicoated one and they can generally be found for less than $80.