----- Original Message ----- 
From: "Peter Hancock" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Tuesday, March 21, 2006 12:16 PM
Subject: EOS to filter or not...


As a postscript to the recent thread on whether to put filters on by
default, I just tested my 100-400L with and without the rather ordinary
Jessops filter that I got with it.  Not much at 100, but at 400 there is
a visible reduction in resolution and contrast.  I'll try again after
I've given it a really good clean :-)

Peter
________________________________________
Peter,

Long focus lenses are quite critical about the quality of glass used as a
filter.
Some years ago I was unable to focus on infinty with my 300 f4.5 - simply
because the so-called filter was acting as a weak close-up lens with a focal
length of round 20m.  Removing it, or changing to a decent Hoya allowed
focus to infinity, and I didn't notice any degradation in quality (with the
Hoya fitted).


Malcolm
Milton Keynes, UK
http://www.megalith.freeserve.co.uk/oddimage.htm




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