Due to the possible fault of the IS in my 28-135 I searched the net for any related info and this is what I have been stumbled upon:
Date sent: Sat, 10 Jul 1999 23:04:48 -0700 (PDT) From: Patrick Chase To: [EMAIL PROTECTED] Subject: Re: EOS: IS lenses on tripod? Send reply to: [EMAIL PROTECTED] " EOS wrote: > Why does my 28-135 IS manual state that the lens should not be tripod mounted > for any reason? Can anyone tell me why doing so (putting aside that it's > simply unnecessary) is not good? You're misreading the manual; What it says is that the lens should not be tripod-mounted _with IS switched on_. The reason, according to a Canon rep, is that the IS system can get into an oscillation which may cause it to burn itself out if it is left on with the lens mounted to a tripod. I don't know if I believe that or not. I'm a bit rusty on digital motion controls, but I do know that such a thing is very much possible. In any case, the new IS super-teles auto-detect when they're on a tripod, and switch to a different set of IS control laws (presumably ones geared towards dealing with the smaller amplitude, higher-frequency vibrations typical of tripods. My guess is that to do this Canon had to increase the IS measurement frequency beyond the 7 Hz used in the present lenses, since tripod- mounted vibrations typically have frequencies of several Hz or more; If they kept the sampling frequency at 7 Hz the servo would tend to go unstable due to inadequate sampling rate alone, regardless of the control laws...) -- Patrick " What do yuo think abot that ? Regards, Alex Z * **** ******* *********************************************************** * For list instructions, including unsubscribe, see: * http://www.a1.nl/phomepag/markerink/eos_list.htm ***********************************************************
