----- Original Message ----- From: "Alex Zabrovsky" <[EMAIL PROTECTED]> To: "EOS list" <[EMAIL PROTECTED]> Cc: "Israel Shapiro" <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]> Sent: Thursday, November 14, 2002 1:27 AM Subject: EOS IS
> 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 > What do I/we think about what? That the 28-135 shouldn't be tripod mounted with the IS switched on? This is true, and apparently for the reasons stated. I have images that bear this out, shot in a room and absolutely steady, there is some blurring. And the long teles do have a sensor for tripod mounting, there is some discussion whether the 100-400 can be, I've heard it both ways. Skip Middleton www.shadowcatcherimagery.com * **** ******* *********************************************************** * For list instructions, including unsubscribe, see: * http://www.a1.nl/phomepag/markerink/eos_list.htm ***********************************************************
