I have read that the manual focus is a 'focus by wire' system which supposedly means that when one turns the focus ring on the lens, a 'signal' is sent to the focus motor which then moves the internal optics.
So are you saying that the motor does NOT need to be powered up for the internal focus mechanism to function properly in manual focus mode?
Ian.Dobinson wrote:
if its anything like my 28-80L which i think has the same focus by wire system the NO IT CANT .
it has to be mounted and the CAMERA TURNED ON . if the camera is off or goes to sleep then you cant manual focus .
Well that's a bummer. Kind of what I suspected.
I imagine the FD all manual version is nearly impossible to find in excellent condition.
I guess there's always the Contax/Zeiss 200mm f2 aposonnar. It's a bit slower, and apparently not quite as sharp wide open, but available (used) and fully manual.
\begin{quotation} "The following lenses are old-style electronic full-time manual USM lenses:
EF 50mm 1.0 L USM
EF 85mm 1.2 L USM
EF 85mm 1.2 L USM II
EF 28-80mm 2.8-4 L USM
EF 200mm 1.8 L USM
EF 300mm 2.8 L USM
EF 400mm 2.8 L USM
EF 400mm 2.8 L II USM
EF 500mm 4.5 L USM
EF 600mm 4 L USM
EF 1200mm 5.6 L USM
\end{quotation}
I for one really miss the focus by wire system in the super tele's anyway. I would set my 600 to the slowest setting and you could easily and accurately adjust the focus after auto focusing close on a static subject. With a moving subject you could set the MF to fast and quickly get in range of a fast moving subject so the AF wouldn't search as much. These two things can be done with todays MF but nowhere near as easy. Now all we have is the PF and I for the life of me cannot find a use for it.
An other possibility is the OM zuiko 250mm f2, fully manual, impressive wide open (though I haven't directly compared it to the Canon 200mm f1.8).
jdbastro wrote:
Well that's a bummer. Kind of what I suspected.
I imagine the FD all manual version is nearly impossible to find in excellent condition.
I guess there's always the Contax/Zeiss 200mm f2 aposonnar. It's a bit slower, and apparently not quite as sharp wide open, but available (used) and fully manual.
. given that the 200/1.8 is out of the equation for your requirement, so now comes the question
is the lens ONLY going to be used for this scope ? or were you wanting to use it on an EOS body as well ? .
If its to be used as a camera lens as well , will Manual focus be ok or would AF be a requirement ?
if its only to be used on the scope or MF is fine on a camera for you then that OM sounds a good option . (250mm F2 wow )
scout around on the Alt forum and you may come up with some other options .
as for the FD 200/1.8 I dont know what sort of availability there is (didnt most of them get taken back by canon and turned into the EF version ? or am I thinking of another lens?) but I do know that most good FD glass has priced itself very high now since the advent of the Mirrorless bodies (that FF sony will only make it worse) . in some cases ive seen FD super tele's (the 300/2.8 is a good example) go for near the same price as a good EF version which still sounds silly to me
I know for your use you'll be wanting the fastest option available but would a 200/2 a better option ? or at a pinch a much cheaper option would be the 200/2.8L (yeah 1 stop slower I know )
Do you need to be able to change focus, or is it a case of setting it at infinity focus and locking it there?
If the latter, there has to be a way. This astro sky survey project uses eight 200 f/1.8 lenses mounted to astro CCD cameras. Super WASP
Then there is this guy, who took apart his 200 f/1.8. It's mounted on an astro CCD camera, but a cable extends from the lens to a Canon body, and he uses the body to power the lens so it can focus: Astro Anarchy
