This question is related to the Canon 200mm f/2.0 lens.
Does focusing work by moving the black rubber focusing ring
if the lens is in manual focus mode AND IF there is no
canon body attached to the end of the lens (i.e. it is not
Say I want to project a source in an optical lab with this lens onto a detector,
and want to use it in fully manual focus mode.
This did not work with the Canon 200 f/1.8 AF lenses.
On external focusing Canon lens, the focus works when set to MF whether it is attached to the camera or not. On internal focusing lenses, it is not readily apparent. Because they don't change their length. I would guess they will, however, since the MF just connects the focus ring to the lens mechanically.
Thanks for your response.
You say "on external focusing Canon lens" the focus works when set to MF.
The Canon 200 f/2 counts as an "external focusing lens"?
I am asking this, because the manual focusing definitely does not work
on the older Canon 200 f/1.8L USM lens, even when turned to MF mode, but
without a Canon camera attached. So I guess with your definition the 200/1.8 is
not an external focusing lens. When a Canon body is attached to the 200/1.8,
then the MF works fine, but one needs to power up the lens and its CPU so that
it converts the motion of the rubber ring into electronics, and ultimately motion
of internal lens elements.
I understand that this is not a standard use of the lens, so hoping that
Canon afficionados will know this. Clearly, the lens does not change
its outer dimensions while focusing. But one can see the focus changes
when projecting e.g. a landscape on a piece of white paper.
I do not have this lens but I have a photographer buddy that does, so I asked him. Here is what he said;
The internal-focusing lens does not extend and does not rotate the front element as most fixed focal length lenses do not extend. It has FTM (Full Time Manual) focusing.
But he did not know whether it worked without the camera attached.