CANON EOS and M42 adapter with electronics for manual lenses

Archived from groups: rec.photo.digital.slr-systems,rec.photo.equipment.35mm (More info?)

Marek C posted:
> Hi,
>
> I made an M42 adapter to be able to use old M42 lenses with CANON EOS.
> I attached electric contacts and electronics from old 28-90 zoom lens
> to get the focus confirmation. The problem is that it doesn't work
> very well. The AF circuit in the camera sees everything like it would
> be closer than it is normally. I mean that if the proper distance is
> 15 meters, AF gives the focus confirmation at 10 meters. Everything is
> a little blurred. I have better results using my eyes than
> electronics. I made many tests with EOS analog and digital cameras
> (EOS 300 or 300D) and the SONNAR 135/3.5 lens.
>
> Maybe in the electronic circuit there are some lens characteristics
> that becomes invalid when I swap optics. Anybody has any idea?
>
> Marek
> (macop@poczta.onet.pl)
>
Czesc!

It could be that the camera isn't taking into account the thickness of
the adapter ring and setting focus according to some preset value (off
by this much, compensate by this much) or not using a TTL focusing
system. You should try different focusing settings, but I think you may
have to just focus manually.

Pozdrawiam,

--
Petros
Ap' ola prin ipirche o Logos

Archived from groups: rec.photo.digital.slr-systems,rec.photo.equipment.35mm (More info?)

macop@poczta.onet.pl (Marek C) writes:

>> It could be that the camera isn't taking into account the thickness of
>> the adapter ring and setting focus according to some preset value (off
>> by this much, compensate by this much) or not using a TTL focusing
>
> All SLR cameras are using TTL focusing. Anyway, I cannot imagine any
> modern camera that doesn't focus through lens.

Have you heard of the Leica M series?
--
David Dyer-Bennet, <mailtod-b@dd-b.net>, <http://www.dd-b.net/dd-b/>
RKBA: <http://noguns-nomoney.com/> <http://www.dd-b.net/carry/>
Pics: <http://dd-b.lighthunters.net/> <http://www.dd-b.net/dd-b/SnapshotAlbum/>
Dragaera/Steven Brust: <http://dragaera.info/>

Archived from groups: rec.photo.digital.slr-systems,rec.photo.equipment.35mm (More info?)

"FG" <fergor_togliquesto_@libero.it> writes:

> Hi Maek,
> I tryed years ago to do the same thing... but I didn't find the time to
> assembly the parts...
> It's strange the camera see wrong focus distance... in particular EOS 300...
> Have you switched in manual focus your M42 device ?

I don't think there ever was an autofocus M42 lens.

<snip>

>
> Marek C <macop@poczta.onet.pl> wrote in message
> 17b5b4a1.0411060602.151cfb43@posting.google.com...
> > Hi,
> >
> > I made an M42 adapter to be able to use old M42 lenses with CANON EOS.
> > I attached electric contacts and electronics from old 28-90 zoom lens
> > to get the focus confirmation. The problem is that it doesn't work
> > very well. The AF circuit in the camera sees everything like it would
> > be closer than it is normally. I mean that if the proper distance is
> > 15 meters, AF gives the focus confirmation at 10 meters. Everything is
> > a little blurred. I have better results using my eyes than
> > electronics. I made many tests with EOS analog and digital cameras
> > (EOS 300 or 300D) and the SONNAR 135/3.5 lens.
> >
> > Maybe in the electronic circuit there are some lens characteristics
> > that becomes invalid when I swap optics. Anybody has any idea?

Well, in the old days, lenses like thread-mount Takumars all had a
little red infrared focus mark somewhere along the depth-of-field
scale. The idea was that the lens wasn't chromatically corrected for
infrared, but you could make it work by focusing visually, then moving
that focus point to line up with the IR focus mark. Since, as far as I
know, the autofocus sensor operates in the near IR, is it possible
that this focus shift is the problem? I don't know if modern AF lenses
are corrected better so the focus shift doesn't matter, or perhaps
they are designed to have the same shift for all lenses, or maybe each
lens signals the camera with its focus shift so the AF circuitry can
correct for it.

--
-Stephen H. Westin
Any information or opinions in this message are mine: they do not
represent the position of Cornell University or any of its sponsors.