Metering and 'auto' lenses

[thecornflake]

So I'm getting confused here with in-camera metering on my film SLR (Fujica AZ-1) and lenses with an auto setting. The auto setting means the aperture is always stopped down to whatever the setting is on the lens all the time. With it on the meter clearly has different results than when the lens is set to manual. However I don't normally meter with the DOF pressed down. So I'm not sure how the auto setting should be used?

 

[s162216]

Are you using the dedicated Fujinon lenses on it? The Fujica AZ-1 used M42 screwmount lenses, but the dedicated lenses also have a special linkage to the camera allowing it to read the aperture at which the lens is set, thus allowing open aperture metering when the camera is set on auto (essentially aperture priority). Non dedicated lenses however don't have this linkage so when the camera is set on auto, the camera has to meter with them stopped down (as further described below you need to set the lens on manual to use the cameras auto mode).

On M42 lenses all that the auto setting does is keep the aperture open whilst focusing, and (on suitable M42 cameras - most after the late 1950's) when you press the shutter a little 'kicker' pushes on a pin on the lenses mount which stops the lens down at the time of taking the picture; setting the lens to the 'manual' setting just keeps it stopped down.

Link to the Fujica AZ-1 manual here: http://www.butkus.org/chinon/fujica/fujica_az1/fujica_az-1.htm

 

[thecornflake]

I have a Zeiss lens with manual\auto switch, a Takumar lens with the same and also Fujinon\Takumar lenses without the switch (but with the push pin).

I'm also guessing the lens is in auto mode when the word Auto is covered by it? (sorry if that's a really stupid question).

 

[s162216]

Its easy to tell, dismount the lens, set it to f11 or 16 and look through it, if the iris is stopped down then its in manual, if not then its set to auto. Lenses without a switch are auto only, which in makes it not possible to use them with the auto setting on the camera (unless its one of the Fujinon lenses with the linkage). To my knowledge though all Pentax Takumar's have an auto/manual setting (except manual only ones, typically long telephotos).

 

[thecornflake]

Ok, so if it's a Takumar (with the little pin) with a switch to use AE I should set it to auto but the Zeiss needs to be set to manual?

 

[s162216]

No, (Pentax) Takumars cannot be used as they lack the linkage to the camera to indicate the aperture (although some types do have their own version to link up with certain Pentax cameras). Only the dedicated Fujinon M42 lenses (list here: http://www.pentax-manuals.com/fujica/fujica.htm ) have the linkages so to use the camera in auto so any other M42 lenses (except for the Fujinon lenses - which should be set to auto to allow the camera to function properly in AE) must be set to manual to use, or be set in auto and used on one of the cameras manual shutter speed settings.

 

[Steve Smith]

No, (Pentax) Takumars cannot be used as they lack the linkage to the camera to indicate the aperture

I know it's a minor point, but usually with cameras which meter with the lens wide open, all the linkage from the lens does is tell the camera how many stops from wide open the aperture setting is so the meter can compensate. The actual aperture f No. does not matter.

e.g. an f2.8 lens stopped down to f5.6 needs the meter to adjust for two stops of light. As does an f4 lens set to f8.


Steve.

 

[thecornflake]

No, (Pentax) Takumars cannot be used as they lack the linkage to the camera to indicate the aperture.

Sorry - actually meant Fujinon when I said Takumar. So basically 'auto' means the meter automatically compensates for the aperture in AE mode, but only works like this with the lenses that have the appropriate bit (i.e. the pin).

 

[s162216]

The actual 'pin' is on most M42 lenses as you can see on the upper part of this picture (from Wikipedia):

All it does is stop down the lens when the picture is taken (and the lens is set in auto), thats it and that functions with most M42 cameras. If your using a non-Fujinon M42 lens and you want to use the Fujica on AE then you have to dis-enage the auto setting on the lens (it may be auto only - a lot of cheaper later ones were) so it will be always stopped down to the aperture set and the camera can read the light coming through. The Fujinon M42 lenses however have an additional pin, lug etc (I can't find a suitable picture of the rear of one to find out how it does it) that allows it to communicate to the camera what its set to so the camera can meter with it wide open on AE, because of this you should leave the Fujinon lenses on auto.

The Pentax M42 open aperture metering system was quite similar, if you look on the left of the picture linked below you can see the pin to stop the aperture down as on the above picture, but also on the right a wider 'flange', its that flange which indicates the aperture to the camera.

http://www.grainlab.com/images/m42_smc_taku_14-50_3b.jpg