Jörg Krüger
Pentax ES
Pentax ES "Electro Spotmatic" from 1971, first Pentax with electronic shutter and full-aperture metering, probably the first SLR offering aperture-priority AE at all.
For full-aperture metering there must be a coupling between lens and camera, so that the camera can read out the set f-stop. The Pentax lenses with that coupling for the M42 thread mount are called "Super-Multi-Coated Takumar" or "SMC Takumar". As far as I know there are only three cameras which make use of this coupling: ES, ES II and Spotmatic F. Those lenses have an auto/manual switch (in manual mode the lens is always stopped-down), if such a lens is attached to an ES (or ES II, SP F) you can't trip this switch from auto to manual.
As mentioned above, the ES provides an aperture-priority AE mode: you set an f-stop and then the camera selects a shutter speed, which is shown in the viewer when you press the shutter button half-way. In manual mode the shutter is working fully mechanically (without a battery), but you have only fast shutter speeds (1/60 up to 1/1000) and B and the light meter is switched off. I think this is why some people don't like this camera.
Automatic exposure also works with other M42 lenses than the SMC lenses, but only stopped-down of course (lever near the lens mount).
The camera needs one PX 28 battery (6 V). I think you can use four SR44 button cells with some tape for isolation instead. If you press the small button beside the rewind crank the battery power is checked: the needle for the shutter speed should move from 1/1000 to at least 1/30.
Pentax ES
Pentax ES "Electro Spotmatic" from 1971, first Pentax with electronic shutter and full-aperture metering, probably the first SLR offering aperture-priority AE at all.
For full-aperture metering there must be a coupling between lens and camera, so that the camera can read out the set f-stop. The Pentax lenses with that coupling for the M42 thread mount are called "Super-Multi-Coated Takumar" or "SMC Takumar". As far as I know there are only three cameras which make use of this coupling: ES, ES II and Spotmatic F. Those lenses have an auto/manual switch (in manual mode the lens is always stopped-down), if such a lens is attached to an ES (or ES II, SP F) you can't trip this switch from auto to manual.
As mentioned above, the ES provides an aperture-priority AE mode: you set an f-stop and then the camera selects a shutter speed, which is shown in the viewer when you press the shutter button half-way. In manual mode the shutter is working fully mechanically (without a battery), but you have only fast shutter speeds (1/60 up to 1/1000) and B and the light meter is switched off. I think this is why some people don't like this camera.
Automatic exposure also works with other M42 lenses than the SMC lenses, but only stopped-down of course (lever near the lens mount).
The camera needs one PX 28 battery (6 V). I think you can use four SR44 button cells with some tape for isolation instead. If you press the small button beside the rewind crank the battery power is checked: the needle for the shutter speed should move from 1/1000 to at least 1/30.