Pentax ES - Open-Aperture or Stop-Down Reading

Asahi Pentax ES Operating Manual Excerpts
Reproduced for Historical and Reference Purposes by Paul M. Provencher
http://whitemetal.com Not For Resale.
13
OPEN-APERTURE
OR STOP-DOWN READING
With the new Super-Multi-Coated (SMC) Takumar
lenses with an open-aperture reading pin (1),
mounted directly on the ES camera body, the TTL
meter reads exposure through the fully open
aperture or stopped-down taking aperture for
correct automatic exposure. For open-aperture
reading, the stop-down lever should be DOWN; for
stop-down reading, push up the lever.
With all other lenses or when using Extension
Tubes, Bellows Unit or Microscope Adapter,
remember always to push up the stop-down lever
for stopped-down aperture reading and correct
exposure.
The SMC Takumar 85mm f/1.9 (photo at the top
right) and SMC Takumar-Zoom 85mm~210mm
lenses do not have the open aperture reading pin
(1), and therefore, they should be used on the ES
for stop-down reading.
Also remember that the TTL metering does not
work unless the shutter dial is set at "AUTOMATIC".