Pentax K-7 Operating Manual page 106

Youcansetboththedesired shutter s peed andaperture t otakethe
picture.
Automatically setsthesensitivity s othatthe manually s etshutter s peed
andaperture willgivetheproper e xposure according t othebrightness o f
thesubject.
I Set the mode dial to TAv.
2
Turn the front e-dial (.,'_,.) to
adjust the shutter speed.
The shutter speed can be set within the
range of 1/8000 to 30 seconds.
3
Turn the rear e-dial (;,,_,,_) to
adjust the aperture.
Aperture range depends on the lens in
use.