Originally posted by lindseyd I have a Pentax K-70. I've set up back button focus (AF2). How do I meter now? Will I still be able to see the * in the viewfinder?
The back AF setup is not for metering. It is for focusing- Auto Focus to be specific. But the button is alternately used as an AE-L button instead of a back AF button. In that case, it also does not meter, but it will lock the exposure meter that has been set already by metering. This is used under various conditions where a metered value is needed to be preserved, while lighting situations may be changing. When the button is set for that use, then you get your AF via the front shutter release button by using the half/press to obtain AF and to hold focus.
Metering takes place in a manner according to where you have set your mode dial. If you want your camera set for fully automatic exposure metering, where both the shutter speed and the aperture will be set by the camera according to the camera's meter reading of the lighting, then the mode dial can be set either on the green AUTO mode, or on the "P" mode. The "P" mode is better because the green AUTO mode does not allow access to many adjustments and to many control features, including the exclusive Pentax Hyper Program operation, where you can override the camera's setting of either aperture or shutter speed. You can also have the camera automatically adjust the ISO according to the light meter reading as well in this mode.
There are other automatic exposure metering modes on the mode dial to choose from, which are not fully automatic because you play a role, such as selecting a preference of aperture or shutter speed, while the camera automatically compensates by setting the other. These are the Tv or Av modes. Consult your handbook for the other modes. There are good reasons for being able to take control of these aspects of photography instead of always just having your camera on auto-pilot.