Originally posted by blink However when I press the green button this also activates the shutter? Is that correct?
No, it activates the aperture blades in the lens. When you take photos, here are the sounds you hear:
- Shake reduction
- aperture blades moving to the selected aperture
- mirror snapping up
- Shutter opening
And then it goes in reverse, with these things closing. Green button by default just closes the aperture blades and takes a metering reading, then adjusts shutter speed. But you can customize the green button to do something else (this button is a Pentax specialty). If you customize it to do DoF preview, it will move the aperture blades down and keep them there for you to see the photo.
Anyway, if your lens has A setting on aperture ring (usually have to press a little button to choose it), you don't need to use the green button. Just select Av or P mode on camera and go hog wild taking photos! You choose the aperture on the camera body, or in automatic modes, the camera does that for you. DA lenses are basically constantly in A-mode, this is why many of them don't even have aperture ring anymore.