Originally posted by mistertransistor I'm a new member. I have a K-50 which I use exclusively with 'old glass', mainly Tamrons. I want to be sure that I understand what websites mean when they say that Pentax-M lenses are 'manual aperture'. I just want to confirm that this means I set the aperture using the ring, but still can focus fully open - when I shoot (and when I use the green button to determine exposure) the camera stops down. I ask because to me, 'manual aperture' sounds like the camera has no control of the iris at all.
thanks
Andrew
Manual aperture has changed over time.
Originally manual aperture required you to manually set the aperture.
This was soon replaced by automatic aperture where the camera let you focus wide open and then stopped the lens down to expose the frame, but his still required to stop down manually or metering
The next evolution was to have linkage to tell the camera what the aperture was set to (specificAlly how many stops down from wide open you were. This way you could both focus and meter wide open.
Next were lenses with the A position. This permitted the camera to set the aperture though the control of the aperture lever and based upon knowledge of the lens maximum and minimum aperture from the contacts.
Today this is what people refer to as automatic aperture
Sadly for you. The M seri s l need lack the contacts to l t the camera set he aperture. So you n the d to use the green button