Is there life after aperture block failure?

Massao wrote:

Futax wrote:

Massao wrote:

Futax wrote:

If you're using M42 lenses, they'll almost certainly have black anodised rears. This means you have to use stop-down metering (and you can't use Catch-in-Focus). With the K-50, it seems that you can use Av mode (as well as Catch-in-Focus) - with most K-mount lenses. That's because they mostly have bare metal rears. The camera will detect the conductive rear, and act accordingly.

Not sure if black anodised vs conductive rear theory is correct, but anynow I have not noticed any difference in metering based on this difference.

Aperture block failure just means the camera can't stop down an "A" type lens (i.e those without an aperture ring, or one which has been set to "A") to the correct aperture

Correct :-)..

And since the camera doesn't know what aperture you set - it'll assume wide-open - you have to compensate using EV compensation.

Not correct. The camera does not know what "wide-open" is either. With fully manual old lenses (like M42), the camera has no idea of knowing what the smallest F value/widest aperture lens offers.

The camera doesn't know what aperture it's shooting at, but it assumes the lens is set to the same aperture as when it does the metering - i.e. wide-open in Av mode. It will expose accordingly unless instructed differently.

You are mixing everything here. If you set the aperture (on the aperture ring) on ANY non-PK mount lens like M42 or Adaptall 2 lens and set M on lens (which implies: any change in aperture is evident immediatly) then there is no way a camera can EVER know anything about wide-open. The only thing camera sees is through the stopped-down lens. Seriously, what is so complicated about this?

You really don't understand what I'm saying.  The camera assumes the same aperture as when it did the metering - and with a K-mount lens, that 's wide-open.  It realises it doesn't know anything about shooting aperture, so assumes the same aperture.

The cameras metering system sees only what you show to it, i.e., by stopping down the aperture ON the lens, i.e., rotating the aperture ring and selecting manual mode ON the lens.

The metering in Av mode is done before the shot is taken, so the lens is wide open. The camera has no knowledge of how much the lens will be stopped down when it takes the shot.

Are you trying to convince me that your pentax camera can literally change aperture on all non-PK mount lenses with adapters? The wholegame about wide open and then camera stopping it down implies it.

What on earth are you talking about?  I'm talking about K-mount lenses in Av mode - nothing more, nothing less.  How the hell can a non-PK lens be stopped down?

So, when you set the aperture on your m42 lens or other lenses with adapters (M mode on lens) and then take a picture with it in Av mode (on camera), the camera first magically changes the aperture on your manual non-PK mount lens to wide-open then notes the exposure, and then applies that exposure again while magicallystopping down your non-PK lens? I need your camera. We all do

What on earth are you talking about?  Suggest you read what I'm saying, and then read it again.

There is absolutely no need to use EV compensation when using any manual lens on Pentax DLR's--unless you are trying to under or over- expose an image intentionally.

You can't even use exposure compensation in M mode - which is what you would normally use for aperture-ring lenses (You modify the shutter speed using the thumbwheel if you want to intentionally over/under expose).

But I'm talking about use of Av mode.

You don't have to use Av mode - you can use M mode, but it does have its shortcomings.

So, to wrap up: 1) M mode (on camera) despite pressing the green button does not exposes properly, and; 2) in Av mode, it till does not expose properly which is why you use exposure compensation? There is something seriously wrong with your camera!

M mode is inconsistent (as is well known).  There is actually something wrong with your understanding of the problem.  Av mode is not meant to work at all with legacy K-mount lenses (it's not meant to stop down at all), so you're stuck with working at maximum aperture (lowest f-number) all the time.  But with the K-50, it WILL stop down, so you just need to get it to provide the correct exposure.