Is there life after aperture block failure?

Massao wrote:

Futax wrote:

Good grief, this is getting tedious!

No doubt. Can you please make a video of your miraculous camera that can change apertures on adapted lenses like Adaptall 2 and M42? You have a special camera that everyone must buy.

In Av mode the camera needs to know the aperture to which the lens has been set, because it does the metering with the lens wide open.

How on earth your camera makes an adapted lens WIDE-OPEN?

With a modern lens, it knows both apertures (wide-open and set-aperture), so can do the calculation for correct exposure. With a legacy lens, it doesn't - and there's no way of telling the camera explicitly - you have to fool it.

I never said anything about painting the "rear element" black! That was a reference to the fact that most (all?) M42 lenses have non-conductive rears. Whereas most K-mount lenses have bare aluminium conductive rears. And the discussion about Av mode above requires lenses with conductive rears.

To do what? The light reaching the mirror/sensor is coming from the glass elements, not lens mount--unless the lens is not mounted properly or some other issue with adapter/mount.

Look - I'm talking about the base of the lens - which by and large is silver for a K lens and black for an M42 lens. Is that so difficult to understand?

So other than the magical play with changing aperture on adapted lenses, there is some conduction, and some silver vs black paint difference making it even more miraculous. Sure, I got it completely. This is fascinating stuff You are on a brink of a new scientific discovery. Seriously!

What the hell are you talking about?  Please read what I'm say and try to understand.  If English is not your first language, then that might explain things.  A modern DSLR has electrical contacts which mate with contacts on the base of a modern lens.  The camera can deduce certain things when the camera has a conductive base, and when it has an non-conductive base.

A non K-mount lens (e.g. M42) can't be stopped down automatically - I never said differently.  A K-mount lens with a black base will behave differently, so none of what I've been saying will apply to these either.  (You can scrape the finish off in the right area though).

If you don't want to bother with Av mode and exposure compensation, then stick to "M" mode and the green button.

M mode works fine and so does A-priority mode. The only difference is you do not need to press the green button in Av mode.

Av mode does NOT work fine with an aperture-ring lens. Unless you have a "good" K-50 and have set the aperture ring to the "A" position, if it has one.

Unless you fool the camera using exposure compensation.

Av mode works fine on Pentax DSLR's when using adapted lenses without any need for exposure compensation. Unless, the camera is owned by pseudo-scientists that make up new things and concepts to ignore the basic fact that they are not able to understand and apply the simple process of taking a well-exposed image with an adapted lens.

Av mode DOES NOT work fine.  With most Pentax camera models, the aperture you set is not applied.  Exposure may look OK, but all shots you take are taken with a wide open aperture.  It doesn't stop down.  Unless you have a K-50, which DOES stop down but will underexpose if left to its own devices.

But you'll probably get inconsistent exposures, with no two lenses behaving identically with a variety of apertures.

Not in my experience! Two identical lenses will perform identically!

I'm not talking about identical lenses - I'm talking about different lenses which might be set to the same aperture. Also, any given lens set to various apertures. As I say, you're lucky if you get consistent exposure with stop-down metering.

Alright, too many new theories already. That's enough for a day. The nobel prize can wait

I see we have a smart alec in our midst.

Note: my suggested use of Av mode may well not work with other Pentax models, but it does with the K-50 (at least it does with mine).

That I can agree on I don't know what kind of settings you have changed on your camera, but my sincere suggestion is to: 1) reset the camera; 2) change the necessary settings as recommended by PFhere , and; 3) try your manual lenses again. Also check that your manual lens actually changes the aperture when you stop it down. As long as you are using exposure compensation to properly expose an image, something is wrong with your setup! Simple as that!

I don't WANT to change - Av mode isn't MEANT to work with legacy lenses.

Don't you see - this is a useful undocumented feature of the K-50 which helps make up for its otherwise disgraceful failure mode.

Yes, what a discovery. I'm cheering for you already. Can't wait for this to reach the press. You rock!

I'm afraid sarcasm attempts serve only make you look more foolish.