Thanks Kosu,
Received yesterday. Expertly packed. Never received a parcel so professionally packed before.

Camera in excellent condition and exactly as described. Can tell equipment has been taken great care of.

Thanks again for such a pleasant purchase.
Mike

PM sent.

Hi John,
I too looked at your Picasa photos. Amazing pictures of Yangshou, China. I did almost the same trip there backpacking about 20 years ago. One of the most atmospheric places I've ever been. It brought back a lot of memories, thanks.
I spent quite a while in S.Korea. No-one ever goes there, and you never see any photos from that most undiscovered place.
Welcome to the forum.

Hi everyone,

I'm hoping someone can explain to me how a DSLR camera calculates exposure when using a "Pentax-A" KA mount lens.
I have a Pentax-KR and am using a "Pentax-A" 50mm f2 lens.

The below is my understanding of various configurations.

Using modern KAF2 lens with contacts on the lens
The lens contacts communicate the minimum and maximum aperture settings of the lens to the camera. At half-press of the shutter release the camera reads the light level at the "viewing" aperture (i.e. wide open) and can therefore calculate the required exposure for the "taking" aperture (i.e. stopped down to required f-stop) when the actual shutter is released.

Using "Pentax-A" KA mount lens set at a specific aperture
When an aperture is set on the lens, the camera doesn't know what aperture the lens is set at. Therefore with the camera set to Manual (and the "Green Button" function "Action in M Mode" set to "Tv Shift" ) to take the exposure you first need to press the Green Button. This stops the aperture down to the "taking" aperture, reads the light level, and adjusts the shutter speed for you.

Using "Pentax-A" KA mount lens set to Auto "A" aperture
When the aperture is set to "A" on the lens, the camera controls the lens aperture. Light reading is taken at "viewing" aperture on half-press of the shutter release button. The exposure for the "taking" aperture is calculated based on the difference between the "viewing" and "taking" aperture.

Question is: For "A" aperture, how can the camera calculate the exposure if the "viewing" aperture value is not known?

I was reading up about the contacts in the following http://kmp.bdimitrov.de/technology/K-mount/Ka.html and thought maybe that since the camera's contacts would all be touching the bare metal of the KA mount it would register as a lens contact pattern 111x11 which relates to an f1.2~f22 lens. Does this mean my camera thinks my lens is f1.2 wide-open (1.5 stops faster than my actual lens)?

I took few test shots and compared setting a specific aperture on the lens with setting the "A" lens aperture and setting the camera to the same aperture. There does seem to be a difference, typically the "A" aperture gives about 1 stop less exposure.

What do you think? Do others have differences between manual and auto settings? Am I barking up the wrong tree?

Cheers,

Hello everyone,

I first started SLR photography when I was a teenager, 30 years ago. Back then I managed to earn enough to buy something from Dixons instead of just looking in the windows. A Chinon I think it was, other choices could have been a Ricoh or a Praktica; a Pentax K1000 was just a dream.

I remember I also later bought a 28mm and a 135mm lens, 2x converter and extension tubes. I used to do my own B&W negs and prints in a spare room I converted into a dark room. Kept me busy for quite a few years.

I've recently returned to the world of SLR with a Pentax KR with kit lenses and must say I'm very impressed with the whole kit. A lot easier to use than my ancient SLR but still just as challenging to produce a decent photo (for me).

Funny though the prices of most lenses still seem just as high as they did when I was a teenager. Some things never change. It's amazing the progress from film to digital and how much can be done so quickly compared to the old days; now if I only had the same amount of time as I did then...

Enjoying the forums, there are some very talented people on here and some great info. Hope everyone keeps it up. I'm sure there are many people out there, like me, who appreciate the time others take in sharing their knowledge and experience.

Cheers,

I'm interested in the PK Aico extension tube set. Is it still available?