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10-15-2008, 06:57 AM   #16
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QuoteOriginally posted by KungPOW Quote
Why is there no such thing as a stupid question?

Actually there is one really stupid question.

The one that someone should have asked, but didn't!

All others really just identify the persons level of knowledge, level of comfort with a sjubect, or experience. We should not pick on people because they don't share the same level as us on any of these points.

10-19-2008, 02:33 PM   #17
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QuoteOriginally posted by lithos Quote
The K mount is an auto stopdown mount. The protruding lever on the lens mount is held open by a corresponding lever in the camera's mount. Basically, when the shutter's fired, the camera let's that protruding lever go, letting the lens lever spring open, stopping down the lens.

Now, no, the ME Super doesn't require dead-reckoning metering. Like most modern lens mounts, the aperture setting of the lens is conveyed to the camera. (Jeez, what kinda camera did you think it was - not having open-aperture metering indeed!)

This is done with the other lever on the lens - the recessed one. If you look at the back of the lens, you'll notice that the this lever moves when you change the aperture. This interfaces with another lever on the camera's mount, which moves with the lens's recessed lever. This tells the camera - and, more importantly, the meter - what aperture the lens is set at. The meter then compensates for it.

Remember, an f-stop is an f-stop is an f-stop: with lenses of varying focal lengths and types set at the same aperture, the amount of light reaching the meter and the film is always the same. A 1200mm reflex lens at f11 transmits the same amount of light as a 16mm fisheye set at f11 which transmits the same amount of light as a 50mm lens set at f11 as a 100mm macro set at f11...well, you get the idea.

Lenses from the A, F, and FA series have the ability to transmit aperture info to the camera via a electrical contacts in the lens's mount. This also works the other way, too - cameras from the A, P, SF, Z/PZ, MZ/ZX, *ist and the digis can tell those lenses what aperture to use (well, not really - they just set the lens at its minimum aperture and then stop it when it reaches the desired f stop.)

The *ist series and later are only able to work with purely manual lenses by means of stop-down metering - they lack the lever on the lens mount that meshes with the recessed lever on the lens.

I know I'm being longwinded, and I apologise if I come across as condescending, but I think people should know the why and how as well as the yes and no.
a very thorough answer, thanks
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