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07-31-2012, 12:40 PM   #31
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QuoteOriginally posted by Moo Quote
Very interesting. It's m1 and m2 that are missing, the ones that would determine the minimum aperture on an A lens.
I agree... As they removed other contacts for this camera, and it doesn't support the old lenses, it follows that the remaining pins must be necessary in one way or another for "digital" F lenses.
Its many years ago, so memory may be wrong, that I opened a pentax A3, there these contacts were present in the bayonet, but internally not connected, so this is not new for the MZ-60, and did obviously not prevent the use of A lenses in program mode.

EDIT: I refreshed my memory, and the pentax A3 only uses the two minimum aperture contacts and not the aperture range, now I am puzzled, how it can use program mode.


Last edited by glasbak; 07-31-2012 at 01:37 PM.
07-31-2012, 01:57 PM   #32
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"This body does not support all features of the KA mount. Although the lens mount features all six contacts, the r1, r2 and r3 contacts are not connected internally. Thus the body can only determine the smallest lens aperture, but not the aperture range. This is probably the reason why the body does not feature aperture indication in the viewfinder." (Bojidar's page)
Interesting. I'm not sure either...
07-31-2012, 02:12 PM   #33
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QuoteOriginally posted by Moo Quote
"This body does not support all features of the KA mount. Although the lens mount features all six contacts, the r1, r2 and r3 contacts are not connected internally. Thus the body can only determine the smallest lens aperture, but not the aperture range. This is probably the reason why the body does not feature aperture indication in the viewfinder." (Bojidar's page)
Interesting. I'm not sure either...
Yeah, he got that from me.
Looks like my memory is fading
07-31-2012, 02:13 PM   #34
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QuoteOriginally posted by glasbak Quote
Its many years ago, so memory may be wrong, that I opened a pentax A3, there these contacts were present in the bayonet, but internally not connected, so this is not new for the MZ-60, and did obviously not prevent the use of A lenses in program mode.

EDIT: I refreshed my memory, and the pentax A3 only uses the two minimum aperture contacts and not the aperture range, now I am puzzled, how it can use program mode.
There's no problem providing program mode with only the A pin. You have to either assume the minimal aperture range (5 stops), or maybe that overexposure from overestimating the range is ok. And of course, you can't show the user the selected aperture, as it's only known in relative terms.

Re-metering after stopping down would allow adjusting the shutter speed if the lens didn't stop down as much as expected. Doesn't sound like the kind of thing they'd do on a camera this cheap though.

What I can't understand is why it would bother to check the smallest aperture. Maybe to be more aggressive about stopping down lenses with a bigger minimum aperture, on the assumption that they are faster.

07-31-2012, 02:23 PM   #35
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Got it, the A3 program mode I think.
The aperture simulator holds the aperture range information when the aperture ring is in the A position, and the two contacts the minimum aperture,
Which raises the question, why is the aperture range in the A contacts encoded, maybe more accurate than the aperture simulator readout ?.
07-31-2012, 02:28 PM   #36
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QuoteOriginally posted by drougge Quote
You have to either assume the minimal aperture range (5 stops),
Heh, yes, after making a little diagram of it, I saw this too. Never stop down more than 5 stops and it should work on any lens. But wouldn't really need even those two pins if it were just this simple...?
07-31-2012, 02:32 PM   #37
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QuoteOriginally posted by glasbak Quote
The aperture simulator holds the aperture range information when the aperture ring is in the A position,
Isn't this minimum aperture too?
(Where does "aperture simulator" come from anyway?)
07-31-2012, 02:36 PM   #38
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QuoteOriginally posted by Moo Quote
Isn't this minimum aperture too?
(Where does "aperture simulator" come from anyway?)
The aperture simulator does not tell the minimum aperture, it tels the body how much difference there will be between lens open, and the aperture closed situation, and thus simulates a lens closed metering.

07-31-2012, 03:21 PM   #39
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QuoteOriginally posted by glasbak Quote
Got it, the A3 program mode I think.
The aperture simulator holds the aperture range information when the aperture ring is in the A position, and the two contacts the minimum aperture,
Which raises the question, why is the aperture range in the A contacts encoded, maybe more accurate than the aperture simulator readout ?.
You're right! I blame the "modern" cameras for not seeing this. (Which is just misdirection, I didn't see it because my thinking wasn't strong enough.)

I suspect they did it all digitally because some people just don't like non-digital things. The aperture simulator moves quite far per click, there should be no problem reading it accurately.
07-31-2012, 04:04 PM   #40
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Hmmmmm.... Oh yes, it's not the actual stopped down aperture, but how far it has been stopped down. So knowing the minimum aperture and the range of the lens, it could determine the maximum aperture too... Yet it doesn't display an actual aperture value? Maybe just budget rather than physical limitation then?
And yes, if a camera can determine the aperture range this way, why the other contacts too?
Edit: Hmm yes, maybe even back when they designed the A mount, they were planning on "crippling" the mount at some point in the future.
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