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12-29-2010, 08:18 PM   #1
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DA lens on ME camera

Just for fun I tried my DA* 200 F2.8 on an ME camera and found that the shutter speeds are a few stops too low for F2.8. Why would that be? The camera works fine with M, A and FA lenses - and shows much higher speeds for F2.8 on lenses other than the DA*.


Last edited by Spock; 12-29-2010 at 09:10 PM.
12-29-2010, 09:39 PM   #2
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The ME can only tell the lens aperture setting with a small tab in the camera mount, on the rewind crank side. It matches up wiith another tab in the lens mount, opposite the aperture lever. If you look at the mount on an M lens, you can see the tab move when you turn the aperture ring. The DA lenses have no aperture ring. They do have a pin where the M lens has a tab.

If your ME is right, that pin isn't at f2.8, the only aperture that the ME could use anyway. It seems like a compatibility mistake. But my guess is the pin is in the same place it would be if the lens had an aperture ring, and the ring was set to A. That would make the lens compatible with all the cameras that could control the lens, giving up compatibility with the bodies that couldn't.
12-29-2010, 09:41 PM   #3
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I've attempted some similar silliness with my DA35 Ltd on a KM film SLR. What I noticed was that the meter reading corresponded to the correct exposure if the lens were stopped down to its minimum aperture (F/22). I think this is because when you trip the shutter, the camera stops down the lens as far as it can before it hits the limit imposed by the aperture ring. No aperture ring, no limit, so you're shooting at the minimum aperture of the lens (F/22 in my case).

However, I'm not fully knowledgeable in such things and haven't even developed my first experimental roll of film yet. Anyone else care to support or refute this theory? I'm curious to know either way - I can live with a DA35 (or a DA200) "stuck" at F/2.8; F/22 is much less useful.
12-29-2010, 10:52 PM   #4
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Yes, that makes sense. I was only thinking about metering with the ME, which might work if the pin in the DA mount was in the right place. But on older cameras, the camera works as you say:

QuoteOriginally posted by Hello_Photo Quote
... I think this is because when you trip the shutter, the camera stops down the lens as far as it can before it hits the limit imposed by the aperture ring. No aperture ring, no limit, so you're shooting at the minimum aperture of the lens (F/22 in my case).
So metering doesn't matter much. With a DA lens on a camera with the basic K mount, you can only shoot fully stopped down. The only way I can think of to avoid that is to stuff something in the mount to keep the aperture lever wide open. You'd have to work out metering yourself. If it really thinks the lens is at f22, it's 6 stops off.

12-29-2010, 11:48 PM   #5
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The newer lenses don't fall into the compatibility claim with the older bodies, but with classic glass available in the $50+/_ range why not splurge and try a classic lens as it should be experienced with an older film body.

And the older lens will definitely be a player with your DSLRs.

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12-30-2010, 12:00 AM   #6
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I was only referring to metering as indicated by the shutter speed in the ME's viewfinder. The shutter speed is consistently too low to be correct - as if the DA* 200 lens was stopped down to F16 or F22 - and yet it appears to be wide open (f2.8) judging by the bright image in the viewfinder.

Last edited by Spock; 12-30-2010 at 05:10 AM.
12-30-2010, 06:27 AM   #7
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I don't believe the ME is compatible with the "A" setting on automatic lenses, and since the DA lens is only "A", the camera will often just shoot at f22. When you focus and compose, the lens is wide open. But when you shoot it stops right down... and it does not meter for f22 either.

It does work with any camera with an "auto" mode.... but you have to use auto mode.
12-30-2010, 06:50 AM   #8
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QuoteOriginally posted by paperbag846 Quote
I don't believe the ME is compatible with the "A" setting on automatic lenses, and since the DA lens is only "A", the camera will often just shoot at f22.
No, the ME certainly isn't compatible with lens apertures set to the 'A' setting. So, what you are saying is that although the lens is wide open while you are looking through the viewfinder, the metering is reflects that when you take a photo the camera will stop the lens down fully. Hmm... That tallies with my observations.

Thanks.

Funny how it is the exact opposite of what happens when you put a manual lens on a DSLR (ie. the only aperture available is wide open).

12-30-2010, 07:30 AM   #9
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QuoteOriginally posted by Spock Quote
Funny how it is the exact opposite of what happens when you put a manual lens on a DSLR (ie. the only aperture available is wide open).
Yes that is funny... and I haven no idea why that happens . The good news is there are a lot of old Pentax SLR's with auto settings out there on craigslist or whatever for a song. Sometimes they also come with nice lenses.
12-30-2010, 05:11 PM   #10
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QuoteOriginally posted by paperbag846 Quote
Yes that is funny... and I haven no idea why that happens
Pentax changed the way the aperture arm in the camera moved. On the original K-mount cameras, the aperture arm was either up or down. That's all that was needed; the lens was controlled by the aperture ring.

They needed to get clever when they wanted the camera body to control the aperture. On these bodies, the arm can move in precise increments. They had to change the lenses too, so the camera's arm movement translated into the correct aperture blade movement.

Getting all this to work, pretty much as designed, 25 years later on DSLRs is a pretty amazing feat.
12-30-2010, 06:13 PM   #11
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Yeah, the metering system changed between the 'M' and 'A' type lenses. The ME and other standard K-Mount cameras worked by the camera metering wide open and then mechanically calculating the number if stops of light lost between wide open and the pre-set aperture. It didn't matter what the maximum/minimum aperture of the lens was, only the loss of light mattered.

The 'A' setting repurposed the lever arm allowing the body itself to set the aperture. In order to do this, the lens had to be at its minimum aperture, the aperture lever need to be linear and electrical contacts were added to inform the camera what the minimum and maximum aperture the lens had.

In todays dSLRs, the first metering method is absent, hence the green-button mode. It's a shame because it's probably not too expensive to build support into the camera (call it legacy-Av mode!)
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