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02-20-2009, 11:54 AM   #1
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Stopping down manual lenses on k2000?

I have some FF lenses I would like to get to meter correctly with the k2000/k-m. I have set the option in the menu to allow for the aperture ring to be used. I also set the AF button the k2000 to AE-L so I can stop down.

When I take the lens off of A mode using the aperture ring, and then press the AE-L button, nothing happens at all. Usually, when I press it not using the aperture ring, it will lock in that exposure (shows a * in the VF) to allow the camera to change aperture and shutter speed proportionally. I have tried just pressing the AE-L with and without half pressing the shutter button, but nothing happens at all. What am i doing wrong?

02-20-2009, 01:00 PM   #2
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I don't have my K-m in front of me, but I believe you can configure the exposure "+/-" button to do the stop-down metering with manual lenses.
02-20-2009, 01:58 PM   #3
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On my K100D, you have to have the camera in "M" mode for the "AE-L" button to do stop-down metering. Additionally, pressing "AE-L" will not turn on the meter, you have to bump the shutter button first.

So to state that in reverse, and potentially more coherent order:

1 - Put the camera in "M" mode, not Tv, not Av, but "M"
2 - Tap the shutter button half way, to activate the light meter
and then, before the meter turns off (3-30 seconds, whatever you have it set to)
3 - Hit AE-L
02-20-2009, 04:14 PM   #4
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I'm an old film SLR guy learning the ins and outs of DSLR and all the terminology, so please forgive me if I misunderstand.

While in M mode I don't understand the point of AE-L. Why do you need to lock anything when the settings are all manual? They're basically locked until you change them.

I just tested things out on my K2000. I configured the AF button to AE-L as eyou stated and noticed the AE-L would work on all modes except for M. This makes sense since in M nothing changes unless you either manually change it or use the AV button to meter.

What I've been doing with my manual lenses:

M Mode: Set Aperture, press AV to meter, shoot
Av Mode: Set Aperture, shoot

02-20-2009, 04:27 PM   #5
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QuoteOriginally posted by wasser Quote
While in M mode I don't understand the point of AE-L. Why do you need to lock anything when the settings are all manual? They're basically locked until you change them.
Right. And since the usual purpose of the AE-L button does not exist in M mode, that's why they chose this button to perform the completely unrelated task it performs in M mode: to stop down the lens momentarily, meter, and set an appropriate shutter speed. At least AE-L was the button chosen for this task on the DS, DL, and K100D. On other models it is the Green button. And on the K2000, it is apparently the Av +/- button, if you have it configured that way?

QuoteQuote:
What I've been doing with my manual lenses:

M Mode: Set Aperture, press AV to meter, shoot
Av Mode: Set Aperture, shoot
In Av mode on a fully manual lens (eg, no "A" position on aperture ring), the aperture ring is completely ignored - it always shoots wide open. It sets a correct shutter speed for wide open shooting, so you get well-exposed pictures every time, but they're actually being shot all wide open.
02-20-2009, 05:21 PM   #6
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QuoteOriginally posted by Marc Sabatella Quote
Right. And since the usual purpose of the AE-L button does not exist in M mode, that's why they chose this button to perform the completely unrelated task it performs in M mode: to stop down the lens momentarily, meter, and set an appropriate shutter speed. At least AE-L was the button chosen for this task on the DS, DL, and K100D. On other models it is the Green button. And on the K2000, it is apparently the Av +/- button, if you have it configured that way?
Ahh...so the AE-L = Meter in these other cameras.

On the k2000/k-m the Av defaults to meter. At least I'm pretty sure it does since I'm not even aware if there is a way to manually configure the Av button. I suppose it was automatically configured that way I adjusted the setting to use the manual aperture ring).

QuoteQuote:
In Av mode on a fully manual lens (eg, no "A" position on aperture ring), the aperture ring is completely ignored - it always shoots wide open. It sets a correct shutter speed for wide open shooting, so you get well-exposed pictures every time, but they're actually being shot all wide open.
I don't follow. How can you have a manually set aperture but a body that ignores it? The body has no choice! Am I missing something again? Perhaps it's different lenses.

To clarify, my lenses are M42 Takumars. The aperture rings have no "A" position, but there is a switch for "manual" and "auto". I just have to be sure I'm in "manual" when I meter and shoot. Of course, "auto" leaves it stuck wide open.
02-20-2009, 05:41 PM   #7
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I'm not sure how M42 lenses work. I am sure somebody else here will chime in.

For reference though, (Sorry original poster, you probably realize this already) when using PK lenses, the body ignores the aperture ring.

This is because the lens is always wide open when it's on the body, and the camera has to close it down to take the picture.

(Although I have dabbed a lot in photography, I only just had that realization maybe 2 weeks ago)

Slightly mechanical explanation to follow.

If you look through a P-K lens when it's off the camera, you can twist the aperture ring (Provided it has one) and watch the blades close. On the back of the lens there is a little metal or plastic slider. It is spring-loaded. If you push against it, the lens opens up. So if you set the aperture ring to F/22 and then push on that lever, the lens opens wide up.

When you put the lens on the camera body, it pushes against that lever. This is so the lens is wide open so you can see to focus. Then when you take a picture the camera body moves a motor that releases pressure on that little lever, the lens diaphragm "stops down" to the value you selected with the aperture ring, and picture is taken.

You can also stop down the lens using the DOF preview...

With an "A" lens, the lens can tell the body what aperture setting you have selected. Therefore, the camera can meter wide open and then, using math, guess how much it needs to change the shutter speed to compensate for the reduced amount of light that will be coming into the lens when it's stopped down.

With "M" lenses, the camera doesn't know what aperture you've selected...so it can't make that adjustment.

You can try and stop-down meter in modes other than "M", but the lens does not actually stop down.

In fact in other modes you can activate the "DOF Preview" and you'll hear something in the camera body move (At least I do on K100D), but the lens does not actually stop down. Whatever is moving only couples to the lenses aperture-arm when in "M" mode.
02-20-2009, 05:49 PM   #8
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QuoteOriginally posted by eyou Quote
...
When I take the lens off of A mode using the aperture ring, and then press the AE-L button, nothing happens at all. Usually, when I press it not using the aperture ring, it will lock in that exposure (shows a * in the VF) to allow the camera to change aperture and shutter speed proportionally. I have tried just pressing the AE-L with and without half pressing the shutter button, but nothing happens at all. What am i doing wrong?
You indicate that the lens has an A mode. If that's the case you should just leave it on A. Exposure wise it then works like a DA lens and you can use all the exposure modes of the camera.

02-20-2009, 06:13 PM   #9
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QuoteOriginally posted by Ole Quote
You indicate that the lens has an A mode. If that's the case you should just leave it on A. Exposure wise it then works like a DA lens and you can use all the exposure modes of the camera.
I wanted to test it out so I could buy some fully manual lenses.

It was the +/- button!
02-21-2009, 10:20 AM   #10
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QuoteOriginally posted by wasser Quote
I don't follow. How can you have a manually set aperture but a body that ignores it? The body has no choice! Am I missing something again? Perhaps it's different lenses.

To clarify, my lenses are M42 Takumars.
Ah, that's different. I thought we were talking about K-mount lenses. With K-mont lenses, the aperture stays fully open as you turn the aperture ring (to make focusing easier). The camera moves a switch on the lens mount when it takes the picture in M mode in order to stop it down. The lens stops down to the selected aperture just long for the picture to be taken, then springs back open. The camera also stops down the lens when pressing the "meter" button or when doing a DOF preview.

In Av mdoe, however, the camera never moves the switch to stop down the lens. Not when you press the "meter" button, not when you do a DOF preview, and not when the picture is taken. So the lens remains fully open.

QuoteQuote:
The aperture rings have no "A" position, but there is a switch for "manual" and "auto". I just have to be sure I'm in "manual" when I meter and shoot. Of course, "auto" leaves it stuck wide open.
Right - and K-mount lenses are like the M42 lenses that are in "auto" all the time in that respect. Except that I'm not sure if any Pentax DSLR is capable of stopping down an M42 lens that is in "auto", but it definitely can for K-mount lenses if you are in M mode.

BTW, I keep mention DOF preview - that's something the K2000 doesn't have. On other Pentax DSLR's, it a switch you turn that causes the camera to stop down to the selected aperture for as long as you hold the switch. The original purpose was to let you check the DOF in the viewfinder. With manual K-mount lenses, though, it's also the only way to get a meter reading to display. When you use the "meter" button in M mode, it stops the lens down only momentarily, takes a meter reading, and sets a shutter speed to make the meter read 0.0, but then the lens opens up and the meter display turns off again.
02-21-2009, 03:54 PM   #11
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Saaby and Marc, thanks for taking the time to explain. I had not appreciated the differences in the bodies and the lenses. DOF preview and stop down metering didn't make much sense to me with my K2000. I think I get it now.
02-21-2009, 05:52 PM   #12
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Let me also say thanks to Saaby & Marc. I have 6 or 7 Taks and I have been getting hit or miss (mostly miss) shooting in M, so I have learned a lot from this thread. For example, I never knew about, or even thought about, what happens when the pressure is released from the slider and the lens opens wide open. Lots of good info in this thread.
02-22-2009, 02:05 AM   #13
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QuoteQuote:
Sabatella said:

In Av mdoe, however, the camera never moves the switch to stop down the lens. Not when you press the "meter" button, not when you do a DOF preview, and not when the picture is taken. So the lens remains fully open.
Not quite -- when you do the DOF preview (On K100D anyway) in Av mode, you will hear *something* moving, but whatever is moving does not actually engage the lens-stop-down lever.

I only mention it (or more appropriately, I'm only being such a stickler and mentioning it a second time now) because for awhile the noise misled me to believe the lens was stopping down, when in reality it was not.
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