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03-22-2011, 01:41 PM   #1
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Manual apature stop-down metering?

Hello,

I've a Pentax K-x and I've just picked up a cheapy lens without an A setting for it. I have been searching around and have learned that 'stop-down' metering is what I need to look at for setting exposure but I'm having troubles with it.

Once fit the lens to the camera body it holds the aperture wide-open regardless of what it's set at. I have read that I need to set the green button mode to 'TV Shift' and when I press the green button it'll close the aperture to the manual setting and take a reading but pressing the button seems to do nothing (no swish sound of aperture closing).

Any ideas what I'm doing wrong?

03-22-2011, 01:47 PM   #2
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Have you configured your settings in the "custom setting menu" to allow use of aperture ring? (Page 283-284 of the manual)
03-22-2011, 01:50 PM   #3
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I have set the 'using aperture ring' setting to '2 permitted'
03-22-2011, 01:51 PM   #4
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The first thing that you need to do is to go into the Custom Function settings and "enable" use of a lens when the aperature is set to other than A. This will allow lenses to be used when they are not set to A or do not have an A setting.

Then set the camera in manual mode and for the K-X press the green button, I think. This will stop down the lens and allow a meter reading and corresponding shutter speed to be obtained for the set aperature. When the shutter button is fully depressed, the camera will stop the lens down to the selected aperature and use the metered shutter speed to take a photo.

Regards

Chris Stone

03-22-2011, 01:54 PM   #5
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When I press the shutter button it stops down the aperture to take the photo, but I can't seem to make the green button stop it down to take the meter reading.

I've tried the optical preview function on the green button too and that doesn't work (although definitely does with the kit lens)
03-22-2011, 01:54 PM   #6
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The mode dial has to be set at M (manual) and "Using Aperture Ring" has to be set to "permitted" (item 22 in the custom menu pg 4)
If you are still having problems check out this link

NaCl(let us know how you make out)H2O
03-22-2011, 02:02 PM   #7
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What lens?

1) On the K-x, you don't have to use the Green button for this and assign it as Tv Shift. The Ev+- button does the same thing, so you can assign the Green button to do something else. (I shoot JPEGs 99% of the time, so mine is set to toggle to RAW mode.)

2) You have to set your camera to "Use Aperture Ring--PERMITTED." You can leave it like that forever, because this won't affect operation of your modern auto lenses.

3) When you're set up like thiis, you manually turn your aperture ring first...hit the Ev button...and the camera sets the shutter speed. It's kind of like Av mode, but you have to hit the Ev button each time if light conditions change.

4) And that's the reason you don't hear any noise. The cam can't automatically change the aperture--the older lens is incapable of this. It can only change the shutter speed.

Last edited by Ira; 03-22-2011 at 02:10 PM.
03-22-2011, 02:02 PM   #8
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QuoteOriginally posted by Chonker Quote
When I press the shutter button it stops down the aperture to take the photo, but I can't seem to make the green button stop it down to take the meter reading.

I've tried the optical preview function on the green button too and that doesn't work (although definitely does with the kit lens)
It takes the meter reading as it stops down the aperture. These electronic gizmos are quick!!!
Try this: find something fairly bright to take a shot of. Make sure the mode dial is in M. Set the lens to a fairly middle aperture. Check the shutter speed in the VF. Hit the green button (you should hear a mechanical noise as the mirror flips up, the aperture is stopped down and the reading is taken) and check the shutter speed again, it should be slower

NaCl(but you have to be in M mode)H2O


Last edited by NaClH2O; 03-22-2011 at 02:10 PM. Reason: changed "wide open" to middle and "faster" to slower
03-22-2011, 02:05 PM   #9
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QuoteOriginally posted by Ira Quote
What lens?

1) On the K-x, you don't have to use the Green button for this and assign it as Tv Shift. The Ev+- button does the same thing, so you can assign the Green button to do something else. (I shoot JPEGs 99% of the time, so mine is set to toggle to RAW mode.)

2) You have to set your camera to "Use Aperture Ring--PERMITTED." You can leave it like that forever, because this won't affect operation of your modern auto lenses.

3) When you're set up line this, you manually turn your aperture ring first...hit the Ev button...and the camera sets the shutter speed. It's kind of like Av mode, but you have to hit the Ev button each time if light conditions change.

4) And that's the reason you don't hear any noise. The cam can't automatically change the aperture--the older lens is incapable of this. It can only change the shutter speed.
Actually Ira there is a slight mechanical noise as the mirror is flipped up and the aperture is stopped down to the preset opening.

NaCl(even my ancient and elderly ears can hear it)H2O
03-22-2011, 02:10 PM   #10
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QuoteOriginally posted by Chonker Quote
Hello,

I've a Pentax K-x
QuoteOriginally posted by Chonker Quote
When I press the shutter button
QuoteOriginally posted by Ira Quote

1) On the K-x, you don't have to use the Green button for this and assign it as Tv Shift. The Ev+- button does the same thing, so you can assign the Green button to do something else. (I shoot JPEGs 99% of the time, so mine is set to toggle to RAW mode.)

2) You have to set your camera to "Use Aperture Ring--PERMITTED." You can leave it like that forever, because this won't affect operation of your modern auto lenses.

3) When you're set up like this, you manually turn your aperture ring first...hit the Ev button...and the camera sets the shutter speed. It's kind of like Av mode, but you have to hit the Ev button each time if light conditions change.

4) And that's the reason you don't hear any noise. The cam can't automatically change the aperture--the older lens is incapable of this. It can only change the shutter speed.

For some others reading along, it is worth noting that the "stop down" metering with the K-x and K-7 anyway, the actuation is very, very quiet; unlike the previous models such as the K10 and K20.
03-22-2011, 02:13 PM   #11
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I swapped to a different lens, one which has an A setting but also manual selections and set an aperture on the ring and the green button started working, making a swishing noise, viewfinder going dim and shutterspeed changing. So I guess it's a problem with this lens, but it's weird because it manages to stop down okay when the shutter is pressed
03-22-2011, 02:13 PM   #12
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QuoteOriginally posted by Nowhere Matt Quote
For some others reading along, it is worth noting that the "stop down" metering with the K-x and K-7 anyway, the actuation is very, very quiet; unlike the previous models such as the K10 and K20.
It is quiet but you can hear it. At least I can and I have 62 year old ears.

NaCl(and I was in a lot of rock and jazz bands when I was much younger)H2O
03-22-2011, 02:16 PM   #13
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QuoteOriginally posted by NaClH2O Quote
Actually Ira there is a slight mechanical noise as the mirror is flipped up and the aperture is stopped down to the preset opening.

NaCl(even my ancient and elderly ears can hear it)H2O
No noise on mine with Ev. I'm also curious whether this a K lens that will only shoot wide open.

The main thing is, with anything before Pentax M lenses, the camera is incapable of changing the aperture of the lens because the lens can't do it. There is nothing "electrically connected" to change the manually set (by hand) aperture of, let's say, a Super Takumar.
All the cam can do is change ISO and shutter speed for correct metering.
03-22-2011, 02:20 PM   #14
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Chonker,
On the back of the lens in question there is a small rectangular metal tab. Set the lens to something like f/8 and push the tab sideways, the tab should move and you should see the aperture blades contract down to a much smaller opening. If that doesn't happen you have a bum lens. If it does stop down, then try mounting the lens to your camera and try taking a picture of a bright scene. Set the aperture to somewhwere in the middle and see if the pic comes out properly exposed and check the info on the lcd screen on the back of the camera.

NaCl(maybe you have a sticky lens)H2O
03-22-2011, 02:23 PM   #15
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Are you guys telling me that the mirror has to flip up for metering on the K-x?
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