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03-24-2011, 08:44 AM   #1

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Confirm my understand of metering w/ manual lenses focus hyperfocal focus

I am trying to select a manual lens for hyperfocal from-the-hip usage on my K-r. I'll be in and out of shade from buildings and do not want to press the green button before every photo. Basically, I want to set the focus and aperture once, then have the camera constantly adjust the shutter speed as needed.

(FYI 24mm appears to be my ideal length. It's the best compromise between field of view and DOF. The more commonly available 21mm and 28mm aren't as good for me.)

I've checked many posts and articles (such as the 2 below) and want to make sure I understand.
Shooting manual lenses on Pentax DSLRs

1) A Series and newer lenses work fine in Av mode. Manually set aperture using the e-dial (to around f11 for a deep DOF) and the camera will adjust shutter speed as needed. Correct?

2) M42 lenses can also be used in Av mode. Set the aperture on the lens (enable aperture ring in custom settings). The camera will show "F--" but should still continue to meter for shutter speed. The viewfinder will be dark but that's not a concern for hyperfocal usage. Correct?

3) M and K lenses need the green button and/or M mode. Av mode won't meter correctly. Correct?

4) I haven't found much about Adaptall-2. PKA adapters let Av mode work but seem to cost more than the lens. Can I get away with a cheap PK mount and use the aperture ring, or would that require a green button to reset shutter speed every time light conditions change?

03-24-2011, 09:04 AM   #2
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A-series should meter the same as more modern ones.

M42 lenses are supposed to work in Av, plenty of reports of the reality of that being less than rosy though. As you are going to stick to a more or less fixed aperture, exposure compensation should do it.

M/K will not stop down for exposure in Av.

The El-Cheapo adaptall adapter without the aperture lever would seem to result in the lenses to being equivalent to M42s. BTW ... I seem to recall seeing genuine adaptall-P/K adapters going for much cheaper on
03-24-2011, 03:42 PM   #3
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Your summary is pretty close

M42 lenses will work in Av mode but you may need exposure compensation depending upon lens, camera and aperture set. Once compensation is set you will be good to go

K& M lenses need green button to meter correctly in manual mode and do meter in Av mode but only wide open. Additionally these lenses may have metering errors again as a function of lens camera and aperture. Some cameras Do Not allow for ev comp in manual(k10 for certain)

A lenses work in either manual or Av mode and meter much better than M42 or K/M lenses
03-25-2011, 11:43 AM   #4
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On Av mode, my M42 lens meters very erratically--shutter speed bounces high and low seemingly randomly or it will need strong positive compensation one shot then negative compensation under the same light. I read that you need to use aluminum tape or sand off some paint at the base of M42 lenses to make sure they contact the pins on the body. Is this true or does this apply to another situation?

03-25-2011, 12:31 PM   #5
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Making the base conductive has been mentioned in connection with making "catch-in-focus" work with M42 lenses - I wouldn't be terribly surprised if metering was affected as well; it makes no sense as such to treat them differently but then nor does disabling CIF. Also, AWB results would seem to differ in tungsten light with the aperture ring of an A lens in / not in 'A' position (being mistaken for a M lens, probably) with no apparent rationale.

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