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03-30-2010, 01:34 PM   #1
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Pentax-, lens metering.

ok, sooooo

i put on the gemini 80-200 f4.5
i check custom settings apature ring allowed, check.
i set it to manual mode. check.

i get no meter......

siiiigh.

i use the green button, it sets my shutter speed.

i snap a picture, its too bright... i had no meter.

what gives?

PS the title should say pentax-m lense metering.
pps k20d


Last edited by ravenxbishop; 03-30-2010 at 01:59 PM.
03-30-2010, 01:41 PM   #2
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Which camera?
03-30-2010, 01:41 PM   #3
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I don't know what camera you are using but there are some exposure errors with the K10D, K20D, to a lesser extent the K7D and manual aperture lenses

Also metering is only done using manual mode and pressing green button, at which point, as you discover it sets the shutter speed.

conversely if you have the ability to check DOF the meter is active with optical DOF preview.

You can also shoot in Av mode, just that all shots are wide open. the lens will not stop down in AV mode

this is how the cameras work.
03-30-2010, 02:10 PM   #4
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its a k20d put that in pps.

so, theres a way to get the meter working when the green button is pressed???

03-30-2010, 02:11 PM   #5
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If you shoot mainly wide open (or near it), you'd be better with a little tweaking of your lens to transform it into a preset lens.

Just drill another locking hole into the lens, so it locks halfway into the mount. The aperture ring will have a direct effect onto the aperture, and you'll be able to use Av mode at all apertures.

Better still, you can still lock it with the original hole, so it's still fully functionnal as a PK-m lens.
03-30-2010, 02:13 PM   #6
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Be sure to thoroughly read the sticky thread at the top of the beginner's forum on using manual lenses. But since the camera took a picture at all, then obviously you managed to find the "use aperture ring" setting, and it looks like you found the green button, too, so you're probably not doing anything wrong. But if you want to actually see a meter reading, the DOF preview will do that for you, as explained in that thread (I think).

One thing to be aware of is that with manual lenses, matrix metering is not available, so you get center-weighted instea,d which can in some cases create significantly brighter images than you are accustomed to (no ability to protect highlights). Another is that on some camera models, metering gets increasingly less accurate as you stop down, because the metering system wasn't really designed to be used stopped down. It's also possible the aperture blades on your lens are slow and not closing in time.

If none of that explains what you are seeing, then you might try posting an image.
03-30-2010, 02:33 PM   #7
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QuoteOriginally posted by ravenxbishop Quote
its a k20d put that in pps.

so, theres a way to get the meter working when the green button is pressed???
No

Metering works when you activate the DOF preview (optical preview) by extending the on off switch past ON, this stops down the lens and activates the metering.

the green button can only set shutter speed to match aperture.

Also, note the performance of the metering (i.e. setting of shutter speed) as a function of aperture, On the cameras I own

The K20 is similar to the K10 as they both share the same focusing screen, which seems to be the cause of the exposure error issue, If you are around F8 to F16 then you may be over exposing by 1.5 to 2 stops

03-31-2010, 09:39 AM   #8
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thanks

you know that was all very very helpful.

the manual isnt really clear about this process.

so, based on your leads... i did optical live preview DOF.
which puts the metering in the mirror. and it seems that in most if not all cases for THAT lens i need to use the meter as if the target was 2 bars above center (really more like 1.5 bars.)

with this part working im so in love with this camera its absolutely retarded.

now if i could only find a reasonably priced pentax-a f/1.2 50mm

i think i'll be set until 20mp

not that pentax would listen to ME but it seems to me, they could easily, let you set the f-stop 1.0 to 22 or so... and show you the metering... just requiring you to set the ring to the same stop as you set the camera.

it would at the very least be a solution for speed.

this work around isnt bad at all... and im gleeful playing with my lenses now.

anyone know a better sorce for old lenses than ebay? the only 1.2f i see is $500
i'm waay under that.

03-31-2010, 12:28 PM   #9
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keh.com is my go to source - not necessarily cheaper than ebay, but more straightforward and reliable. that and the marketplace forums right on this site.
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