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04-23-2010, 11:39 AM   #1
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overexposure with tamron pka adpater and...

overexposure (BIG TIME) with newly acquired tamron adaptall 70-210mm f3.5 and pka adapter....
lba strikes again.... i've never had any problems with overexposure with any lens i employ, whether it be manual or an af lens... on either my old k200d or newer k-x....
i slapped the pka adapter on the tammy lens, clicked neatly in place, mounted it to the k-x... and it does recognize the f3.5 on the rear lcd and also asks me to enter what focal length i want for sr... (i have allowed to camera body to use manual focus lenses)....
i took the lens out for a trial, both in my home and in my yard... and whoa!! tremendous overexposure.... and even when dialing in big time negative exp compensation.... still not right...
all i can find online is some anecdotal stuff about users having some overexposure issues.... but i thought i'd pick the brain of my forum friends.......
i'm thinking that the adapter is the culprit.... but do i need to scrape those electrical contacts of file them with one of my wife's emery boards?? or is there something else about this adapter which may be causing this BIG problem?????
thanks in advance for your help and insight...
(i did pm hin, the techman... seems to be an adaptall guru)
dave meyers

04-23-2010, 12:05 PM   #2
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Doesn't make any sense. Something has to be set wrong.

See what pattern your metering is set to.

You shouldn't be getting over in the first place.
04-23-2010, 12:20 PM   #3
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are you sure your aperture is moving

what if you set it to F3.5 what exposure do you get?

it may be that the lens is not stopping down at all or you raperture blads are sticky

if you manualll activate the aperture does it stop down the lens
04-23-2010, 01:29 PM   #4
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Remove the mount. Wipe it good with a micro fiber cloth. Put it back on. Make sure it is at the 32 position and try it in Av mode with your body. Taking the mount of also serves to "re-seat" the mount and not just cleaning it.

04-23-2010, 01:34 PM   #5
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THere are two tabs in the mount that must fit into slots on the lens (or the other way around), one sets the max aperture and the other registers current aperture. The main tricky bit in seating a KA adaptall is to get these two tabs to mate properly. Once they do, you should not have any problems.

There's a release button for the A setting on the aperture ring in the mount, if that's not properly set perhaps you can be slightly out of A mode?

You may want to clean the electric contact points as well.

04-23-2010, 01:51 PM   #6
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My solution does cost some money if you don't have another Adaptall lens but it would sort out which part the culprit is.

Buy an Adaptall lens, any Adaptall 2 lens will do. Try it on the PK/A adapter and if the problem persists it must be the adapter. Otherwise something is wrong with your 19AH Lens. Another Adaptall lens should not be too expensive, enough 80-210 lenses that can be bought for next to nothing. Doesn't matter if it is the 03a or 103a version, only if you want to keep the lens go for the 103a.
04-23-2010, 02:13 PM   #7
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QuoteOriginally posted by EricR Quote
My solution does cost some money if you don't have another Adaptall lens but it would sort out which part the culprit is.

Buy an Adaptall lens, any Adaptall 2 lens will do. Try it on the PK/A adapter and if the problem persists it must be the adapter. Otherwise something is wrong with your 19AH Lens. Another Adaptall lens should not be too expensive, enough 80-210 lenses that can be bought for next to nothing. Doesn't matter if it is the 03a or 103a version, only if you want to keep the lens go for the 103a.
thanks eric... i guess great minds think alike ... besides trying the very good suggestions listed above... i bought another adaptall lens... from pacific rim camera, for 35 bucks delivered... in excellent condition.... i'll give that one a go... then see what's the issue, the adapter or the lens.....
regards, dave m... the lba man...............
04-23-2010, 02:24 PM   #8
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Keep us updated. Would suprise me if it's the 19AH because it's build like a tank. But now you can sort out the problem and maybe can fix the adapter or the lens.

The 19AH is a great lens, doesn't come any smoother for focussing and zooming if the lens is in a good condition. And no lens creep too, quite nice for a lens of this weight and size.

04-23-2010, 06:32 PM   #9
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QuoteOriginally posted by dcmsox2004 Quote
overexposure (BIG TIME) with newly acquired tamron adaptall 70-210mm f3.5 and pka adapter....
lba strikes again.... i've never had any problems with overexposure with any lens i employ, whether it be manual or an af lens... on either my old k200d or newer k-x....
i slapped the pka adapter on the tammy lens, clicked neatly in place, mounted it to the k-x... and it does recognize the f3.5 on the rear lcd and also asks me to enter what focal length i want for sr... (i have allowed to camera body to use manual focus lenses)....
i took the lens out for a trial, both in my home and in my yard... and whoa!! tremendous overexposure.... and even when dialing in big time negative exp compensation.... still not right...
all i can find online is some anecdotal stuff about users having some overexposure issues.... but i thought i'd pick the brain of my forum friends.......
i'm thinking that the adapter is the culprit.... but do i need to scrape those electrical contacts of file them with one of my wife's emery boards?? or is there something else about this adapter which may be causing this BIG problem?????
thanks in advance for your help and insight...
(i did pm hin, the techman... seems to be an adaptall guru)
dave meyers
Sorry that I missed your post and I probably missed your email. I have been busy lately.

It is NOT normal to get over-exposures as I have not run into one in all of my tamron adaptall-2 lens. And I do have multiple copies of pk-a adapter. I think you need to re-read Nester post and look over the instruction on the adaptall-2 adapter. There are two tabs and you need to line them up correctly. If properly mounted, you should see the aperture settings in the LCD as in F5.6 in Av mode and you should be able to adjust the aperture in the rear dial. Strangely on the K-x, I see F-- in the viewfinder while the LCD is always showing the correct F aperture settings.

Check if your LCD shows F-- as that will indicate mounting problems. If overexposure persist in Av mode, I will suggest trying out in M mode with stop-down and see what goes from there.

The Tamron SP 70-210mm f/3.5 (19AH) is probably one of the best manual focus zooms that I have used in that zoom range. I much prefer it over the Vivitar Series 1 zoom. Occasional finding with PF is common but the sharpness from that zoom as well as the focusing ring will sure make you happy.

Thanks,
Hin

Last edited by hinman; 04-23-2010 at 06:51 PM.
04-23-2010, 06:45 PM   #10
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Recent shots on Pentax K-x and Tarmon SP 70-210mm f/3.5 (19AH) on wildflowers












04-23-2010, 06:46 PM   #11
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FWIW (since others have made all the suggestions I could think of) I have 2 Adaptall-2 lenses and 2 SP lenses, including the #19AH, and I have no metering/exposure problems with any of them. In fact three produce some of the prettiest images I have ever taken.

There is an article here about LIGHTLY scraping the third contact to remove the blue coating but that is to permit proper aperture controls through the camera body.

One (probably stupid) question, since you use manual lenses - did you use the Green Button to meter before you released the shutter?
04-23-2010, 07:03 PM   #12
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Hi dcmsox,

I have quite a few PK/A adapters, and a couple have needed to be modified a bit to get them to stop lenses down properly, but it was always a matter of underexposure with mine. The cause was the lever that linked to the Pentax aperture actuator -- it wouldn't allow the aperture blades to open up fully, and it had to be bent up to correct this, so I doubt that would be the problem. The "scraping the contacts" thing is a fix for the aperture not registering with the camera, so that's not the problem.

That being said, I would think that sticky aperture blades, a bent actuator lever that causes extra friction, or a weak aperture blade return spring would be the most likely suspects (as they would be in any "regular" K mount lens). I've had all three happen in used lenses, and the bent actuator lever happened on an "open box" Sigma Ex 180 Macro that apparently was returned to the dealer -- nice to get a $350 discount for a problem that took a few seconds to cure. Have you checked these?

Scott
04-24-2010, 06:20 AM   #13
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thanks all for your input.... i ran some alcohol around the contacts... re-read the mounting instructions... re-mounted the pka adapter.... working almost perfectly... with the exception of only reading f4... not f3.5.... close enough for government work as they say????
i'm getting much better/accurate exposure than my feeble first attmepts...
i've never been known as a patient man... and like many of the male species.... think instruction manuals are for other folks..... i've have lived and i have learned...
regards, dave m.... here in sunny rhode island... at least for now....
04-24-2010, 08:42 AM   #14
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Good to hear you got it sorted out. It's not the easiest adapter to install.
04-24-2010, 09:19 AM   #15
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thought this was excellent... for our adaptall pentax shooters..
Features and Operation of the Ka Mount
noting the following excerpt.........
The Tamron KA Adaptall Mount

When Joachim Hein read the above discussion, he immediately understood the roots of the exposure problems that some Adaptall lenses have. These are all "slow" lenses with minimum aperture setting of f/22 and an "AE" setting or f/32 and no "AE" setting In the latter case, f/32 is converted to "AE"). "AE" is the Tamron equivalent of the Pentax "A" setting. Looking in the second column of the table above, we see that there is no contact pattern for lenses with apertures ranging between f/4.5 or slower and f/22. Tamron solves this by making the Adaptall mount indicate a maximum aperture of f/4 and warning in the mount manual that the photographer must watch the aperture read-out in the view-finder (not available with P30/P50!) to ensure that only values within the true aperture range are used.
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