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03-02-2015, 06:29 AM   #1
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Tamron lens question

Another question from me! Apologies if this has already been asked, I looked but couldn't see anything specific.

I currently have two Tamron adaptall 2 manual focus lenses, the 28-70mm and the 70-210mm. There is a tamron Pentax KA mount which I swap betweeen the two lenses as required. Works fine on my old Super A and P50.

My K50 seems to recognise the lenses, at least partially, as it asks me for a focal length, so I input whichever length I want to use, say 200mm for instance.
Should I input the 35mm focal length, or multiply by 1.5 to give the approx focal length on the K50? i.e 50mm film lens, input focal length as 75mm?

Also when the lenses have the aperture set to "A" it doesn't give me the aperture in the viewfinder, but on the rear screen it does. (On my Pentax A 50mm f1.7 lens it shows the f value in both viewfinder and rear screen.)
Also in MF mode on the camera, I dont get focus confirmation dot in hte viewfinder or beep like I would with the 50mm A lens.

Are these just down to the fact they are non-genuine lenses, so have a more limited compatibility or do I have to edit some settings on the camera, or just use them manually?

Many thanks

03-02-2015, 06:52 AM   #2
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KISS...put in the actual focal length.
03-02-2015, 07:01 AM   #3
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Ok, that clarifies that side, thanks.

Any thoughts about the F stop display side of things?
03-02-2015, 07:43 AM   #4
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I can't grasp how the f stop can appear only on the rear lcdand not the viewfinder. That's odd. To clarify, are you seeing it show up correctly when you shoot with optical viewfinder and then review the shot (ie it made it into exif) or are you saying that it shows in live view while you shoot?

03-02-2015, 08:05 AM   #5
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If it shows it live mode but not the viewfinder it is usually showing the wrong aperture in live mode -- that's a glitch, it is not reading the lens correctly. (Does it say things like f/1.2 on the screen?) I've seen that before...
03-02-2015, 08:12 AM   #6
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The f stop info only shows in the rear screen, not in the viewfinder.
This is before I've taken the shot. Normally the info is duplicated in both. Having read the manual for the K50 it does do that on some lenses.
I suspect it is the interchangeable mount, as the camera is fine with Pentax A and DAL lenses.
The mount dates back to the early 90s (as do the lenses). So they pre-date most AF stuff.
03-02-2015, 08:42 AM - 1 Like   #7
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I have had this sort of thing with my adaptall lenses and adapters. Often it is fixed by giving the lens a "wiggle", or switching on and off.
Test that the lens + adapter is operating correctly in any case by taking some test shots.

As far as focus confirm goes, for that check you camera settings. That should not be affected by or dependent on whether the PKA is playing up or not (which you can confirm by taking it out of auto aperture mode and using Manual).

There are some more useful links on my page:
Information page on Tamron adaptall, adaptall-2 system and lenses

UPDATE: and I'd forgotten about this:
https://www.pentaxforums.com/forums/114-maintenance-repair-articles/50689-fix...a-adapter.html

I was just fiddling with two PKA's acquired with lenses that weren't registering. 10 secs scratching with a small screwdriver - fixed!

Last edited by marcusBMG; 03-02-2015 at 09:06 AM.
03-02-2015, 09:40 AM   #8
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QuoteOriginally posted by marcusBMG Quote
I have had this sort of thing with my adaptall lenses and adapters. Often it is fixed by giving the lens a "wiggle", or switching on and off.
Test that the lens + adapter is operating correctly in any case by taking some test shots.

As far as focus confirm goes, for that check you camera settings. That should not be affected by or dependent on whether the PKA is playing up or not (which you can confirm by taking it out of auto aperture mode and using Manual).

There are some more useful links on my page:
Information page on Tamron adaptall, adaptall-2 system and lenses

UPDATE: and I'd forgotten about this:
https://www.pentaxforums.com/forums/114-maintenance-repair-articles/50689-fix...a-adapter.html

I was just fiddling with two PKA's acquired with lenses that weren't registering. 10 secs scratching with a small screwdriver - fixed!
Wonderful! Thanks Marcus, I'll take a look at the mount tonight. More fiddling!
fingers crossed thats all it needs doing.

03-02-2015, 02:12 PM   #9
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Well a full disassembly of the Tamron P-KA mount has yielded some improvements. I cleaned all the elctrical contacts and filed the tips of the 3 screws that act as contacts between the camera body and the lens to ensure a clean contact. <br />
I now get the in focus light and confirmation beep which I didnt before. It still doesn't show the f number in the viwefinder, but it does on the display. but I think thats more to do with the camera not really knowing what lens its dealing with. Im not too worried about it as they're old lenses.

Last edited by bigyinn; 03-02-2015 at 02:54 PM.
03-02-2015, 02:17 PM   #10
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QuoteOriginally posted by bigyinn Quote
Well a full disassembly of the Tamron P-KA mount has yielded some improvements. I cleaned all the elctrical contacts and filed the tips of the 3 screws that act as contacts between the camera body and the lens to ensure a clean contact.
I know get the in focus light and confirmation beep which I didnt before. It still doesn't show the f number in the viwefinder, but it does on the display. but I think thats more to do with the camera not really knowing what lens its dealing with. Im not too worried about it as they're old lenses.
A properly working PKA mount will show the aperture in the viewfinder just fine.
03-02-2015, 03:25 PM   #11
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You're probably right!

If anyone has a working P-KA mount, please let me know if they want to sell it!
03-03-2015, 01:41 PM   #12
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Success!
Having fiddled about the lens again and holding the lens locking pin down whilst rotating the lens past the normal locking point, I could get the f numbers to appear in the viewfinder.
So I carefully filed about 0.5mm extra from the locking pin engagement slot in the lens mount, thus permitting the lens to rotate slightly further before engaging.
So I now have focus confirmation and the correct f values displayed in the viewfinder.
Job done!
Thanks to everyone for their help and suggestions.
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