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07-11-2016, 06:46 AM - 1 Like   #1
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Tokina 28mm 2.8

I have an old Tokina 28mm f2.8 lens that I bought back in the 80's. Didn't have much money so I probably went for cheap. This is not an RMC as some are. I'm not sure what the RMC stands for but if I had to guess I'd say it has to do with the coating. My primary question is this. On the aperture ring next to f22 there is an A (colored green) and I was wondering what that A represents. There is a small button on the aperture ring that, when depressed, will allow you to rotate the ring to the A position and it will remain locked on the A once you've rotated it to line up with the dot. I don't believe I've shot this lens in more years than I can remember but I'm going to give it a test run on some black and white film soon. I hope its not too big a wast of a few frames of film.

Thanks in advance to anyone who might choose to make worthwhile comments on this subject.

Regards


(Long live film)

07-11-2016, 07:56 AM   #2
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The 'A' position allows the camera (if it can) to control the aperture. So on any DSLR this would be the preferred setting to allow the camera wheel to control aperture and also to allow it to be recorded in EXIF. On a film camera it would depend on the camera as to whether the camera had that capability. I'm not familiar with film models so I cannot help there, but since you bought it back then I might guess it would work with your camera.
07-11-2016, 08:01 AM   #3
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I have had a Tokina 28mm 2.8......it preforms Just fine on Film and Digital....... No waste of film for sure.
07-11-2016, 08:57 AM   #4
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https://en.wikipedia.org/wiki/Pentax_K-mount#KA-mount

MF lenses without the "A" setting on the f-stop ring limit you to using manual mode with the green button to meter and adjust the exposure on DSLR. With the "A" setting you can use Av (aperture priority) and other automatic modes like P (program).
Early film cameras with the K mount like the K1000, ME, ME super, MX, LX... don't make use of the "A" setting, but were typically designed for aperture priority (you spin the aperture dial to your F stop, camera auto adjusts the shutter speed). I think the first KA mount camera was the Super A?

07-11-2016, 10:07 AM   #5
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QuoteOriginally posted by FishrOfGrizz Quote
On the aperture ring next to f22 there is an A (colored green)
As noted above, "A" on a K-mount lens means that the lens has electrical contacts on the base to support aperture control by the body. The is a good thing because it means that the lens supports all all exposure modes on modern Pentax dSLRs as well as all Pentax-brand K-mount film bodies. There is one small caution, however, that pertains to third-party makers such as Tokina. It was not unusual to include not only Pentax mount contacts, but also a small pin to support Ricoh's program exposure cameras. The so-called "Ricoh Pin" is located at the same position on the mount as the AF drive cog on Pentax auto-focus bodies and creates potential that the lens may become stuck on the camera due to interference with the AF cog "well". That is why it is often referred to as "The Dreaded Ricoh Pin".

There are two varieties of the Ricoh Pin. The more dangerous is a square cut round pin. Less hazardous is a round-topped version. Several users on this site (myself included) have successfully used lenses with the round-topped pin. Both types should be considered with caution. Clues to whether the pin might be present are:
  • Ricoh/Rikenon "P" lenses with green "P" on the aperture ring
  • Third-party K-mount lens with "A" and/or "P" position on aperture ring
  • Markings on base or barrel: K/R, PK/R, R/K, KA/R, etc.
  • Goggle "Ricoh Pin" for diagrams showing location of the pin
It is possible to surgically remove the pin on offending lenses rendering them harmless.


Steve
07-14-2016, 10:42 AM   #6
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It took you 30 some years to ask this question. What a brave person you are.
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