Tokina RMC 80-200mm F4 PK/A mount - infinity focus adjustment for long end

mlipovac · 12-07-2015, 01:29 AM

Hi there,
just two weeks ago I've purchased used lens as from title, from ebay seller. Price was 34€ + 7€ shipping

First test showed very pleasing results regarding IQ, color and sharpness. But, soon I've discovered that on 200mm position maximum object distance to be focused is approx 10m when focus ring hits the infinity stop. No infinity focus.
After first shock, visited every forum that can give me more information about infinity focus adjustment, but no luck with this Tokina version. Search took almost two weeks, when I finally found one post on chinese DIY forum where exactly my type of Tokina is disassembled for glass cleaning. After a while, I've managed to disassemble the front tube off the lens and get access to front lens focusing group. Then I figured out that only contact zoom ring has with front lens group (wich sits on a focusing helicoid) is via front tube that holds the nameplate ring. Three tiny flat screws around tube are giving friction contact between that tube and focusing helicoid (see pictures).
So, to adjust lenses for infinity focus, set zoom ring on infinity position and just loosen those three screws (just loosen, a one turn is enough, if you unscrew it, they are so tiny that it will be prety hard to get them back in place) to discard tube contact with focusing helicoid. When screws are loose, return zoom ring to a bit closer than infinity mark (notice that you won't move focusing helicoid now because there's no contact with tube), and then fasten just one screw, attach lenses to a camera and try to get distant object into focus by turning focusing ring. If focus is still not achieved, repeat the process (loosen the screw and return focus ring further from infinity, tighten it again and test) as many times it takes to get real infinity.
Once you have infinity focus, loosen the screw again, try not to move helicoid by any other mean when turning zoom ring to a infinity mark. Then tighten all three screws back - you have done infinity focus adjustment.

For the same thing on a zoom short end (80mm) I didn't have to align anything, so I can't tell how it could be done.

Hope this will help to someone like me...

Attached Images

**marcusBMG** · 12-07-2015, 08:22 AM

I have the same lens in MD mount, acquired it ages ago with other lens(es). I had a similar problem front end fell off! Your description that the grub screws are the key is right on.
PKA mount version of this lens is rare. Tokina soon replaced the rmc lenses with the later SD f4-5.6 compact zoom tp's.

mlipovac · 12-08-2015, 12:23 AM

Yes Marcus, I'm very happy with A setting with this lens, leaves only focusing and zooming to manual control. When you say it's rare to find PK/A mount version, it makes me even more happy :-)
Second image shows donut ring fastened with screw to a front tube - this is the contact with zoom ring, just for getting a picture how it works and it's not needed to touch this when adjusting infinity focus.

lothalev · 04-25-2016, 12:36 AM

Hello from Poland. Thanks to your tutorial, I have adjusted infinity focus on a freshly acquired Tokina 80-200 f/4 (FD mount). What bothers me more is that everything on the photo is distorted (looks like either out-of focus or massive chromatic abberation). I've used it on Samsung NX1000 with NX-FD adapter from Kecay.
Do you have any idea what could be wrong?

The car sample is a scaled down middle of the photo crop, where I focused. Note that although it is focused, nothing is sharp.
The bird photo is the best I got with that lens. The scaled down photo looks quite promising, but 100% sample crop reveals that again - nothing is sharp despite being in focus. The bird photo was shot with f/11.
Is the lens broken? Or needs some additional adjustment?

Thanks for any hints

Attached Images

View Picture EXIF

View Picture EXIF

ScooterMaxi Jim · 04-25-2016, 08:32 AM

As for the shots above, the lens has to be severely out of alignment and/or elements are loose. Having sold many of those lenses new back in the day, it always performed very well in terms of sharpness despite average coatings and somewhat middling contrast.

When I was selling the lens, we never got the PK/A version - and didn't know it ever existed. With the advent of the PK/A mount, we transitioned to the much smaller 4-5.6 variable aperture version that was quite popular, but not as strong optically or in build.

lothalev · 05-04-2016, 11:12 PM

The lens was indeed DOA. I've acquired another 80-200 lens on an auction, again, ~$10 + shipping.
This time Polar f/3.9 80-200 MC with Canon FD mount. This one is a keeper. No issues with either infinity focus or image clarity/sharpness. Worked straight after connecting to a FD->Samsung NX adapter.

So I guess for cheap lenses, it makes more sense to buy another one than try to fix the one you have

12-07-2015, 01:29 AM	#1
mlipovac New Member Join Date: Dec 2015 Posts: 7	Tokina RMC 80-200mm F4 PK/A mount - infinity focus adjustment for long end Hi there, just two weeks ago I've purchased used lens as from title, from ebay seller. Price was 34€ + 7€ shipping First test showed very pleasing results regarding IQ, color and sharpness. But, soon I've discovered that on 200mm position maximum object distance to be focused is approx 10m when focus ring hits the infinity stop. No infinity focus. After first shock, visited every forum that can give me more information about infinity focus adjustment, but no luck with this Tokina version. Search took almost two weeks, when I finally found one post on chinese DIY forum where exactly my type of Tokina is disassembled for glass cleaning. After a while, I've managed to disassemble the front tube off the lens and get access to front lens focusing group. Then I figured out that only contact zoom ring has with front lens group (wich sits on a focusing helicoid) is via front tube that holds the nameplate ring. Three tiny flat screws around tube are giving friction contact between that tube and focusing helicoid (see pictures). So, to adjust lenses for infinity focus, set zoom ring on infinity position and just loosen those three screws (just loosen, a one turn is enough, if you unscrew it, they are so tiny that it will be prety hard to get them back in place) to discard tube contact with focusing helicoid. When screws are loose, return zoom ring to a bit closer than infinity mark (notice that you won't move focusing helicoid now because there's no contact with tube), and then fasten just one screw, attach lenses to a camera and try to get distant object into focus by turning focusing ring. If focus is still not achieved, repeat the process (loosen the screw and return focus ring further from infinity, tighten it again and test) as many times it takes to get real infinity. Once you have infinity focus, loosen the screw again, try not to move helicoid by any other mean when turning zoom ring to a infinity mark. Then tighten all three screws back - you have done infinity focus adjustment. For the same thing on a zoom short end (80mm) I didn't have to align anything, so I can't tell how it could be done. Hope this will help to someone like me... Attached Images

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12-07-2015, 08:22 AM	#2
marcusBMG Site Supporter Join Date: Nov 2012 Location: North Wales Photos: Gallery \| Albums Posts: 2,869	I have the same lens in MD mount, acquired it ages ago with other lens(es). I had a similar problem front end fell off! Your description that the grub screws are the key is right on. PKA mount version of this lens is rare. Tokina soon replaced the rmc lenses with the later SD f4-5.6 compact zoom tp's.

12-08-2015, 12:23 AM	#3
mlipovac New Member Join Date: Dec 2015 Posts: 7 Original Poster	Yes Marcus, I'm very happy with A setting with this lens, leaves only focusing and zooming to manual control. When you say it's rare to find PK/A mount version, it makes me even more happy :-) Second image shows donut ring fastened with screw to a front tube - this is the contact with zoom ring, just for getting a picture how it works and it's not needed to touch this when adjusting infinity focus.

04-25-2016, 08:32 AM	#5
ScooterMaxi Jim Veteran Member Join Date: Jul 2009 Location: Minnesota Posts: 1,520	As for the shots above, the lens has to be severely out of alignment and/or elements are loose. Having sold many of those lenses new back in the day, it always performed very well in terms of sharpness despite average coatings and somewhat middling contrast. When I was selling the lens, we never got the PK/A version - and didn't know it ever existed. With the advent of the PK/A mount, we transitioned to the much smaller 4-5.6 variable aperture version that was quite popular, but not as strong optically or in build.

05-04-2016, 11:12 PM	#6
lothalev New Member Join Date: Apr 2016 Posts: 2	The lens was indeed DOA. I've acquired another 80-200 lens on an auction, again, ~$10 + shipping. This time Polar f/3.9 80-200 MC with Canon FD mount. This one is a keeper. No issues with either infinity focus or image clarity/sharpness. Worked straight after connecting to a FD->Samsung NX adapter. So I guess for cheap lenses, it makes more sense to buy another one than try to fix the one you have