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Tokina 800mm F8 adapter question
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PostPosted: Sun Aug 08, 2021 10:40 pm    Post subject: Reply with quote
I can clearly see the issue. Both our lenses are at infinity focus, but my copy just can not get as close as yours. I am having trouble removing the screws on the grip and do not want to damage them. Do you think the issue is with the focus assembly?
I can take more pics of the inside if needed?


PostPosted: Mon Aug 09, 2021 1:29 am    Post subject: Reply with quote
neildlr@gmail.com wrote:
. . . I am having trouble removing the screws on the grip and do not want to damage them. Do you think the issue is with the focus assembly?


Yes, I think the focus assembly is your problem. And for me personally, it'd be difficult - if not impossible - to reassemble a focus helicoid without taking the outer pieces off.

So if it were my lens, job #1 would be to get the focus grip off. And it appears that the depth of field scale trim piece will need to come off before the focus grip will..?

And you're dealing with stuck screws? Assuming you have properly fitting screwdrivers, I think patience is the key. It's good you're being careful.
Applying heat to stubborn screws often works for me. A hair dryer or even a soldering iron should help. I must admit I don't know what temperatures are safe - I just heat the screws until they're good and warm.

Perhaps in some cases a penetrating oil might help? I've rarely used oil and don't know much about that. I've also read gentle tapping of the screw head can sometimes help to loosen a screw. If you need a better grip on the driver, you could wrap a rubber glove around the handle.

If a solvent is needed for glued screws, isopropyl alcohol is relatively gentle yet effective. Sometimes I resort to acetone.


PostPosted: Mon Aug 09, 2021 8:00 pm    Post subject: Reply with quote
Ok, after spending the entire day with this lens and with my brother's help, we managed to reassemble most of it. The grip was clearly attached at the wrong point to the thread, which we have fixed. The lens can now focus to around 200m when it is on the infinity mark, and the travel seems to be close to correct. I think the only fine tuning I still have is to remove and re-start the mount end at the correct point along the thread. So a bunch of trial and error.


PostPosted: Mon Aug 09, 2021 8:44 pm    Post subject: Reply with quote
Like 1 small

I'm happy to hear you figured it out.


PostPosted: Tue Aug 10, 2021 5:44 pm    Post subject: Reply with quote


I managed to find the sweet spot and correctly thread the focus assemble back on to the lens. The length is correct, and I tested the infinity focus on a building approximately 2.5km away. The lens seems sharp enough, and contrast gets decent from f16. Thanks everyone for your help!



PostPosted: Tue Aug 10, 2021 7:07 pm    Post subject: Reply with quote
Like 1 Like 1 Congrats Whoo Turtle
Wow that's a long lens
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