[Lmuzza]

Hi folks, I picked up a 400mm Tamron popular- but it doesn't seem to be able to focus beyond about 50 metres! Certainly wouldn't focus on the moon or distant hills, any thoughts please?

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Last edited by Unregistered User 8; 02-16-2021 at 08:44 PM.

[Unregistered User 8]

Hi mate. I moved your post in a 9 year old thread to making it a thread of its own for better replies. Good luck.

[luftfluss]

Hi folks, I picked up a 400mm Tamron popular- but it doesn't seem to be able to focus beyond about 50 metres! Certainly wouldn't focus on the moon or distant hills, any thoughts please?

What camera and adapter (if necessary) are you using?

[marcusBMG]

I am pretty sure this is just a generic 400mm f6.3.
How the infinity focus adjusts, or might become out of adjustment, depends on the construction, of which there are different variants. First off, check the objective unit, this often unscrews at the taper. is it fully screwed in, is there facility to adjust. Also check the objective itself, does it look like it has been removed, then not replaced accurately, screwed al the way in?
If thats all ok then the likely culprit is the focus mechanics. Not reassembling the helicoid in the correct thread is a real possibility. Sometimes the focus sleeve is held in place by grub screws and has slipped, or been reassembled in the incorrect place.
Usually these lenses are not difficult to beak down into sections and it should be possibe to figure this out. Post pics and we can help.

[Lmuzza]

Thanks for the suggestions- the lens came with a m42-fx adapter ( I use a Fuji Xt20), I think the adapter is the wrong length? as the thread T2? I have ordered another adapter.

[TwoUptons]

Your lens is likely a T or T2 mount, so it will need an adapter for anything, even M42.

The annoying thing is that the T-mount thread is 42mm.

So you’ll probably need a T-mount adapter straight to your favorite mount. Or a T-mount to M42 then M42 to your mount.

-Eric

[Lowell Goudge]

Your lens is likely a T or T2 mount, so it will need an adapter for anything, even M42.

The annoying thing is that the T-mount thread is 42mm.

So you’ll probably need a T-mount adapter straight to your favorite mount. Or a T-mount to M42 then M42 to your mount.

-Eric

While it is true that T mounts are M42 threads it is a different thread pitch than an m42 screw mount lens.

But missing the adaptor will not cause focus to be limited to 50 meters, it would cause the lens to never focus because it would be mounted closer than infinity. There is something wrong here

Perhaps the OP can post a shot of the mount and back of the lens

[Lmuzza]

It is a T2 mount, I got another adapter & have the same issue! I think the adapters are too thick as I tried holding the lens closer to the camera without a mount & got infinity focus. unless the lens has slipped internally (which I doubt as its in excellent condition) the adapter deign for t2 mount doesn't suit Tamron?

[Lmuzza]

Thanks for the helpful thoughts, a member on a Fuji Facebook page gave me the correct length for the adapter (which the adapter was) but also suggested to check the elements in case one was fitted wrong way round. I took the rear 2 elements out & refitted them (not knowing which way they should go) & the infinity came good. I think the inner element was in wrong way round! Cheers