Tamron 400mm 6.9 T-mount (M42 adapter) & Nikon D90 probl

jazzper · Joined: 29 Oct 2013 Posts: 6 Location: Netherlands

I use some M42 lenses like a Komine 135mm 2.8, Yashinon 50mm 1.4 DX and Kenlock 28mm 2.8 on my dSLR bodies (and on analog but that is a different story). For my Nikons (D90 and D70) is use a $10 taiwainese M42>F converter with correction lens for infinity focus. For a Canon 300D (I'm a Nikonian but got this one almost free...) I have a simple M42>EF adapter with no lens (but has a chip!).

Recently I bought a Tamron 400mm 6.9 adaptall for 10 euro. This exact lens and examples of its potential are discribed in this topic by Luis: http://bit.ly/17pF3pd

I had to refurbish it a bit. A stuck and dirty UV filter had to be removed in a destructive way and luckily the lens can be unscrewed at different levels so I could easily clean the uncoated lenses with 70% alcohol. The lens is shiny again and no scratches!

Alright... the problem: it seems I can't get infinity focus. The lens starts at 9 meter (as documented) but ends already at let's say 40 meters...

Here an example of a pole at 20 meter:

Nikon D90
ISO 640, 1/500th and I guess apperture full open (6.9)

Not razorsharp but conditions were crap (monopod in my car on the soft seat...) and stormy weather.

Anything much further wont focus. Any clues?

edit: what's wrong with the bb-code? I cant paste url's correctly. with or withour URL tags.

Lloydy · Expire: 2022-01-01

jazzper · Joined: 29 Oct 2013 Posts: 6 Location: Netherlands

Thanks! That explains it. This forum is really afraid (or prepared) for spam isnt it? I almost did not pass the registration human test Smile

edit: ah! with this second post I was able to edit my TS

luisalegria · Expire: 2018-01-18

Is the problem that the barrel won't turn all the way to the infinity mark, or that at "infinity" it only goes to 40m?
There are several problems that can be caused by reassembly of a lens, if not everything is back in precisely the right place. Spacing of elements in a multi-element tele like this is critical. Losing infinity focus and loss of resolution are among them.

jazzper · Joined: 29 Oct 2013 Posts: 6 Location: Netherlands

Thanks. I did not remove the lenses itself. Just the 3 parts the whole lens body consist of. And yes I can turn al the way to infinity (well on the markings).

Andrew G. · Joined: 18 Jul 2010 Posts: 159 Location: Pennsylvania, USA

I believe the problem here is the assumption that you're using an M42 T-mount with a Nikon body... don't do this. You want a Nikon T-mount for infinity focus.

luisalegria · Expire: 2018-01-18

Ah, didn't catch that.
If the Tamron has an M42 T-mount and you are just screwing it into an M42-Nikon adapter you will not get infinity focus.
The problem is that the Nikon mount register is @ 1mm deeper than M42. No M42 lens will get infinity on Nikon.

Fortunately this is a T-mount lens and you can merely swap the T-mount for a Nikon version (has a proper Nikon bayonet instead of the M42 screw, and is 1mm shallower). That should fix you up.