[mkirk]

Anyone know of a service manual or could tell me how to adjust infinity focus on a Tokina 19-35mm lens?


My copy *just* misses infinity by a little bit and I've adjusted Pentax lenses in the past and that was simple to do, but this Tokina is assembled differently, so peeling back the rubber grip and adjusting some screws isn't going to work (I already tried ). This lens was is the same design made/marketed by Phoenix, Vivitar, and some others. Any help is appreciated!



Lens in question: Tokina AF 19-35mm f/3.5-4.5 (193) Lens Reviews - Tokina Lenses - Pentax Lens Review Database

[maw]

Hi mkirk,

I own the same lens, purchased in Germany new, but it is branded Vivitar, and it is silvered.
Vivitar Series 1 19-35mm F3.5-4.5 Lens Reviews - Vivitar Lenses - Pentax Lens Review Database

What you should do is be very patient and adjust the front/back focus, being a very short focal length (on FF), it is difficult, to find the exact point, even if you have the calibration tool.

Mine works perfectly and is very sharp. Try and try again don't give up.

[Joetitch]

This solution might give infinity if it is because back/front focus. Won't work if Lens is physically "short".
I have pulled one of mine apart and cannot remember if there is any adjustment possible. I think it is possible to remove the part that the hood fastens too but you might have to get right inside to make any adjustments to the focus throw.
Sometimes a filter will impact focus so make sure to test without.

[mkirk]

I'm using it on a K1000, so I don't have a back focus adjustment on the camera. :| As far as the filter goes, I have a UV filter on it, but I don't believe it's preventing the element from focusing correctly. I'll double check...

[mkirk]

Nope. The element isn't limited by the UV filter. It just needs a tiny adjustment to get to infinity, which bugs me! LOL So close, so close.

[Joetitch]

Apart from walking closer to infinity another suggestion is as you are using manual focus, if you remove the mount, sometimes it is possible to remove the screw drive rod which might allow the front to rotate that fraction more if it is the drive gear running out of rack length. It is more than 15 years ago that I dismantled mine so I can't be certain that this is a possibility.
The question on the filter had more to do with optical interference rather then physical. I personally have given up on filters unless absolutely necessary for a given situation as I found a to me perceived lack of sharpness when using them. YMMV