Vivitar 35mm 2.8 - help with infinity and optical diagram

[PhantomLord]

Hello,

Recently I bought Vivitar 35 2.8 in M42 made by Tokina for my 600d and I found out it is quite not sharp in the corners at 5.6 (on APS-C). What's more, today I found out it won't reach infinity, so there is possibility that somebody tampered with it.

I'm looking for optical diagram/schematic for this lens to check if everything is in place and any help/suggestions about adjusting infinity.
I did adjust infinity on Pentax-M 50 1.7 and Fujinon EBC 55 1.8 without any problems, so I hope there will be no problems with Vivitar as well. However any experience is welcome.

This is the lens in question:

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[buerokratiehasser]

Is it pretty heavy for a m42 prime? Super Carenar paperweight?

Also if you are used to adjusting infinity on all m42 lenses, it may just be your m42 adaptor that doesn't quite do infinity? A hama quality product perhaps, like mine for M-AF?

[PhantomLord]

Well adaptor is fine, pentax-m was on pk mount fujinon was in terrible state with sand in the helicolid, so after disassembly and assembly I had to adjust infinity as well.

As I found some info on mflenses and flickr this vivitar is quite nice at least Tokina build.
Still I'll adjust infinity and see how it performs.

[casualcollector]

[PhantomLord]

I adjusted infinity!

To be honest I really don't know how I done it.
Usually adjusting infinity means unscrewing a few screws that holds focusing ring to the helicoid, turn a little bit, tighten screws, try it and repeat to achieve the best results.

In this lens there wasn't any possibility to turn focusing ring separate from the helicolid. I dissasemble almost all of it, assemble it again, and infinity was great, but the dof-scale was completely out of place in connection to the aperture ring. What's more dof scale is as well limiter for the focusing, so when I put it in place in connection to the aperture ring, it doesn't focus properly.
All in all, spend 3hours on it, disassemble and assemble it about 10 times trying different combinations of everything I could turn and voila! It worked. Infinity is bang on, dof scale is in place in connection to aperture ring.
One problem solved.

While disassembling for first couple of times I noticed that rear lens is loose, so at the end I tighten it in place. I checked 3 out of 5 group of lenses and they look like placed properly. However, quick test shot shows that corners at f/4 are softer than on Tamron 17A 35-70 3.5 zoom at according focal length and aperture.
I will test it once again (now with this fancy infinity feature ) in real life shooting and I will see. If it's not better than Tamron not SP zoom than I think it is not good at all.

I'll post some pictures in another thread soon.


Any suggestions in terms of sharpness would be appreciated.

[casualcollector]

I hearty "Well Done" on being brave and getting the infinity problem sorted. I suspect your resolution problem is a mis-spaced or de-centered element.

[PhantomLord]

Thank you.
I hope it is something with placing of the lens as it is quite easy to repair instead of being just rubbish lens .