Drastic fine focus adjust

[Pistnbroke]

I had a Tokina  80-400  with off the scale fine focus ......removed the mount and stuck 3 bits of 5 thou feeler gauge under the mount and re fitted it ...fine +10
Sold it

[richardHaw]

Nikon actually use washers for this. 

[David H. Hartman]

Nikon actually use washers for this. 

Washers, not a shim in the shape of the bayonet??? That sounds sleazy to me.

Dave

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I've head of people adding a paper shim to make a zoom lens more parfocal. This probably in the era of manual focus zooms. I don't remember and I've never tried it.

[Erik Lund]

Yes it's called 'shim' when it's for the lenses, and it's 'washer' for the sensor adjustment. When you talk of how Nikon does...

Sounds like this case, Tokina DIY was plain washer quick and dirty fix



Not recommended to fool around with shimming lenses with IF or CRC,,,

[richardHaw]

yes, shim 

[David H. Hartman]

Can one buy copper or brass in sheets in thousandths of an inch or in fractions of a millimeter (microns) to cut a proper shim from?

Why not shim an IF  or CRC lens? Would other adjustments be needed or might there be other complications? If you will please enlighten my ignorance.

Dave

[Erik Lund]

Can one buy copper or brass in sheets in thousandths of an inch or in fractions of a millimeter (microns) to cut a proper shim from?

Why not shim an IF  or CRC lens? Would other adjustments be needed or might there be other complications? If you will please enlighten my ignorance.

Dave

The can of course have shims out of the production line.

But when you add additional 'extension' shim or extension tube to an IF or CRC lens, you put the optics out of the optimum/calculated working range - All the nice 'build in' corrections are crippled and you get all kinds of aberrations and field curvature issues,,, This is much much less for most unit focusing optics.

[richardHaw]

i find that this shim/washer thing is much more common on zoom lenses

i do not know if anybody remember this: back in the days when the 24-70 had a weak F-mount issue, Nikon would recall these lenses and fix the or reinforce the mount. many users actually noticed that Nikon added some shims on their lenses. this is probably used to compensate for some focus shift

zooms change geometry, much like CRC as you zoom back and forth and it can be difficult to fix any film plane to exit pupil distance problem so the shims may be used as a cheap measure to fix that This is just me guessing by the way.

it is also interesting to note that this was employed more towards the Ai-S era and I found the E-series of lenses to have the most.

[Erik Lund]

i find that this shim/washer thing is much more common on zoom lenses

i do not know if anybody remember this: back in the days when the 24-70 had a weak F-mount issue, Nikon would recall these lenses and fix the or reinforce the mount. many users actually noticed that Nikon added some shims on their lenses. this is probably used to compensate for some focus shift

.....

I don't recall any F-Mount issues with 24-70mm AFS,,, ?

Are you thinking about the by design breakaway 'safety plate' inside the lens?

Sure if you mount another bayonet mount, if there is any variance in machining you just add shims to stay within the tolerances, perfectly normal.
Also a 'in lens'AF fine tune for the lens is done if it has been disassembled - reassembled,,,

No, not for focus shift IMHO

[richardHaw]

sorry, i was referring to manual lenses like the 80-200 f/4 and the 100-300 5.6

when the 24-70mm first came out, for the 1st to 2nd year, Nikon got a lot of heat when the 24-70s start breaking near the f-mount for very little reason at all. if i am not mistaken, it was a Russian photographer than started all this when he found his lens in 2 pieces inside the bag (while mounted on a D700, i think) and this led to other similar cases and the birth of "impact damage" alibi from Nikon started. the internet is such a powerful thing this was at dpreview i think, possible 2008?

[Erik Lund]

......zooms change geometry, much like CRC as you zoom back and forth and it can be difficult to fix any film plane to exit pupil distance problem so the shims may be used as a cheap measure to fix that This is just me guessing by the way.
....

When you design the lens; Zoom CRC IF or the like you leave in room for the shims just like for the sensor in the camera. then when you put together the pieces you measure the whole assembled lens or camera and then you adjust the amount / thickness of shims needed. And other adjustable means...

There are additional ways you do this also, measuring the optical cells and the focusing units and selecting the ones that fit best together - You can find these measurements inside the lenses on the various 'building blocks' 
This is also done on rangefinder lenses where the tolerances are super important to relay the distance to the rangefinder unit form the particular lens in use,,, Part of what makes Leica M lenses very expensive!

[Erik Lund]

sorry, i was referring to manual lenses like the 80-200 f/4 and the 100-300 5.6

when the 24-70mm first came out, for the 1st to 2nd year, Nikon got a lot of heat when the 24-70s start breaking near the f-mount for very little reason at all. if i am not mistaken, it was a Russian photographer than started all this when he found his lens in 2 pieces inside the bag (while mounted on a D700, i think) and this led to other similar cases and the birth of "impact damage" alibi from Nikon started. the internet is such a powerful thing this was at dpreview i think, possible 2008?

This was by design a breakaway 'safety plate' inside the lens!

Several large pro lenses has this feature.

The lens can be repaired in few minutes - since the whole rear of the lens is available as a spare part incl. mount and CPU and wiring.

[richardHaw]

When you design the lens; Zoom CRC IF or the like you leave in room for the shims just like for the sensor in the camera. then when you put together the pieces you measure the whole assembled lens or camera and then you adjust the amount / thickness of shims needed.

all i know is the one for the sensor. i was talking with a tech once and he told me NEVER to adjust these he worked at Nikon and they used special software for this. the same reason why i stay away from newer German cars and prefer the classic MB's or Italian ones everything you do on a modern BMW needs some diagnostics with a laptop

[richardHaw]

I see, like a lizard's tail

https://www.dpreview.com/forums/thread/2280430

if i am not mistaken, this is the post that started the minor panic

it was early 2008.

i cannot reveal who told me but this part was silently reinforced by Nikon.

[Erik Lund]

all i know is the one for the sensor. i was talking with a tech once and he told me NEVER to adjust these he worked at Nikon and they used special software for this. the same reason why i stay away from newer German cars and prefer the classic MB's or Italian ones everything you do on a modern BMW needs some diagnostics with a laptop

Well,,, if you replace the sensor/cover glass/AA filter pack you should also check/adjust the shim thickness on the camera and recalibrate the in-camera AF sensor correction values! - So effectively it's the identical to a lens!

Yes, you should never do this yourself! That's what I started out with stating in my first post