Lens dissassembly, assembly, optical benches, et al.

[Leigh B]

What am I missing here?

Binning.

All manufactured components have tolerances. Binning is used to minimize the impact of those tolerances on product quality.

Speaking here of high-end photographic lenses, not the junk you buy from some mass retailers who could care less about quality.

Any manufacturer of precision equipment uses binning to select which specific parts will work best with which other parts.

One common measurement for a lens cell might be the distance from the mounting face to a principle plane.
Depending on the quality of the particular lens, these might be graded as nominal, +0.1mm, -0.1mm, etc.

Other major groups of the lens are similarly binned.
So a front cell that's +0.1mm would be assembled with a barrel that's -0.1mm to achieve the correct overall dimensions.

This is universal practice in precision assembly.

The net result is that any particular sample of the product that you pick up would already have the selection made,
so you could likely dis-assemble and re-assemble it without seriously disturbing its performance.

Now, can you provide some published substantiation for your assertion that manufacturers lack proper measuring equipment?

If not, you're just blowing smoke.

- Leigh

[clayne]

When did I say that manufacturers lacked measuring equipment? I don't remember saying that. All I meant is that with a single sample of a lens there typically won't be anything to adjust other than focus' reference to infinity.

Basically there's no way for a user to adjust alignment of elements if the lens barrel assembly has zero facility for doing so. The only thing the user can do is follow strict disassembly/assembly protocol. I think that's a pretty sane assertion.

The whole point of this thread is in breaking down the bullshit protectionist mysticism surrounding camera and lens maintenance.

[mtjade2007]

I once picked up a Rollie medium format projector from a flea market for $15. The reason it was so cheap was the zoom lens for the projector came in a bag of a dozen or so of glasses and an empty lens barrel. I figured in the worst case I would have to find a replacement lens for the projector.

Well, I tried all possible combinations of orders and the sides of all the glass pieces to reassemble the lens. Some of the glasses due to the size were obvious. So there weren't too many possible combinations to try. Within one hour I found a combination that would project a sharp image on the screen. I then cleaned each piece of glass and reassemble again. I have had a perfect Rollie MF projector ever since.

I guess to some people as soon as the lens is disassembled and the glasses mixed up it becomes a paper weight. Not really.

[benjiboy]

I once picked up a Rollie medium format projector from a flea market for $15. The reason it was so cheap was the zoom lens for the projector came in a bag of a dozen or so of glasses and an empty lens barrel. I figured in the worst case I would have to find a replacement lens for the projector.

Well, I tried all possible combinations of orders and the sides of all the glass pieces to reassemble the lens. Some of the glasses due to the size were obvious. So there weren't too many possible combinations to try. Within one hour I found a combination that would project a sharp image on the screen. I then cleaned each piece of glass and reassemble again. I have had a perfect Rollie MF projector ever since.

I guess to some people as soon as the lens is disassembled and the glasses mixed up it becomes a paper weight. Not really.

People only post about their successes, not when they have made paperweights of them.

[Steve Smith]

Speaking here of high-end photographic lenses, not the junk you buy from some mass retailers who could care less about quality.

Couldn't care less?


Steve.

[Leigh B]

Couldn't care less?

No, they could care less. I'm sure they care about it when they go shopping for a new car.

They just don't care about it as regards their own products.

- Leigh