Recoated collapsible M summicron 50/2.0

[Universalb50]

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I have a lens that was recoated years ago (Selten), and remains "perfect'. Can I assume the recoated lens will be comparable to an original in resolution?

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[spydrxx]

The coating shouldn't really alter the resolution, but rather the contrast and flare resistance.

[TomB_tx]

Any polishing to re coat, or care in reassembly can affect resolution.

[spydrxx]

Tom's right. I made my comments assuming no polishing of the glass was necessary, merely recoating.

[Ecar]

It depends on what one calls "comparable".

For example, several years ago, I sent an old Summar to Peter Grisaffi for a CLA.

The lens had a sentimental value for me and the front element showed numerous, thin surface scratches.

Upon advice from Peter and the company who did the glass work for him, we decided to have the front element polished and recoated.

My understanding was that the effect of the polishing process using modern technology would remove only a negligible amount of the glass surface and that it would, if anything, correct the irregularities of glass produced using industrial processes from decades ago.

I guess that what I'm saying is that old lenses of the same type are not strictly comparable between them due to production variances and that polishing the front element only is unlikely to alter the resolution of a lens in a way that would make it "different" from its peers.

On the other hand, while recoating per se does not affect resolution, it has a fairly dramatic effect on the rendering of a lens - indeed by improving contrast and flare resistance.

That Summar is now probably a significantly "better" lens than it was out of the box - but has arguably lost some of its character.