Guessing Lens Design Without Disassembly

Started 2 months ago | Discussions thread
fferreres Veteran Member • Posts: 3,746
Re: Guessing Lens Design Without Disassembly

Tons o Glass 0 Class wrote:

fferreres wrote:

I sometimes count based on the very small dust specks. Under a bright light, specks on different layers have to move at a different speed as I rotate the glass. Triplets or doublets: not possible for me to detect so far (of course the most minimal separation would tell it).

With less than 20/20 vision after correction (perhaps having poor vision is one of the reasons why I'm fascinated with optics in general), I'm not sure that I'll be able to use this method myself. Thanks for the tip, though! As we all know, these vintage lenses have at least a few dust specks in them so it sounds like this method could work.

I use it mostly to determine where exactly is haze or fungus or oil vapor before I embark in anything. I think reflections would be more accurate but I still don’t do it very well.

With this method usually you need to identify two dusts nearby that when you turn the lens one crosses the other. If they are the same surface they never cross. Light needs to be strong but not too strong as it can be bad for your eye. The reason I do this is not because it’s best, but in assessing if I will be able to clean and where are the problem areas. I can also sense the shape of the glass by how particles displace, to some extent.

If I can, I try to not look to much and let it be. You always find things when you look too hard!

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