Lens coatings.

[fidget]

When looking at the reflections from a lens, say a collection of J8s, the late models have lovely Disney-colour reflections, blues, purples and yellows apparently at varying depths within the lens. Some lenses, like my old J8 or even some newer H103 for example have a much more muted set of reflections, maybe only on or two of which have any colour and then usually blue.
Is this because they are not multicoated? Is this how you can determine?


Dave.....

 

[Xmas]

The simple answer is the pre WWII process was single layer and the colour was exactly like a soap bubble or oil film.

With multi coating they can do anything they want like make narrow band filters, IR filters etc. complicated.

When you look into a lens you should see the coating on each air to glass surface, which you seem to have observed.

Noel

 

[fidget]

So, would your average FSU lens (J8,H103) ever have been single coated?
what reflections would a single coated lens give, or is it so variable as not to be easy to see?


Dave...

 

[fidget]

I thought that i might try a no/single coated lens when I expect high contrast. A 58 J8 I have shows very little other than a single blue reflection from the top lens and one at the very bottom. The H103 and Menopta I have show a weak colour, so could be single coated?
I was beginning to think that I need a 40mm Nokton SC when I remembered the Kiev lenses I am shaping up to sell. I could resurrect the Kiev and try a few.

Dave..

 

[Xmas]

The J8 just post war used the Zeiss process, so they will be single coated, multi coating was later, first military e.g. Apollo (moon). The Kiev plants wont have used multi coating as early as the Ja manufacturers, post '75 or later.

The colour of a single coating is dependent on the thickness of the coating just like oil or soap film. And it will be easy to see compared with multi coating.

Window glass reflects about 4% at normal incidence, Single coating reduces this to 1%, approximately, the colour is the 1% residue, the eye only sees the dominant residue. Multi coating reduces this further, the colour from multi coating is a much smaller residue. So the colour is less critical the amount is what counts.

Multi coating can be slippery, really hard and really difficult to clean.

The late optics are all probably multi coated.

The noctilux f/1 is a conventional design made possible by multicoating, Leica use a very high refractive glass which needs less spherical surfaces, it is the spherical surfaces which cause the abberation, but the reflection is dependent on the refractive index so the lens would be all flare and no transmission from the very high refractive index glass, if leica did not use a sophisticated multi coat on every surface.

The current aspherical lenses were later and use aspherics to avoid the spherical limitations. The earlier 1.2 Noctilux was really difficult to make, their expert could only make a lens on his good days, rejects on mondays and fridays...

Noel

 

[Xmas]

We double posted sorry

The J8 was designed pre coating with low refractive index glass, its was cloned from the sonnar which is high contrast, because it has only six air to glass surfaces, and is nicely masked for flare, e.g. by physical internal arrangement, curvature of optics etc. The FSU tended to not use black paint on principle in some factories and some J8 need rebuilding to get optimium performance wide open, dont worry they will still out draw a Summitar or Summicron of the same period for contrast and flare.

Noel
P.S. I prefer the sonnar or J8 for night shots, if you drop a J8 it is not a tragedy.
P.P.S. selling J8's me me me me me me me