On 30 Sep 98, at 3:51, Joseph Albert wrote:
>
> Shawn and/or Janis writes:
(it was Shawn!)
> 85/2
> Primary reflections: Pale green, purple, yellow.
> Secondary reflections: Purple, yellow <- from SC element?
>
> 50/1.8
> Primary and secondary: Blue, Purple, Yellow
>
> 35/2.8 and 135/3.5 both SC:
> Purple, yellow.
>
> ================================================
>
> the 85/2 is multicoated if there is green. the colors in the sequence
> correspond to layers not elements. it is doubtful that some elements
> are single coated in a multicoated lens. the 50/1.8 sounds like it
> is multicoated, but have to be sure the blue isn't purple. actually,
> I can't substantiate but tend to believe that the early multicoating
> of olympus had blue, purple and amber, and green indicates a later
> coating formula.
I was assuming the groups of reflections in the Green-Purple-Yellow
sequence, were different layers on one element. But in each case, I also get
a second sequence of reflections leading in a different direction to the
primary, most prominent one. In the case of the 85/2, this secondary
sequence seems to lack any green or blue, which is why I noted the
possibility of a SC element.
The blue in my 50/1.8 is a pale blue, quite different from the green and purple
hues. I do know that the 50/1.8 was new in 1985, but have no knowledge of
the 85, so it *could* be newer it could be newer than the 50.
<snip>
Thanks for the information background on the coating process!
Shawn.
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