On Tue, 14 August 2001, "John A. Lind" wrote:
>3. That first coating makes an enormous difference compared to zero
>coating, especially on a prime lens with no more than 5 to 7 elements.
(snip)
>4. Multi-coating only makes a very minor incremental improvement over a
>single coating, especially on prime lenses. The efficacy of a single
>coating is also affected by the refractive index of the glass used. Higher
>index glass, as is often used in the better Zuiko's, decreases the gain
>made over single coating by going to a multi-coating.
>5. I'll stack my mint-minus, ca. 1954 **single-coated** 50mm f/1.5 Carl
>Zeiss Sonnar with its 7 element, 3 group formulation that was created in
>1932, against anything multi-coated they can muster from Can*n, Nik*n,
>Pent*x, or Min*lta, in contrast, sheer resolving power, flatness of field,
>flare control and absence of pincushion or barrel distortion.
My medium format cameras (6x9cm) and lenses are relics from the '50s, '60s and
'70s. Only one lens out of more than a dozen is multi-coated -- a Schneider
Symmar S. All the others are single-coated, and these old lenses, Zeiss
Planars and Sonnars, Schneider Xenotarrs and Symmars, Rodenstock Grandagons and
Rotelars, are the biggest bang for the buck anywhere. Most of them I picked up
for less than $300 each, some for less than $200, and the most I paid for any
one of them was $400, and I think they, like John?s old Sonnar, will more than
hold their own alongside the Nik*ns, Can*ns, et al.
There was a very good article in a recent issue of "Shutterbug" on lens design,
and I?m quoting below a couple of relevant paragraphs on the subject of lens
coating.
"The jump from coating to multi-coating is nothing like as great as the jump
from uncoated to coated lenses, but when you are dealing with lenses having
perhaps 15 glasses in 10 groups, even small improvements are welcome. Take a
simple uncoated lens such as a Tessar, with six air-glass surfaces and 95
percent transmission (5 percent reflection) at each: you are looking at 0.95
raised to the 6th power, or 74 percent overall transmission. This is
acceptable, but not brilliant. Single coat it and get the transmission up to
98 percent at each interface, and it has 89 percent transmission overall. The
difference between this and a 99.5 percent transmission at each interface,
giving 97 percent overall, is not normally worth worrying about.
"Multi-coating is shamelessly used as a marketing ploy, even to the extent of
multi-coating lenses that don?t need it. This does no harm, but it is spending
money needlessly. Serious designers are more likely to multi-coat some
surfaces and single coat others."
Walt
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