Thoughts on "Multicoated" lens filters

On Aug 11, 4:08 pm, Tony Polson wrote:
(D.M. Procida) wrote:
Dave wrote:

should i buy "Multicoated" lens covers (i believe a.k.a. Neutral
Density Glass Filters)? has anyone used them?

And, if the miraculous (so people keep saying) Pentax SMC lenses have
the best coatings, wouldn't Pentax filters (if indeed there are any such
things) be the best?

There was a time when Pentax SMC coatings led the world. But that was
a long time ago. It predated the change from M42 mount to Pentax K
bayonet.

Pentax licensed the technology to other companies, notably Nikon and
Carl Zeiss. Further development of coatings has led to improvements
beyond the original SMC, and Pentax no longer holds a clear lead (if
any at all) over other brands.

Proof? Has anyone done transmission and reflection tests on current
anti-reflection coatings?
If you look at two of the same lenses and see a slightly different
colour to the coatings, that means the process is not 100% and you
really don't know if the coatings are as good as claimed.
Additionally, some multicoatings are worse than single mag-fluoride
coatings because if they are not done precisely, they can exaggerate a
poor optical polish because they are irregular. I don't know about
camera lens coatings, they are changing all the time because of
digital sensor requirements, but Pentax's last generation of SMC
coatings and Zeiss's coatings applied to military optics built in the
Jena facilities in the 1990s are about as good as you can get.