"Canon says...."

On Wed, 4 Jan 2006 20:47:09 -0500, "Charles Schuler"
wrote:


"Rich" wrote in message
.. .
That reflections off digital sensors are an issue and that the
coatings (Super Spectra) on their "L" lenses help minimize this
problem. The coatings help guard against ghosting and reflections.
I wonder if they developed this coating recently?
Rule of thumb with lens coatings is that if they look dull brownish
or greenish and not much light is coming back from reflections,
the coatings are probably pretty decent. If you see multiple images
reflected in each element and they are in any way "bright" the
coatings are probably poor.

Are these coatings applied to the Canon EFS lenses?


I don't know. It was in an ad for the "L" lenses.
-Rich

On Wed, 4 Jan 2006 19:29:59 -0700, "Steve Wolfe"
wrote:

Are these coatings applied to the Canon EFS lenses?

All modern lenses are coated. However, there are differences between
coatings and coating technology. For instance, multicoated lenses generally
have much lower reflectance than single-coated, but even within the single-
or multi-coated world, there are differences in which coatings are used, and
in how uniformly they are applied, the thickness of the coating is very
important. And like any other part of lens manufacture, if something will
make a better lens, they're going to charge you more for it - even if it
doesn't necessarily cost them more to do it.

As to why all modern lenses are coated, an uncoated element can cost you
as much as 10% of your light, and cuts into your contrast as well as your
intensity. Work out the numbers on just how much you'd lose on a 10-, 13-,
or 15-element lens if they weren't coated! The highest quality coatings can
achieve a little upwards of 99% transmission.

steve


True. At a raw lens surface, 4% of the light is reflected. Through
destructive interference, with single-coated surfaces, about 2% is
reflected. Multicoated surfaces (as you said, if applied correctly)
are very efficient.
However, manufacturers will be using more exotic lens curves to
eliminate extra elements that are needed now because most lens
surfaces are spherical. After passing 28 surfaces, even coated to
99% reflectivity, you are experiencing light and contrast loss on
a pretty big scale.
-Rich

On Thu, 5 Jan 2006 03:07:34 +0000, Kennedy McEwen
wrote:

In article , Rich
writes
That reflections off digital sensors are an issue and that the
coatings (Super Spectra) on their "L" lenses help minimize this
problem.

Canon also say that the reason that they cannot do OTF TTL flash
metering, which they did use on film cameras, is because the light
reflected off the digital sensor is significantly less than that
reflected off film.

This apparent contradiction is simply explained by the fact that the
design modification to the TTL metering is made by engineers whilst the
spin about lens coatings is made by marketing. The AR coating would be
even more effective on film than they are on digital sensors and is only
a wide band multi-coating in any case.

The coatings help guard against ghosting and reflections.

That is always the intention with AR coatings.

I wonder if they developed this coating recently?
No, unless you call 30 years ago recent.

They didn't have multilayer coatings that long ago, only single-layer
magnesium-fluoride coatings which produce that typical blue hue
seen on reflection from older lenses.
-Rich

On Wed, 04 Jan 2006 19:08:22 -0800, Randall Ainsworth
wrote:

In article , Rich
wrote:

That reflections off digital sensors are an issue and that the
coatings (Super Spectra) on their "L" lenses help minimize this
problem. The coatings help guard against ghosting and reflections.
I wonder if they developed this coating recently?
Rule of thumb with lens coatings is that if they look dull brownish
or greenish and not much light is coming back from reflections,
the coatings are probably pretty decent. If you see multiple images
reflected in each element and they are in any way "bright" the
coatings are probably poor.

Maybe you can tell us more when you actually own a camera?

Watch it, Randall, second-place is still open.
-Rich

On Thu, 5 Jan 2006 04:40:00 +0100, "Bart van der Wolf"
wrote:


"Rich" wrote in message
.. .
That reflections off digital sensors are an issue

Are they?

Reflections will have passed (twice) through a CFA filter array, and
through the Anti-Reflection coating of the sensor cover glass, before
they'l hit the lens' rear lens again.

Bart

Not if they are reflected directly off the front of the cover glass.
Anyone know what the reflectivity of that is?
-Rich

In article , Rich
writes

They didn't have multilayer coatings that long ago, only single-layer
magnesium-fluoride coatings which produce that typical blue hue
seen on reflection from older lenses.

Absolute crap, of course they did - look at all those SMC Pentax
Takumars that were produced in the 1970s for example. "SMC" *is* the
Pentax monogram on Super Multi Coated lenses!

The first lens I bought for my OM-1 back in 1974 was a 50mm f/1.8 which
was multicoated (albeit not on all elements) as can be witnessed from
their green reflection. Olympus started using the MC nomenclature on
their lenses around 1982 to differentiate those which were multicoated
from those which weren't, but as any long term OM user knows, they had
been using MC on their lenses long before the marketing department
decided to make an issue of it. Other manufacturers, eg, the Pentax
example above, were making the distinction long before Olympus followed
them.
--
Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he's ****ed.
Python Philosophers (replace 'nospam' with 'kennedym' when replying)

dfs writes:

I wonder if they developed this coating recently?
No, unless you call 30 years ago recent.

They didn't have multilayer coatings that long ago, only single-layer
magnesium-fluoride coatings which produce that typical blue hue
seen on reflection from older lenses.

I can still remember the Pentax ads when they introduced their SMC
(Super Multi Coating) process, which was a 7-layer coating. Google says
this happened in 1971. At that point, other camera manufacturers were
using 3-layer coatings. I still have some of those lenses. You can
tell that they are not single-layer coatings.

So we've had 7-layer coatings on consumer lenses for 35 years, and the
3-layer multicoatings go back further than that.

Dave

In article , Dave Martindale
writes
dfs writes:

I wonder if they developed this coating recently?
No, unless you call 30 years ago recent.

They didn't have multilayer coatings that long ago, only single-layer
magnesium-fluoride coatings which produce that typical blue hue
seen on reflection from older lenses.

I can still remember the Pentax ads when they introduced their SMC
(Super Multi Coating) process, which was a 7-layer coating. Google says
this happened in 1971. At that point, other camera manufacturers were
using 3-layer coatings. I still have some of those lenses. You can
tell that they are not single-layer coatings.

So we've had 7-layer coatings on consumer lenses for 35 years, and the
3-layer multicoatings go back further than that.

And technology itself was available and used long before that for
specialist optics but it only became cost effective enough to use on
standard camera lenses in the past 30 odd years.

I doubt that many of the cameras on the Apollo, Gemini or Mercury
programs were single or even triple layer coatings, given the extreme
contrast subject material they were used to photograph.
--
Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he's ****ed.
Python Philosophers (replace 'nospam' with 'kennedym' when replying)

On Fri, 6 Jan 2006 04:34:45 +0000 (UTC), (Dave
Martindale) wrote:

dfs writes:

I wonder if they developed this coating recently?
No, unless you call 30 years ago recent.

They didn't have multilayer coatings that long ago, only single-layer
magnesium-fluoride coatings which produce that typical blue hue
seen on reflection from older lenses.

I can still remember the Pentax ads when they introduced their SMC
(Super Multi Coating) process, which was a 7-layer coating. Google says
this happened in 1971. At that point, other camera manufacturers were
using 3-layer coatings. I still have some of those lenses. You can
tell that they are not single-layer coatings.

So we've had 7-layer coatings on consumer lenses for 35 years, and the
3-layer multicoatings go back further than that.

Dave

You are right. After I'd posted it, I remembered seeing a Nikon
microscope eyepiece from those days that was multicoated.
-Rich

"Kennedy McEwen" wrote in message
...
In article , Rich
writes

They didn't have multilayer coatings that long ago, only
single-layer magnesium-fluoride coatings which produce that typical
blue hue seen on reflection from older lenses.

Absolute crap, of course they did - look at all those SMC Pentax
Takumars that were produced in the 1970s for example. "SMC" *is*
the Pentax monogram on Super Multi Coated lenses!

Obviously true, and e.g. the instructions with my Canon FD lenses from
the 70's (approx. early 1973) said: "Furthermore, the use of
multilayer antireflection optical coatings and the adoption of Canon's
unique focusing mechanism have contributed to the strengthening of the
series of FD lenses".

For example,
http://www.canon.com/camera-museum/camera/lens/fd/data/fd_50_14_sscv1.html
(SSC was Super Spectra Coating).

It was already becoming quite common in those days.

Bart