Richard:
"...Nanocoating, unlike multicoating, is not a continued
evolution of a previous technology...it is indeed an entirely new approach
to solving an old problem. Nanocoating is based on the design of moth eyes,
which are known in the scientific community to have one of the lowest
reflectance indexes of any material. The general design is based on
nano-scale roughly dome/spike-like structures intended to guide as much
light as possible into the lens, avoiding reflectance entirely whenever
possible.If and when flare or ghosting does occur, since nanocoating is not
designed to work on any given wavelength of light but light in totality,
the resulting artifacts or loss of contrast is considerably less than with
a multicoated lens. In many cases, careful and close scrutiny is required
to find small elements of flare and ghosting in photo taken with a
nanocoated lens, and when it does exist, it often does not detrimentally
affect IQ. Transmission levels for nanocoating are at least *99.95% PER
COATED ELEMENT/GROUP*. At a lost of 0.05% or less, the grand total
transmission loss for any lens, even complex lenses with many element
groups, will remain very low (i.e. a complex 15 group telephoto lens would
end up with a total of *0.75% transmission loss*.)..."
https://photo.stackexchange.com/questions/22151/what-does-a-nano-crystal-coat-do-on-this-lens
Nanotechnology is good for the zoom lenses used as standard today, it does
not improve the lens sharpness directly, but it allows _at least_ 99,95% of
light transmission through the lens. BTW, a Tessar, a Xenar, a Planar, a
Xenotar, a Sonnar lenses needn't nanocoatings to improve their performance.-
Carlos
El mar., 27 oct. 2020 a las 15:19, `Richard Knoppow (<dickburk@xxxxxxxxxxxxx>)
escribió:
I wonder how much of "nanocoating" is just sales language.
The theory of coating is very well understood. The application of
coatings that are ideal may be diffcult. Here are a couple of
things: The main purpose of a coating is to improve the "match"
between the index of refraction of two surfaces to reduce or
eliminate reflection. It should be borne in mind that coatings
can also be used to increase reflection, for instance in
telescope mirrors.
The index of refraction of glass is not constant with
wavelength, hence the use of multiple types of glass to
acromatize lenses. A single coating works at one wavelengh and at
one angle of incidence. Since going thorugh the coating at
various angles affects the path length through the coating it
also affects the wavelength of the maximum "matching" or
reduction of reflection. Multiple coatings suffer the same
physical limitations but the effect is spread over a wider band
of wavelengths. It is possible to make a coating with a
continuous variation of index to broaden out the effective range
of color even more than using two or three discreet coatings.
A perfect coating would result in totally eliminating any
reflection. The coated surface would be visible only by means of
its absorption or distortion.
The color of the residual reflection will tell you something
about the coating. It will reflect color where it is least
efficient. Typical older coatings had a blue color because they
were adjusted to have maximum effect somewhere in the range of
green light, early multiple coatings were often green because
there were two peaks in efficiency, one in the blue and one in
the orange or red.
Baked coatings approach optical glass for hardness but,
judging from the number of scratched surfaces one sees the
coatings are softer and generally more vulnerable to scratching.
Also, not all optical glass is of equal hardness. Some is very
hard, some is very soft. What is on the outside of a lens depends
on its design. I don't remember which glass is the hardest and
which is softest but its not too difficult to find out what kind
of glass was used in various designs, for instance, a Tessar.
Lens designers working on designs for consumer devices must keep
in mind that very soft glass must be avoided for exposed surfaces.
Somewhere I got all this stuff either from reading or from
conversations with some practicing lens designers but my memory
is not infinite as I would like it to be (or maybe not, I
remember things I would prefer to forget) so details are often
gone. Left as an exercise for the student, meaning the author
doesn't remember how to solve the equations.
On 10/27/2020 2:10 AM, CarlosMFreaza wrote:
Eric:
I think my lens polishing removed some of the first
element coating only and it was enough to eliminate the
cleaning marks/scratches, they did not touch the glass. I read
somewhere that most of the time cleaning marks are on the lens
coating, not in the glass itself.
Traditional ways to coat and to multi coat lenses are being
replaced by the nano- coating technology today; it has nothing
to do with older processes and it is more efficient to transmit
light through the lens elements by increasing the
anti-reflection effect.
"...Coating Technology Created Through Nanotechnology
The latest technologies are also being used in lens coating.
SWC (Subwavelength Structure Coating), developed by Canon, is a
new type of technology that uses aluminum oxide (Al_2 O_3 ) as
the structural material of the coating in order to align
countless wedge-shaped nanostructures only 220 nm high, which
is smaller than the wavelength of visible light, on a lens
surface. This nano-scale coating provides a smooth transition
between the refractive indexes of glass and air, successfully
eliminating the boundary between substantially different
refractive indexes. Reflected light can be limited to around
0.05%...".
The Leica lens in my Lumix LX7 is nano-coated.
Carlos
El lun., 26 oct. 2020 a las 22:36, Eric Goldstein
(<egoldste@xxxxxxxxx <mailto:egoldste@xxxxxxxxx>>) escribió:
Thanks for the information, Carlos.
Eric Goldstein
On Mon, Oct 26, 2020 at 9:33 PM CarlosMFreaza
<cmfreaza@xxxxxxxxx <mailto:cmfreaza@xxxxxxxxx>> wrote:
>
> Hi Eric:
> I think perhaps you misinterpreted what I
wanted to say, I also know several samples and anecdotes
about bad results after a lens re-polishing and/or
re-coating, I meant those results has to do with the
technician knowledge on this kind of work.
> My 2,8C Xenotar lens was repolished in 1990, it had some
scratches or " cleaning marks", some of them very marked,
it was the family camera after my father left photography
and someone cleaned the lens the wrong way. These marks
bothered me when my father told the camera was mine and I
sent it to Casa Schwarz in Buenos Aires city, they were
Schneider representatives and serviced Schneider lenses.
The technician said me it was necessary to polish the front
element, however they had a limit to re-polish it,
otherwise the optical formula could be modified, he was not
sure all the marks would disappear. They gave me camera and
lens in excellent condition, the lens looked like new,
except for a hardly visible little scratch close to the
front element edge, they couldn't polish it completely
because a deeper polishing could affect the lens
performance, explained me the technician, he also
recommended me to take care of the lens because a second
polishing would affect the optical formula. 30 years after
the polishing, this Xenotar is still an outstanding lens.
> Carlos
>
>
> El lun., 26 de oct. de 2020 20:21, Eric Goldstein
<egoldste@xxxxxxxxx <mailto:egoldste@xxxxxxxxx>> escribió:
>>
>> Hi Carlos-
>>
>> Do you have some evidence or support for this statement
beside anecdotes? My anecdotes come to the opposite
conclusion as yours.
>>
>> Richard - I don’t think you can polish precisely enough
not to change the figure of the glass unless extraordinary
means are deployed such as high precision measurement and
computer aided polishing. We are talking thousands of
dollars in this case...
>>
>> Eric Goldstein
>>
>> On Monday, October 26, 2020, CarlosMFreaza
<cmfreaza@xxxxxxxxx <mailto:cmfreaza@xxxxxxxxx>> wrote:
>>>
>>> Eric
>>> I mentioned Duclós lenses yesterday, however
they work with lenses for movie cameras, they don't t
mention still cameras lenses; Ferdi asked about still
cameras lenses re-coating, anyway it looks like they could
do the work for them.
>>>
>>> Most lenses accept a minimal re-polishing degree
keeping the optical formula , in other words, keeping or
recovering the original quality, the problem for the
technician is to know what is the limit to re- polish a
given lens.
>>> Carlos
>>>
>>>
>>> El lun., 26 de oct. de 2020 19:39, Eric Goldstein
<egoldste@xxxxxxxxx <mailto:egoldste@xxxxxxxxx>> escribió:
>>>>
>>>> We need to spend a little more time with the sentence
Richard included
>>>> here about polishing...
>>>>
>>>> Polishing will change the curve and power of the lens.
I don't think
>>>> most people realize this, and that's not a good story.
I know DP and
>>>> cinematographer who sent lenses away to have a coating
replaced and
>>>> were not happy about what they got back, even from
highly reputable
>>>> outfits.
>>>>
>>>> So the question to ask yourself is will the repair
impede the
>>>> performance more than the loss of coating on one surface?
>>>>
>>>> Here's a well-known, well-established Hollywood
refurbisher that does
>>>> this work in the US
>>>>
>>>>
https://www.ducloslenses.com/pages/glass-polishing-recoating
<https://www.ducloslenses.com/pages/glass-polishing-recoating>
>>>>
>>>>
>>>> Eric Goldstein
>>>>
>>>>
>>>>
>>>> On Mon, Oct 26, 2020 at 6:28 PM `Richard Knoppow
<dickburk@xxxxxxxxxxxxx <mailto:dickburk@xxxxxxxxxxxxx>> wrote:
>>>> >
>>>> > Coating is not trivial. Nor is re-cementing.
I've tried
>>>> > cementing a couple of lenses with poor success. The
cement is
>>>> > available, I used UV curing cement. One of the main
problems is
>>>> > centering. Old lenses were centered by grinding the
edges, edging
>>>> > its called. The old method was to paste the lens on
one tube,
>>>> > rotating in a vertical lathe, and shine a light on
it. The
>>>> > reflection is absolutely stationery when the lens is
exactly
>>>> > centered. The reflection is examined in a telescope
while the
>>>> > lens is pushed from the side. When exactly centered
the lens is
>>>> > clamped by a second tube from the top and the edge
ground exactly
>>>> > concentric and parallel to the optical axis. When
this is done
>>>> > the lenses were cemented and clamped by the edges.
More modern
>>>> > cementing is done by watching the reflections from
the elements
>>>> > after the cement is applied to find the exact
alignment of the
>>>> > elements. When centered they are cured and then the
edge of the
>>>> > entire cemented group is edged. I suppose the edges
could still
>>>> > be used to clamp the lens while it is recemented.
There is
>>>> > problem with lenses where the two elements to be
cemented are not
>>>> > of the same diameter. Those must be cemented first
using the
>>>> > second method and then edged.
>>>> > Modern coating is done by vacuum deposition. The
coating are
>>>> > baked in vacuo. This is the method discovered in the
US for hard
>>>> > coating (although some claim Zeiss discovered it
during the war,
>>>> > I have seen no evidence where the U.S. discovery is well
>>>> > documented). Multiple coating is a complex process
which does
>>>> > exactly as named, two or more coatings are applied
and baked. The
>>>> > coatings must be very precisely controlled for
thikness. This
>>>> > sort of vacuum deposition has been brought to a very
high level
>>>> > of perfection for use in making semi-conductor
electronics.
>>>> > Someone offering re-coating must have at least the
means of
>>>> > single vacuum coating. The early Kodak coatings,
which were never
>>>> > applied to outside surfaces, predated the discovery
of vacuum
>>>> > baking. the coating work but can be removed in the
process of
>>>> > ordinary cleaning.
>>>> > Cementing requires curing. The cure can be heat,
as for
>>>> > Canada Balsam or some synthetic cements, or
ultra-violet light as
>>>> > in some later cements. If the surfaces are not
absolutely clean
>>>> > and precisely matched for surfaces (lost a word
here) the cement
>>>> > may not hold. Canada Balsam is sensitive to heat
and, if not
>>>> > sealed thoroughly at the edges, will slowly
delaminate from
>>>> > absorbed moisture or discolor from oxidation. The
quality of the
>>>> > edge paint seems to be critical. Synthetic cements will
>>>> > delaminate due to incorrect curing. Sometimes the
cement layer
>>>> > developed gaps that look like large bubbles where
the two glass
>>>> > surfaces have pulled apart. Canada Balsam more often
begins to
>>>> > separate at the edges and in very old lenses turns
yellow from
>>>> > oxidation. If the ring of separation is small it
will have little
>>>> > effect on the performance while the bubbles will
destroy the
>>>> > lenses ability to form an image.
>>>> > Polishing is another question. It is possible to
remove a
>>>> > damaged coating but if the actual surface of the
lens must be
>>>> > polished it will change the figure and affect the
performance of
>>>> > the lens. Generally, coatings are much easier to
damage than
>>>> > glass although some types of optical glass are
pretty soft.
>>>> > Be very careful of your lenses. The idea of
cleaning with a
>>>> > resuable microfiber cloth just makes me cringe.
Nothing should be
>>>> > used twice. You can make a one-time-use brush from a
sheet of
>>>> > lens tissue by rolling into a tube, tearing it in
half and
>>>> > folding the feathered edges together to form a
brush. Use that to
>>>> > remove dust. Any particle stuck on a cloth or brush
can scratch
>>>> > the surface. So called "cleaning marks" should never
occur, they
>>>> > are just plain scratches caused by careless cleaning.
>>>> > Real lens cleaning fluid is Ammonium carbonate
while Windex
>>>> > is ammonium hydroxide. The carbonate is much milder
while the
>>>> > hydroxide, at least in theory, can dissolve some
glass. I think
>>>> > the glass is exposed to the cleaner for so short a
time that this
>>>> > is probably not a serious consideration.
>>>> > I don't know where to get real lens tissue any
more but
>>>> > supposedly the makers of Scott and Kleenex are
pretty good at
>>>> > removing abrasives from their products.
>>>> >
>>>> > On 10/26/2020 1:27 PM, F.W. Stutterheim (Redacted
sender ferdi
>>>> > for DMARC) wrote:
>>>> > > Carlos, Jan, John, Volker,
>>>> > >
>>>> > > Thank you!
>>>> > >
>>>> > > Ferdi.
>>>> > >
>>>> > >> Op 26 okt. 2020, om 09:30 heeft Volker Muth
>>>> > >> <volker_muth@xxxxxxx <mailto:volker_muth@xxxxxxx>
<mailto:volker_muth@xxxxxxx ;<mailto:volker_muth@xxxxxxx>>> het
>>>> > >> volgende geschreven:
>>>> > >>
>>>> > >> Hello Ferdi,
>>>> > >>
>>>> > >> just by chance I came across Kanto Cameras in
Japan. They
>>>> > >> offer lens polishing and coating.
>>>> > >> Here’s the link:
>>>> > >>
http://www.kantocamera.com/english/repair/repair.html
<http://www.kantocamera.com/english/repair/repair.html>
>>>> > >>
<http://www.kantocamera.com/english/repair/repair.html
<http://www.kantocamera.com/english/repair/repair.html>>
>>>> > >>
>>>> > >> Best regards,
>>>> > >>
>>>> > >> Volker
>>>> > >>
>>>> > >> Von meinem HAL 9000 gesendet.
>>>> > >>
>>>> > >>> Am 25.10.2020 um 20:33 schrieb F.W. Stutterheim
>>>> > >>> <dmarc-noreply@xxxxxxxxxxxxx
<mailto:dmarc-noreply@xxxxxxxxxxxxx>
>>>> > >>> <mailto:dmarc-noreply@xxxxxxxxxxxxx
<mailto:dmarc-noreply@xxxxxxxxxxxxx>>>:
>>>> > >>>
>>>> > >>> Yes, John van Stelten retired some years ago.
I have not
>>>> > >>> found any other address for having lenses
re-cemented and
>>>> > >>> re-coated. Not that I need one at the moment. Is
such an
>>>> > >>> address known to members of the List?
>>>> > >>>
>>>> > >>> Ferdi.
>>>> > >>>
>>>> > >>>> Op 25 okt. 2020, om 13:25 heeft CarlosMFreaza
>>>> > >>>> <cmfreaza@xxxxxxxxx <mailto:cmfreaza@xxxxxxxxx>
<mailto:cmfreaza@xxxxxxxxx ;<mailto:cmfreaza@xxxxxxxxx>>> het
>>>> > >>>> volgende geschreven:
>>>> > >>>>
>>>> > >>>> PS: I learnt Focal Point no longer exists,
>>>> > >>>
>>>> > >
>>>> >
>>>> > --
>>>> > Richard Knoppow
>>>> > dickburk@xxxxxxxxxxxxx <mailto:dickburk@xxxxxxxxxxxxx>
>>>> > WB6KBL
>>>> >
>>>> > ---
>>>> > Rollei List
>>>> >
>>>> > - Post to rollei_list@xxxxxxxxxxxxx
<mailto:rollei_list@xxxxxxxxxxxxx>
>>>> >
>>>> > - Subscribe at rollei_list-request@xxxxxxxxxxxxx
<mailto:rollei_list-request@xxxxxxxxxxxxx> with 'subscribe'
>>>> > in the subject field OR by logging into
www.freelists.org <//www.freelists.org>
>>>> >
>>>> > - Unsubscribe at rollei_list-request@xxxxxxxxxxxxx
<mailto:rollei_list-request@xxxxxxxxxxxxx> with
>>>> > 'unsubscribe' in the subject field OR by logging
into www.freelists.org <//www.freelists.org>
>>>> >
>>>> > - Online, searchable archives are available at
>>>> > //www.freelists.org/archives/rollei_list
<//www.freelists.org/archives/rollei_list>
>>>> >
>>>> ---
>>>> Rollei List
>>>>
>>>> - Post to rollei_list@xxxxxxxxxxxxx
<mailto:rollei_list@xxxxxxxxxxxxx>
>>>>
>>>> - Subscribe at rollei_list-request@xxxxxxxxxxxxx
<mailto:rollei_list-request@xxxxxxxxxxxxx> with 'subscribe'
>>>> in the subject field OR by logging into
www.freelists.org <//www.freelists.org>
>>>>
>>>> - Unsubscribe at rollei_list-request@xxxxxxxxxxxxx
<mailto:rollei_list-request@xxxxxxxxxxxxx> with
>>>> 'unsubscribe' in the subject field OR by logging into
www.freelists.org <//www.freelists.org>
>>>>
>>>> - Online, searchable archives are available at
>>>> //www.freelists.org/archives/rollei_li
<//www.freelists.org/archives/rollei_li>
---
Rollei List
- Post to rollei_list@xxxxxxxxxxxxx
<mailto:rollei_list@xxxxxxxxxxxxx>
- Subscribe at rollei_list-request@xxxxxxxxxxxxx
<mailto:rollei_list-request@xxxxxxxxxxxxx> with 'subscribe'
in the subject field OR by logging into www.freelists.org
<//www.freelists.org>
- Unsubscribe at rollei_list-request@xxxxxxxxxxxxx
<mailto:rollei_list-request@xxxxxxxxxxxxx> with
'unsubscribe' in the subject field OR by logging into
www.freelists.org <//www.freelists.org>
- Online, searchable archives are available at
//www.freelists.org/archives/rollei_list
<//www.freelists.org/archives/rollei_list>
--
Richard Knoppow
dickburk@xxxxxxxxxxxxx
WB6KBL
---
Rollei List
- Post to rollei_list@xxxxxxxxxxxxx
- Subscribe at rollei_list-request@xxxxxxxxxxxxx with 'subscribe'
in the subject field OR by logging into www.freelists.org
- Unsubscribe at rollei_list-request@xxxxxxxxxxxxx with
'unsubscribe' in the subject field OR by logging into www.freelists.org
- Online, searchable archives are available at
//www.freelists.org/archives/rollei_list
