[beholder3]

I read about those coatings over and over, but to me it sounds like pixy dust.

1. protect:
a) from scratches
b) from dust and fingerprints sticking to much
The most expensive special glass types for lens elements often are extremely soft.

2. reduce reflections
a) less flares
b) most important of all: higher contrasts / microcontrasts. Let's not forget the beginner lecture on the fact that "sharpness" and "resolution" is contrast, contrast and contrast and nothing else. The "MTF curves" everyone stares at to judge all this have it in their name: "modulation" - another term related to contrast. MTF is measuring contrast.
c) lets also not forget that light being reflected means less light goes through the glass --> lower transmission --> effectively getting a slower lens

3. affect color
Since the reflections can be different by wavelength, good coatings will have less color cast. I suspect the infamous blueish Sigma "color rendering" is actually a coating problem.


Often in optics around 30% to 50% of the glass value / price is coatings alone.

Coatings become more important especially when light comes in at very different angles. That is for example fast glass with very wide open apertures.

Coatings are anything but pixy dust. They are top level material engineering.

[WorksAsIntended]

) most important of all: higher contrasts / microcontrasts. Let's not forget the beginner lecture on the fact that "sharpness" and "resolution" is contrast, contrast and contrast and nothing else. The "MTF curves" everyone stares at to judge all this have it in their name: "modulation" - another term related to contrast. MTF is measuring contrast.

And this is exactly where a coating cannot do anything more than perfecting the surface of the lense. Reducing reflections (assuming you cannot have a graduant index of refrection inside the coating, which is not possible to be implemented easily) only means changing the angles in which the light hits the lens on a microscopical scale.

---------- Post added 01-17-20 at 03:00 AM ----------

3. affect colorSince the reflections can be different by wavelength, good coatings will have less color cast. I suspect the infamous blueish Sigma "color rendering" is actually a coating problem.

There is only so much you can achieve with the coating there. If the coating is too different in optical behaviour compared to the glass underneath you just get another boundary layer between coating and glass where these effects are produced again.

[Kunzite]

And this is exactly where a coating cannot do anything more than perfecting the surface of the lense.

Like in... polishing the lens' surface into a mirror?
That's not what anti-reflection coatings do: Anti-reflective coating - Wikipedia

[beholder3]

And this is exactly where a coating cannot do anything more than perfecting the surface of the lense. ...

There is only so much you can ...

Yes, let's insist the earth is flat. We don't need to understand what we talk about.

[WorksAsIntended]

Like in... polishing the lens' surface into a mirror?
That's not what anti-reflection coatings do: Anti-reflective coating - Wikipedia

Polishing a glass does not make it a mirror. A mirror is using total reflection which occours from optical dense to optically lens dense surface interaction. In this case a coating would not help to prevent at all (at least if it not also prevents transmission). There of course is a also a mirorrtype that is enabled by polishing, like a cupper plate. This however is due to its electrical behaviour glass does not have.
Polisihng a glass will prevent reflections inside a lens at the angle of the light is steeper this way, which results in lower reflection rate.


The way destructive interference on coatings can be used does not work with camera lenses. This is too dependend on wavelengths.

It can be used (and does in a scientific context) to outcome some specific wavelenght issues. If you for example got purple frining the wavelength indeed is specific enough to get some dempening by interference on it, but you cannot use a thin film diffraction to shut down all kinds of wavelenghts.

---------- Post added 01-17-20 at 04:22 AM ----------

Yes, let's insist the earth is flat. We don't need to understand what we talk about.

Yeah yeah, the flat earth thingy. I don't know about you, but I did my phd in quantum optics and this is the very reason I am very critical on the claims made by manufactureres on what they achieved by coatings. I took the last few hours to read a bit on what they claim to do and most of this wont wort on broad spectrums of wavelengths.

If you use a multi coating structure you can correct aspherical errors yes, but this would mean the coating has to be very specific to every lense which sounds very expensive.
Scattering on the other hand is easily helped by perfecting the surface.

[Reed]

I'm pretty sure Ricoh with HD coatings update also did change used glass formula itself. Still no word officially form Ricoh about it.

[Kunzite]

The way destructive interference on coatings can be used does not work with camera lenses. This is too dependend on wavelengths.

It can be used (and does in a scientific context) to outcome some specific wavelenght issues. If you for example got purple frining the wavelength indeed is specific enough to get some dempening by interference on it, but you cannot use a thin film diffraction to shut down all kinds of wavelenghts.

The current multi-coating treatments for optical lenses do not work equally for "all kinds of wavelengths" (do we include radio here, too? ) You can see the HD response to various wavelengths here:
About HD Coating / Lenses / Products | RICOH IMAGING

Yes, they do generally work by interference, and definitely not by "correcting aspherical errors".

[reh321]

We do not need to know the physics of how Pentax coatings work.
I am not certain that they are generally available.

What we do need to know is that they do work.

[BigMackCam]

We do not need to know the physics of how Pentax coatings work.
I am not certain that they are generally available.

What we do need to know is that they do work.

Absolutely... and we know, from tests, that even though the old SMC coatings were some of the best around for many years, the newer HD coatings are even more effective in dealing with - for example - lens flare. So, whatever the manufacturer's claims may be, and whatever the physics behind them, the coatings work.

[Kunzite]

Until proven otherwise by actual experts, the manufacturer's claims are correct (though perhaps slightly tainted with marketing).

And yes, coatings work, some visibly better than others. The HD coating I'd say is about as good as nano-coatings, which is in line with Ricoh Imaging's claims.
Coating a single optical surface can reduce the reflection (or increase the transmittance) by several percents.

[WorksAsIntended]

The current multi-coating treatments for optical lenses do not work equally for "all kinds of wavelengths" (do we include radio here, too? ) You can see the HD response to various wavelengths here:
About HD Coating / Lenses / Products | RICOH IMAGING

Yes, they do generally work by interference, and definitely not by "correcting aspherical errors".

Those graphs are absolut useless selling stuff.
There are so many undefined boundary conditions that I could produce the same results with hairspray layers.
This is exactly what I mean, there is a lot of claims about those coatings and I am not convinced by many of them. They just not make sence from a scientific standpoint, if you consider the amount of technology they can use for producing the lenses.
I used to work with meta materials, we could even make objects invisble for specific wavelenghts (not all frequencys of the visible spectrum of course). What they claim would be a brakethrough in optics far beoyned that.

---------- Post added 01-17-20 at 11:47 AM ----------

Until proven otherwise by actual experts, the manufacturer's claims are correct (though perhaps slightly tainted with marketing).

And yes, coatings work, some visibly better than others. The HD coating I'd say is about as good as nano-coatings, which is in line with Ricoh Imaging's claims.
Coating a single optical surface can reduce the reflection (or increase the transmittance) by several percents.

The claims are way to unspecific to do any science on them. There is nothing specific at all about the claims. All I said is that the way many seem to think they work, what they dont state themselves, is definitly wrong.
I took part in the development of modern algorithms to simulate such stuff.
Also this is a bold claim to make. I hope I could use this on my products, it is true until prooven differently.

---------- Post added 01-17-20 at 11:48 AM ----------

Btw, do you understand what a "nano coating" does? Exactly the one thing I stated how this could be helping to improve image quality.

[MikeyBugs95]

... I could produce the same results with hairspray layers. ...

I'd pay to see you try.

I guess we'll all just have to agree to disagree although, if someone has a copy of the non-SMC Takumar 50mm f1.4 and one of the many SMC 50 1.4 lenses, a short comparison would be 'helpful' here.

Bottom line, coatings work. End of story. Cut scene.

[reh321]

Those graphs are absolut useless selling stuff.
There are so many undefined boundary conditions that I could produce the same results with hairspray layers.
This is exactly what I mean, there is a lot of claims about those coatings and I am not convinced by many of them. They just not make sence from a scientific standpoint, if you consider the amount of technology they can use for producing the lenses.
I used to work with meta materials, we could even make objects invisble for specific wavelenghts (not all frequencys of the visible spectrum of course). What they claim would be a brakethrough in optics far beoyned that.

The claims are way to unspecific to do any science on them. There is nothing specific at all about the claims. All I said is that the way many seem to think they work, what they dont state themselves, is definitly wrong.
I took part in the development of modern algorithms to simulate such stuff.
Also this is a bold claim to make. I hope I could use this on my products, it is true until prooven differently.

]Btw, do you understand what a "nano coating" does? Exactly the one thing I stated how this could be helping to improve image quality.

You may care how this works but as I already stated in #833, most of us do not know how they work; all we care is that traditional Pentax coatings do work.

[Kunzite]

The claims are way to unspecific to do any science on them. There is nothing specific at all about the claims. All I said is that the way many seem to think they work, what they dont state themselves, is definitly wrong.
I took part in the development of modern algorithms to simulate such stuff.
Also this is a bold claim to make. I hope I could use this on my products, it is true until prooven differently.

---------- Post added 01-17-20 at 11:48 AM ----------

Btw, do you understand what a "nano coating" does? Exactly the one thing I stated how this could be helping to improve image quality.

Sometimes, pretending to know what you're talking about just doesn't work. Let it drop.

[BigMackCam]

Folks - let's keep this friendly and constructive.

Whether we agree or disagree on the manufacturer's claims, one thing that's undeniable is that SMC and HD (and SP) coatings are effective from a user's perspective. They reduce flare, and increase contrast. That much we can all agree on, I hope.

Let's move on from this, eh?

Thanks.