Green or Purple, lens coating who is newer?

[bressong]

I have several nikon vintage lenses, and as I know nikon developed NIC and SIC  two coating technologies before Z era.

I thought NIC is mixed red/purple and green, and newer SIC definitly is green/yellow from outlooking, for example these AI-S 28/2.8 green/yellow ai-s 50/1.8 longnose green (but to be honest,  I think the green/yellow coating on AIS28/2.8 reflects more light to my eyes)

now I got my 2nd AI 105/2.5 copy, the sn is 75xxxx, coating is green 
but my first Ai 105/2.5 copy, the SN is 86xxxx, the coating is purple and very light green

really strange to me

[bressong]

from low angle, they are all purple

[bressong]

another angle

[bressong]

who can introduce the reason or story behind?

thanks

[jborg]

I did a quick search and found this interesting link which provides some background explanation
https://www.fredmiranda.com/forum/topic/1403368

[Roland Vink]

SIC and NIC are both multi-layer coatings based on the same principal of using thin layers of coating. The coating thickness is 1/4 the wavelength of light, which creates destructive interference to improve transmission and reduce reflections. According to Nikon, SIC is more effective across a wider range of the spectrum, but since it is still a multi-layer coating I don't think it is a dramatic improvement. In most cases you would struggle to see the difference except that some flares are a different colour and in extreme conditions the contrast may be a little better.

In some lenses, such as the AIS 28/2.8 and 28/2, the difference between SIC and NIC coated lenses is very clear, and these are noted on my site (serial number page). On other lenses, such as the AI-S 50/1.4 the NIC and SIC coatings look very similar (maybe only a few surfaces were changed), so I was not able to determine the transition point.

SIC coatings tend to be light orange-yellow-green, while the older NIC coatings are deep purple-red/green/blue colours depending on the angle of viewing. Some NIC coated lenses have other coloured reflections such as orange and yellow, mostly from internal surfaces. NIC coating first appeared on the Nikkor-N 35/1.4 and Nikkor-N 28/2 in 1970. These early multicoated lenses tend to have deep purple-red and blue-green coatings. I imagine that Nikon continually improved their coatings, so the coloured reflections changed over time. It's also worth noting that these coatings are very thin - the thickness is just 1/4 wavelength of light - so any minor variation in thickness would change the colour of the coating. It may be that the difference is colours in the lenses above are just sample variation?

[Erik Lund]

Here is the link to Rolands page with data  Nikon Lens Versions and Serial Nos (photosynthesis.co.nz)

[bressong]

Here is the link to Rolands page with data  Nikon Lens Versions and Serial Nos (photosynthesis.co.nz)

yes, I quite often visit this website, it's great library for nikon fans.

[bressong]

SIC and NIC are both multi-layer coatings based on the same principal of using thin layers of coating. The coating thickness is 1/4 the wavelength of light, which creates destructive interference to improve transmission and reduce reflections. According to Nikon, SIC is more effective across a wider range of the spectrum, but since it is still a multi-layer coating I don't think it is a dramatic improvement. In most cases you would struggle to see the difference except that some flares are a different colour and in extreme conditions the contrast may be a little better.

In some lenses, such as the AIS 28/2.8 and 28/2, the difference between SIC and NIC coated lenses is very clear, and these are noted on my site (serial number page). On other lenses, such as the AI-S 50/1.4 the NIC and SIC coatings look very similar (maybe only a few surfaces were changed), so I was not able to determine the transition point.

SIC coatings tend to be light orange-yellow-green, while the older NIC coatings are deep purple-red/green/blue colours depending on the angle of viewing. Some NIC coated lenses have other coloured reflections such as orange and yellow, mostly from internal surfaces. NIC coating first appeared on the Nikkor-N 35/1.4 and Nikkor-N 28/2 in 1970. These early multicoated lenses tend to have deep purple-red and blue-green coatings. I imagine that Nikon continually improved their coatings, so the coloured reflections changed over time. It's also worth noting that these coatings are very thin - the thickness is just 1/4 wavelength of light - so any minor variation in thickness would change the colour of the coating. It may be that the difference is colours in the lenses above are just sample variation?

I just take out some of my collection.

the AFD 105/2.8 MACRO AFD85/1.8 and ais 28/2.8 looks similar coating yellow/green
AI 105/2.5 75XXXX, ais 50/1.8 pancake ais 50/1.8 longnose looks as another group green

ais200/4 ai 135/3.5 ai 105/2.5 86xxxx purple/blue/red/green, especially ai 135/3.5 is more red

ai 24/2.8 is light blue(yes there is UV, but the real front glass is also light blue), seem less light reflection in my view.

ais 55/2.8 is warm yellow.
ai 50/2 is deep green.

Complicated, Nikkors

[MEPER]

As long as you can see reflected light bounce from the lens surface means loss of light?
But it is quite impressing how much better the modern coatings are today.
If I compare an old L37c Nikon filter with a modern high quality filter there is a big difference in how much light is reflected from the surface.
The same for the new Z-Nikkors lenses compared to older Nikkors.

[pluton]

From the advent of anti-refection coating in the 1930'-1940's, coated lenses from any maker *that I have seen* seem to have colored refections limited to pale amber, purple, and blue.  Starting in the early 1970's, multiple layer coatings introduced such colors such as green, greenish yellow, red, and orange to the lens reflections. Green is the most commonly observed color in Nikon lenses from the MC era.

[Erik Lund]

Here is a very detailed description, see link below for full text:


So, if coated lenses are purple, won’t my photos have a purple tint?

No…. actually, they’ll have a slight yellow-green tint – the extra light that didn’t get reflected passes on through to the film, and there’s a little more of the 550nm yellow-green than there is of the other colors. But it’s not very much – glass only reflects about 4% of light from each surface to begin with, and the coating has some effect at all wavelengths – so there’s maybe a couple of percent of extra green light getting to the film. For most normal photography, this isn’t enough to be noticeable in the pictures. However, some lens makers were concerned about it, and did something to reduce the risk of off-color photos.

Every lens has at least two reflective surfaces, the front and the back. In lenses used for practical photography, there are generally at least six, and there can be 18 or more in complex wide angles or zooms. Each surface presents an opportunity to adjust the color effect of the coating: with, say, six surfaces to coat, the designer can specify six slightly different thicknesses of coating, each corresponding to a different point in the spectrum. If one surface transmits a little extra yellow-green, another a little extra blue-green, a third a little extra orange and so on, the total lens can be balanced to pass a very neutral color of light through to the film. This is why, in some lenses, you will see a number of reflections in different colors: each coating layer is the same Magnesium Fluoride material, each is a single layer, but each is a slightly different thickness to correspond to a different color within the visible spectrum to optimize balance. Not all designers did this – some felt it was better to optimize the entire lens in the center of the spectrum for best overall efficiency, and their lenses tend to have a uniform blue-violet color on every surface.

How Lens Coating Works (tripod.com)


And also here:


Optical Coatings (zen.co.uk)