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Helios coating question
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PostPosted: Tue Feb 02, 2016 5:29 am    Post subject: Helios coating question Reply with quote

As a first time Helios user I noticed its coating is different from my Japanese and Germany lenses. Is this circular rainbow rings like coating common among Helios? Thanks...

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PostPosted: Tue Feb 02, 2016 5:54 am    Post subject: Reply with quote

all russian lens aren't produce in same factory and also helios-81 is completely different species compare to helios 44 series. i have 3 helios-81 and 2of them has this kinda effect and i think it is not just the coating and the glass it self has some kinda sub-standard production line because it also has so many tiny bubble inside the elements.


PostPosted: Tue Feb 02, 2016 6:53 am    Post subject: Reply with quote

Thanks for your insights and by chance I found it could happen to a leica:

http://photo.net/leica-rangefinders-forum/00aMuk


PostPosted: Tue Feb 02, 2016 8:43 am    Post subject: Reply with quote

Raxar wrote:
all russian lens aren't produce in same factory and also helios-81 is completely different species compare to helios 44 series. i have 3 helios-81 and 2of them has this kinda effect and i think it is not just the coating and the glass it self has some kinda sub-standard production line because it also has so many tiny bubble inside the elements.


Helios-81 is an evolution of Helios-65, with lanthanium glasses. Maybe that's why?


PostPosted: Tue Feb 02, 2016 9:14 am    Post subject: Reply with quote

BurstMox wrote:
Raxar wrote:
all russian lens aren't produce in same factory and also helios-81 is completely different species compare to helios 44 series. i have 3 helios-81 and 2of them has this kinda effect and i think it is not just the coating and the glass it self has some kinda sub-standard production line because it also has so many tiny bubble inside the elements.


Helios-81 is an evolution of Helios-65, with lanthanium glasses. Maybe that's why?


obviously the coating has some issue (uneven coating thickness or something like that) and you seen that in nature (thin-film effect) so quality control is the main reason but i'm not sure using rare-earth glass make things worse or better. as i said the QC in this lens are horrible! they only 20-25 yo but most of them has aperture issue and they and so many bubbles in them and some of them the coating of last element wore out easily!


PostPosted: Tue Feb 02, 2016 10:21 am    Post subject: Reply with quote

Raxar wrote:
BurstMox wrote:
Raxar wrote:
all russian lens aren't produce in same factory and also helios-81 is completely different species compare to helios 44 series. i have 3 helios-81 and 2of them has this kinda effect and i think it is not just the coating and the glass it self has some kinda sub-standard production line because it also has so many tiny bubble inside the elements.


Helios-81 is an evolution of Helios-65, with lanthanium glasses. Maybe that's why?


obviously the coating has some issue (uneven coating thickness or something like that) and you seen that in nature (thin-film effect) so quality control is the main reason but i'm not sure using rare-earth glass make things worse or better. as i said the QC in this lens are horrible! they only 20-25 yo but most of them has aperture issue and they and so many bubbles in them and some of them the coating of last element wore out easily!


Use of lanthanum glass increase resolution by limiting the diffractions.
Construction quality is usual problem with arsenal factory lenses.
But bubble is known to not be a problem at all. Often said that it's even sign of good glass quality. We often find them in early 50's lenses. According to factory recommandations, it is also not a problem for IQ.


PostPosted: Tue Feb 02, 2016 11:13 am    Post subject: Reply with quote

Umm interesting to learn that all. By luck I see similar rainbows again - on the resulting images:

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Again I don't know if it has anything to do with the rainbows on the glass but it looks fun.


PostPosted: Tue Feb 02, 2016 11:57 am    Post subject: Reply with quote

It's not oil?


PostPosted: Tue Feb 02, 2016 12:55 pm    Post subject: Reply with quote

It looks dirty inside the lens. A good cleaning may help.


PostPosted: Tue Feb 02, 2016 1:44 pm    Post subject: Reply with quote

I guess someone has messed up something in the manufacture of the lens, and coated the lens with a too thick coating layer. Theoretically, the thickness of a single layer coating should be λ/4, which is approximately 0.00013 mm for green light. However, a thickness of 5λ/4, 9λ/4, 13λ/4, etc., also cancels the reflection for normal incidence, but strange rainbow effects may appear for oblique incidence, exactly what you see in the picture. It's just like the rainbow effect you see in a film of oil on water.


PostPosted: Tue Feb 02, 2016 3:27 pm    Post subject: Reply with quote

It is enlightening Gerald , and I can only add that from the shots of the more evenly lit scenes the lens appears to be very sharp at centre. I like your quote. Smile

Calvin good to see we're both in HK!


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