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Torch down the objective...colours?

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#1 Steve Napier

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Posted 04 August 2005 - 08:48 AM

Hello.
I pointed a 4 cell maglite down my Zeiss 7x42 FLs last night and the amount of different colours on the reflections was amazing, red,brown,green,purple,blue,yellow and a few others too,is this due to the flouride element or the coatings or a combination of the two?
I tried the same process in my 8x30 deltrinems but only saw purple and nowhere as near many reflections.
Thankyou
Steve.

#2 Erik D

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Posted 04 August 2005 - 09:24 AM

Hello Steve,

Can't answer your question about MC, FMC, BroadBand FMC, etc. But Welcome back to the CN Bino Forum! Look forward to more posts from you.....

ERik D

#3 Guest_**DONOTDELETE**_*

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Posted 04 August 2005 - 09:31 AM

I have never used bins with fluoride glass. The coatings are to improve the light through put so reflections should be minimal. For instance with both of my Oberwerk bins, I see a faint green hue and nothing else. Maybe there is something a-miss with your coatings or perhaps the coatings, in combination with fluoride, is causing a spectrum of colors to be reflected. Either way, what you are seeing doesn't seem good.

#4 Joad

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Posted 04 August 2005 - 10:12 AM

Glad to see you back, Steve.

Now, to your problem: you're sure you weren't looking into a kaleidescope? :whistle:

#5 btschumy

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Posted 04 August 2005 - 10:59 AM

Possibly the different colors are coming from different layers in the Zeiss advanced coatings.

Are you shining the light on-axis? Reflections from off-axis light may not tell you too much about the performance of your binocular. Remember, you are only capturing light from the central 6º-8º. As long as off-axis light isn't scattered into your binocular, you don't care where it reflects to.

#6 Henry Link

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Posted 04 August 2005 - 12:52 PM

Steve,

I don't think there is anything to worry about. I see the same thing in my FL's and other complex multi-coated optics. I've seen a few explanations offered such as: Different multi-coating materials are matched to the refractive index of the element being coated, or the reflection color results from the coating material used for the top layer in the multi-coating of a particular element. Your Deltrintem sounds like it is coated with MgF, one layer of one material on every element.

You would see more reflections in the FL. From the front surface of the objective to the front surface of the prism there are 7 glass to air surfaces in the FL, 3 in the Deltrintem.

#7 Guest_**DONOTDELETE**_*

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Posted 04 August 2005 - 02:56 PM

I think Bill's note is a good one. Definitely. If the incident angle is oblique then that certainly would affect the reflection. To what degree I am not sure of.

I don't think there is anything to worry about either, but some of the general explanations that you heard of Henry sound suspect to me or perhaps they don't completely explain the phenomenon. For instance, for multiple coatings one is not only concerned with the glass element, but the coatings that lie underneath as well.

#8 Steve Napier

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Posted 05 August 2005 - 09:21 AM

Hi and thanks for your replies and your welcome back.
I think that Henry might have the answer with the many air to glass surfaces and the exotic coatings.
I was shinning the torch directly down the objective full on.
I was not worried when I made this post I was merely expressing my amazement at all the different colours and shades,it really does look fantastic.
As for the 7x42 FLs,they are stunning terrestrial binoculars with absolutely know false colour what so ever,they are the best piece of equipment I have bought so far and I urge people to try to test a pair out.
Im sure I would recieve exactly the same picture as Kenny Jones "Perfect Portholes" but,I think the massive 8.6 degree field is too large to give this impression.
Thankyou
Steve.

#9 Guest_**DONOTDELETE**_*

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Posted 05 August 2005 - 09:32 AM

Your description Steve reminded me of what a thin sheen of oil or liquid soap can look like at the right angle.

Good to hear the bins are fine...which is MOST important.

#10 Steve Napier

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Posted 05 August 2005 - 09:47 AM

Hi Night Watch,actually you are spot on as to the type of colours I was seeing,I can assure you though the bottle of Fairy Liquid goes nowhere near those glasses.
Those skies behind you on your photo look perfect Astronomy skies,you lucky lad.
Thankyou
Steve.

#11 Guest_**DONOTDELETE**_*

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Posted 05 August 2005 - 10:19 AM

Ah, yes. Thanks Steve. That picture was taken in a remote area of New Hampshire where my inlaws live. The darkest spot I have ever been to and in the winter....it's amazing.

#12 Joad

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Posted 05 August 2005 - 03:18 PM

Ah, yes. Thanks Steve. That picture was taken in a remote area of New Hampshire where my inlaws live. The darkest spot I have ever been to and in the winter....it's amazing.


Well, that explains that, NW. Your avatar's background sure never looked like the Boston I remember! (I lived in the Boston area for seven and a half years).

#13 Guest_**DONOTDELETE**_*

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Posted 05 August 2005 - 04:14 PM

No kidding. Those two worlds, rural NH and Boston, are nothing alike. The light pollution in the summer where I live is terrible so every chance I have when I go up north I am always packing my bins.


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