About lenses and anti-reflective coatings: a call for stepping up the current technology

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Sidney Stratton
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I like your way of thinking. May just make a wire support instead of using different cardboard washers. Then using some white filler material from some old bedding (comforter) to pack around the light.

I see you have different light meters. Are they of equal measurement quality?

Bought the same Uni-T as your 1st pic. Modded the head to turn 180º. Using Bluetooth for sampling and data transmission. Also, want to experiment outside in frigid winter conditions – more like real-life situation.

So far the lumens conversion of my higher output lights (4000 to 6000 lm) concurs with my previous ceiling-bounce tests – although some 5 to 10% less.

Addendum;

The values I get are not absolute but for my own reference. If I publish any test results, I’ll use the Lux values.

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Sidney Stratton wrote:
I like your way of thinking. May just make a wire support instead of using different cardboard washers. Then using some white filler material from some old bedding (comforter) to pack around the light.

I see you have different light meters. Are they of equal measurement quality?

Bought the same Uni-T as your 1st pic. Modded the head to turn 180º. Using Bluetooth for sampling and data transmission. Also, want to experiment outside in frigid winter conditions – more like real-life situation.

So far the lumens conversion of my higher output lights (4000 to 6000 lm) concurs with my previous ceiling-bounce tests – although some 5 to 10% less.

Addendum;

The values I get are not absolute but for my own reference. If I publish any test results, I’ll use the Lux values.


.
LOL, I did the same mod on my Uni-T that you did, also use the Bluetooth too.
The meters were tested in this thread. https://budgetlightforum.com/node/60218
The Uni-t did good for its cost.
The trick is to look at the test results and see the variation at the light your testings frequency 3000K, 4000K etc. and the add or subtract the % from your reading.
.
Example: Say you are checking a 3000K light with your Uni-t, on the chart at “ Kaidomain K2 host led: Cree XM-L2 3000K 90+ CRI “, checked 116lm vs the bench-marked “ MobiLux Class A “ at 138lm. So that will be 16% added to your reading.
.

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I could go on a long talk about my dealings with lumen tubes, even tried to stir some input with no luck. https://budgetlightforum.com/node/72725
Hope this helps. Beer
Sidney Stratton
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Invaluable info!

So to correct for the tint variation, Djozz’ calibrated standard (Mobilux), I can find a correction factor.

Pity he hasn’t any 5000ºK tested light – my standard.

Barkuti
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Agro wrote:
AR coating basics are simple from the optical theory point of view.

So the idea is to introduce an intermediate material with intermediate index.

Light doesn't reflect between air and glass, but first between the air and coating and later again between the coating and glass.

But magnitude of each reflection is much smaller and the total is smaller as well.

Multilayer coating simply adds more layers to the stack, dividing the difference between refractive indices to even smaller parts.

There are no multiple layers of MgF2. MgF2 has always the same index so adding more layers doesn't help. You need to use more material to make a multilayer coating.

Since I am not going to design any multilayer coating I guess this is irrelevant, but since MgF2 is tuned for a given frequency to me is obvious that multiple layers of MgF2 would show some combined behaviour, with each MgF2 layer tuned for a different frequency with a different thickness (the optical thickness of the optical coating must be an odd integer multiple of λ/4 - quoted from Edmund's article).

In any case, I think the goal of this thread was to lure or attract a trustworthy manufacturer of lenses willing to make and sell something to beat the usual lenses for sale, lenses which negatively affect tint (Duv) and CRI. Someone willing to sell internationally for affordable pricing, and of course willing to preserve/maintain the quality of its product (even if periodic reviews are necessary).

Expanded polystyrene lightbox, cool. Thanks for showing Sidney, guess that if I were to build a lightbox I'd choose that way (making every penny Wink count LoL).

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Agro
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Barkuti wrote:

Agro wrote:
AR coating basics are simple from the optical theory point of view.


So the idea is to introduce an intermediate material with intermediate index.


Light doesn’t reflect between air and glass, but first between the air and coating and later again between the coating and glass.


But magnitude of each reflection is much smaller and the total is smaller as well.


Multilayer coating simply adds more layers to the stack, dividing the difference between refractive indices to even smaller parts.



There are no multiple layers of MgF2. MgF2 has always the same index so adding more layers doesn’t help. You need to use more material to make a multilayer coating.


Since I am not going to design any multilayer coating I guess this is irrelevant, but since MgF2 is tuned for a given frequency to me is obvious that multiple layers of MgF2 would show some combined behaviour, with each MgF2 layer tuned for a different frequency with a different thickness (the optical thickness of the optical coating must be an odd integer multiple of λ/4 – quoted from Edmund’s article).


In any case, I think the goal of this thread was to lure or attract a trustworthy manufacturer of lenses willing to make and sell something to beat the usual lenses for sale, lenses which negatively affect tint (Duv) and CRI. Someone willing to sell internationally for affordable pricing, and of course willing to preserve/maintain the quality of its product (even if periodic reviews are necessary).


Expanded polystyrene lightbox, cool. Thanks for showing Sidney, guess that if I were to build a lightbox I’d choose that way (making every penny Wink count LoL).


If you lay multiple layers of the same material, there’s no index change between them. So there’s no reflection and no refraction between the layers. So in effect it ends up working as a single thick layer.

One technique used to build dichroic mirrors is to have 2 materials alternating and playing with layer thickness, each layer pair tuned to some light frequency. Having many layers this way allows ultra-high reflectivity mirrors…but that’s precisely the opposite of what we want here.

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it makes VERY little difference!

(AR coating)

they aren;t cameras!

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