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Archive 2013 · Watching Aanimal Planet and...
  
 
runamuck
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p.1 #1 · p.1 #1 · Watching Aanimal Planet and...


The guys that build huge aquariums said that acrylic used in their tanks is clearer than glass. Acrylic is 97% clear while glass is only 76% clear. Just what is the clarity of lens glass?


Mar 14, 2013 at 10:34 PM
jcolwell
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p.1 #2 · p.1 #2 · Watching Aanimal Planet and...


I think it depends on what type of glass you're talking about. Maybe they were referring to 'window' glass, or a beer bottle.

OTOH, if you were talking with a sales or marketing person, then nothing is clear, except what they're selling.



Mar 14, 2013 at 11:29 PM
mpmendenhall
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p.1 #3 · p.1 #3 · Watching Aanimal Planet and...


Glass designed for use in optical fibers has attenuation lengths measured in kilometers; over the visible spectrum, a kilometer long optical fiber might lose 50% of the light, and lose only 5% at peak transmission in the infrared. Typical "window glass," however, is often already a murky dark green at only a few inches thick. Everything else usually falls somewhere in-between


Mar 15, 2013 at 01:45 AM
15Bit
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p.1 #4 · p.1 #4 · Watching Aanimal Planet and...


Talking about "glass" is pretty much the same as talking about "plastic" or "steel". It is a big area of materials science and there are a lot of different glasses out there.


Mar 15, 2013 at 06:37 AM
Sarsfield
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p.1 #5 · p.1 #5 · Watching Aanimal Planet and...


My contribution to this thread stolen shamelessly from Wikipedia:

The majority of photographic lenses have the lens elements made from glass although the use of high quality plastics is becoming more common in high quality lenses and has been common in inexpensive cameras for some time. The design of photographic lenses is very demanding as designers push the limits of existing materials to make more versatile, better quality and lighter lenses. As a consequence many exotic glasses have been used in modern lens manufacturing. Caesium[1] and lanthanum[2] glass lenses are now in use because of their high refractive index and very low dispersion properties. It is also likely that a number of other transition element glasses are in use but manufacturers often prefer to keep their material specification secret to retain a commercial or performance edge over their rivals.

The last sentence captures Canikon's philosophy about lenses.



Mar 15, 2013 at 10:28 PM
runamuck
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p.1 #6 · p.1 #6 · Watching Aanimal Planet and...


I had a "killed in a fall" Minolta superzoom P&S. Being curious, I dismantled the lens. I found most of the internal elements were actually plastic rather than glass.


Mar 21, 2013 at 12:47 AM
runamuck
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p.1 #7 · p.1 #7 · Watching Aanimal Planet and...


I just sent an email to the folks at Acrylic Tank Mfg. and asked for clarification. If I get an answer I will let you know.


Mar 21, 2013 at 01:41 AM
 

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jcolwell
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p.1 #8 · p.1 #8 · Watching Aanimal Planet and...


runamuck wrote:


"...asked for clarification.".


"clarity of lens glass"...

I'm just sayin'.



Mar 21, 2013 at 01:47 AM
Imagemaster
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p.1 #9 · p.1 #9 · Watching Aanimal Planet and...


What does it matter? You can't make quality camera lenses out of acrylic.


Mar 21, 2013 at 02:58 AM
jcolwell
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p.1 #10 · p.1 #10 · Watching Aanimal Planet and...


It does matter. I'm interested in what I can do, not what you can't do.


Mar 21, 2013 at 03:01 AM
Imagemaster
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p.1 #11 · p.1 #11 · Watching Aanimal Planet and...


jcolwell wrote:
It does matter. I'm interested in what I can do, not what you can't do.


Well if you can make a 500 f4 lens with acrylic that works as well as my current 500 let me know. I use acrylic beer mugs so I can lift my beer.



Mar 21, 2013 at 04:13 AM
runamuck
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p.1 #12 · p.1 #12 · Watching Aanimal Planet and...


I received a reply from Wayde King of Acrylic Tank Manufacturing. He says that the statement about glass referred to ordinary window glass. Here is the reply.

Is Acrylic clearer than glass? -Making your products and livestock look great and stay healthy

We create product displays, podiums, jewelry cases, and more… -All the way across the board to custom acrylic aquariums that we have created to be placed in professional establishments. As we explore the choice between glass and acrylic, we can’t help but wonder how acrylic materials are so much more clear than glass.


A study of the light that passes through materials has shown that while conventional glass will typically filter out much light including some in the visible spectrum, acrylic resin (Plexiglas) does not. It leaves light untouched for the most part.

Why is this important? If I was using a display case for living plants, or creating a top for a reef aquarium, I would need to be certain that the deep parts of the ultraviolet spectrum are passing through to my plants and animals. Glass may diminish the health of my live stock, and in the case of corals, leave them drab and gloomy.

Light spectrum chart for acrylic vs glassScientists have discovered that while glass will usually start to take much of the visible and invisible light spectrum out, Acrylic / Plexi will not. Acrylic material has the same refraction pattern as water. Glass is all over the place and is simply expensive to engineer it for the spectral output one desires. Please see the chart below to compare Acrylic, Glass, and the light measured on an average (good weather) day. Clearly, we can see how the glass starts to filter out the upper visible spectrum and in other charts can be seen to be unreliable in other parts of the EM spectrum.


It appears one could make lenses of acrylic, but it would pass unwanted parts of the spectrum. runamuck









Mar 21, 2013 at 10:08 PM
crteach
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p.1 #13 · p.1 #13 · Watching Aanimal Planet and...


A lot of microscopes sold to schools these days no longer have glass lenses but use plastic instead.


Mar 27, 2013 at 02:53 AM





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