Eyeglasses (1 Viewer)

bh46118 · Nov 16, 2014

What do you use with your binoculars ? Straight glass, polycarbonate, photo gray, special coatings, etc. Which combination of bells and whistles, or lack thereof makes for a good set to be used with binoculars.

Does high quality polycarbonate have any potential for binocular lenses or prisms ?

Bruce

perterra · Nov 16, 2014

bh46118 said:
What do you use with your binoculars ? Straight glass, polycarbonate, photo gray, special coatings, etc. Which combination of bells and whistles, or lack thereof makes for a good set to be used with binoculars.

Does high quality polycarbonate have any potential for binocular lenses or prisms ?

Bruce

I use progressive 1.7 high index aspheric lens for my current glasses, anti scratch/reflective coatings. I usually try to buy rimless though the last two I bought were half rims.

proudpapa56 · Nov 16, 2014

Here in the U.S., glass is becoming a specialty lens. Regular plastic lenses (CR-39) are 1.50 index and polycarbonate lenses are 1.59 index. For stronger prescriptions, that 1.7 index plastic is wonderful for keeping the lens thinner and some lens designs can even be done in 1.74 index. The thinner you make a lens, the more they are prone to glare, so anti-reflective coatings are highly recommended (actually, for any lens). Some of the 1.74 index lenses are only available with A/R coating.
One of the reasons polycarbonate is so popular is because it is very impact resistant on top of being thinner than regular plastic.
Another mid-index impact resistant lens material to consider is Trivex which is "clearer" than polycarbonate.
But for mid to stronger prescriptions, if you don't mind the lenses being just a smidge thicker, and impact resistance is not a concern, 1.60 plastic is another wonderful material. It is considered hi index and with an A/R coating is very easy on the eyes. With a higher Abbe value than 1.66, 1.7 or 1.74 lenses, it is more "transparent" or clearer.
Of all lens materials, polycarbonate has the lowest Abbe value, but its impact resistance makes it a better "all around" lens for most folks.
Regular CR-39 and glass lenses have the highest Abbe values.

P.S. For what it's worth, I wear polycarb lenses because I'm a clutz.

WJC · Nov 17, 2014

Even in ophthalmic dispensing, some white coats don't know what they don't know. As my life drains away, I had to take a job in dispensing.

I had to sit with my mouth shut as I heard my boss tell a customer (with a straight face) that polycarbonate was better than plastic because . . . "Light travels through it faster."

Let me see if I understand this. Light travels this distance around the world 7.45 times a second. So someone is going to note the increase in speed of traveling through a 1/16th-inch medium?

Bill

peatmoss · Nov 17, 2014

My lenses are plastic right now, but I'll be replacing these soon (too many scratches). Eventually, I might consider Lasik so I can use bins with shorter eye relief! 8-P

Tom Bombadil · Nov 17, 2014

proudpapa56 said:
But for mid to stronger prescriptions, if you don't mind the lenses being just a smidge thicker, and impact resistance is not a concern, 1.60 plastic is another wonderful material. It is considered hi index and with an A/R coating is very easy on the eyes. With a higher Abbe value than 1.66, 1.7 or 1.74 lenses, it is more "transparent" or clearer.
Of all lens materials, polycarbonate has the lowest Abbe value, but its impact resistance makes it a better "all around" lens for most folks.
Regular CR-39 and glass lenses have the highest Abbe values.

P.S. For what it's worth, I wear polycarb lenses because I'm a clutz.

In case some readers aren't familiar with the term "Abbe value" this is a measurement of a material's chromatic aberration (CA) and blurring effect. The higher the Abbe value, the clearer the image. Higher end binoculars use ED glass because it has a very high Abbe value and thus produces a clearer image with less CA/color fringing.

A strong perscription eyeglass lens made of polycarbonate will exhibit significant CA. I tried one once and couldn't live with it. I saw color fringing around every bright light and object.

If your prescription is fairly low, like around + or - 2 diopters, then CR-39 will still be pretty thin and it will give you great optics. Better even than the expensive HD eyeglass lenses from Zeiss & others. Those actually have lower ABBE values than standard CR-39 plastic.

If you have strong prescriptions, yielding thicker lenses, then you might want to go with a higher index plastic in order to have a thinner lens. But the higher the index (in general) the lower the ABBE value and thus lower quality optics. And you have the option of those expensive HD lenses, which are the best "thin" lenses.

Kammerdiner · Nov 17, 2014

Tom Bombadil said:
...
A strong perscription eyeglass lens made of polycarbonate will exhibit significant CA. I tried one once and couldn't live with it. I saw color fringing around every bright light and object.

...

Same thing happened to me. I stuck it out for two weeks then just took them back and got plastic. I think my optometrist once told me that only 2-3 people out of 100 are bothered by the CA.

This guy ( http://www.2020mag.com/story/12334/ ) claims CA is not an issue because:

"Most prescriptions will not generate enough aberration to be troublesome in the normal range of vision. The reactions of wearers have been found to be subjective and variable. In static vision, the angle of gaze has to be greater than or equal to 30 degrees (15 mm to one side ), before there is an effect on most wearers. In real life when people perceive something outside of 8 to 10 mm from lens center, they automatically turn their heads. Thus they never leave the central portion of the lens.

All I know is that it drove me a little batty and I've never tried it again.

Mark

Tom Bombadil · Nov 17, 2014

What he says is true for many people. They do use a small portion of their lens and do turn their heads to look at off center objects. However for me, that has never been true. I tend to leave my head more stationary and look off to the edges.

I had thick'ish eyeglass lens, a -6.5 diopter. The CA when using polycarbonate was very significant to me. Way, way worse than the worst $20 binoculars I've ever looked through.

If anyone is interested in a scientific explanation, check this link:
http://www.2020mag.com/ce/TTViewTest.aspx?LessonId=107855

Alexis Powell · Nov 20, 2014

Tom Bombadil said:
What he says is true for many people. They do use a small portion of their lens and do turn their heads to look at off center objects. However for me, that has never been true. I tend to leave my head more stationary and look off to the edges...

I also move my eyes around a lot. That's why I wear aviator style glasses (slightly modified lens shape, to fit a bit closer to the face) and prefer bins with big exit pupils and flat astigmatism free wide fields. For glasses lenses, I use glass--I've no complaints about the quality of the view, and the scratch resistance is very important to me.

--AP

Keith Dickinson · Nov 20, 2014

Over this side of the pond glass spec lenses are fast dying out, less than 1% of our workload is glass lenses, indeed I have never worn glass lenses in my specs at any time. I myself am now using a 1.74 index plastic multifocal spec lens with multi layer anti reflection coating as well as hard coatings. So far over 20 years I have had 1 lens scratch and that was when my specs slipped off my face and the lens hit a metal shelf corner, never had them scratch through using binoculars at all.

perterra · Nov 20, 2014

Glass is verboten in my line of work, I have a pair of fishing glasses that are polarized in glass, but they are so heavy I pretty much havent worn them in years. I need the shatter resistance glass doesnt offer.

WJC · Nov 20, 2014

perterra said:
Glass is verboten in my line of work, I have a pair of fishing glasses that are polarized in glass, but they are so heavy I pretty much havent worn them in years. I need the shatter resistance glass doesnt offer.

I'm using poly but, being a stickler, I get tweaked when I hear someone tell the customer it is more "scratch" resistant than glass. Do I think poly is better? Yep. More impact rresistant? Yep. More scratch resistant? Oh, please! Can't the techs make their points without stretching them? |=o|

Bill

Alexis Powell · Nov 21, 2014

Glass isn't very common over here either, so a few years back I tried to convince myself that I didn't really need it anymore (now that I don't spend as much time around desert sand and salt crystal laden seaside air) and that I could go with plastic with hard coatings. Ugh, what a disaster. After a year, my glasses could have been used as one of those halo or starburst filters for photography. Same for coated glass lenses. I'm back now, for the last three years with plain glass lenses and they are still pristine (and thus much better than even coated glass lenses after they've accumulated some scratches and lots of sleeks) and I am as happy as I was during all the previous many years I used glass. I'm surprised to say that I don't miss multicoatings even slightly. I thought I'd notice a significant, even if modest difference, especially at night, just like I do with coated vs uncoated camera filters, but it just doesn't seem to be important for my glasses.

Apparently, I don't treat my glasses lenses the way I do my cameras and binoculars, which by contrast remain pristine after decades of use. I know I don't clean my glasses as carefully, and I'm always bonking them into hard eyecups and unpadded microscope oculars, camera viewfinders, and the like. I guess it is a wonder they hold up as well as they do. After all, glass does scratch--the glass faces of my wristwatches are heavily scratched, except the one with the fancy sapphire glass crystal. I don't want to change my behavior; luckily, I don't need to, since glass works for me, at least for now with my simple single correction lenses.

--AP

perterra · Nov 21, 2014

WJC said:
I'm using poly but, being a stickler, I get tweaked when I hear someone tell the customer it is more "scratch" resistant than glass. Do I think poly is better? Yep. More impact rresistant? Yep. More scratch resistant? Oh, please! Can't the techs make their points without stretching them? |=o|

Bill

I have probably 5 pair of glasses that get rotated, everything from big shooting glasses, to safety glasses to paper thin postage stamp sized dress wear. Rarely do I have one that gets scratched to a noticeable degree, but I am extremely careful with them when it comes to cleaning, when a perscrip cost $450 or so I am not one to abuse them. The ones I have had get scratched, well they do scratch pretty easy so they get rinsed well before wiping.

I did have a pair that got hit with an over spray of epoxy paint at a customer 2 years ago. The lens were pretty much history.

etudiant · Nov 21, 2014

Alexis Powell said:
Glass isn't very common over here either... After all, glass does scratch--the glass faces of my wristwatches are heavily scratched, except the one with the fancy sapphire glass crystal. --AP

Unfortunately the failure of Apple's plan to put sapphire glass on their new Iphone 6 also puts paid to any near term dreams of sapphire glass for glasses. It would be great to have really durable material for glasses, because the plastic lenses are anything but. Even babied, cleaned with only soap and water, patted dry, never any fabric wiping, my glasses too gradually develop a haze of fine scratches. Still, the lenses are a lot thinner and lighter than their glass equivalents would be, so I'm content.

Tom Bombadil · Nov 21, 2014

Alexis Powell said:
I also move my eyes around a lot. That's why I wear aviator style glasses (slightly modified lens shape, to fit a bit closer to the face) and prefer bins with big exit pupils and flat astigmatism free wide fields. For glasses lenses, I use glass--I've no complaints about the quality of the view, and the scratch resistance is very important to me.

--AP

I primarily used crown glass for years for my eyeglasses. Even though my prescription was -6.5 diopters and thus quite heavy with glass. The optics were so much better than polycarbonate and high index plastic. I tried a polycarb and a 1.6 index plastic along the way but couldn't deal with the fuzzy off-center optics or CA of either.

Eventually I had to under cataract surgery and my prescription dropped to under -1.0 diopter. I happily went back to CR-39 and have loved the results of having both great optics and light weight. My current prescription is too thin for glass, as it would break so easily.

Pinewood · Nov 24, 2014

Hello,

I wear high index plastic, progressive eyeglasses with an anti-glare coating. Progressives definitely make the edges fuzzy.
I cannot understand why this image is on its side. If you click on it, the image should right itself

Happy bird watching,
Arthur Pinewood :hi:

perterra · Nov 24, 2014

Pinewood said:
Hello,

I wear high index plastic, progressive eyeglasses with an anti-glare coating. Progressives definitely make the edges fuzzy.
I cannot understand why this image is on its side. If you click on it, the image should right itself

Happy bird watching,
Arthur Pinewood :hi:

Nope, still sideways.

Progressives can pretty much nullify this edge to edge sharpness I hear about. I have spent as much as $800 and as little as $200 on my glasses. Didnt seem to make much difference in anything other than weight.

Pinewood · Nov 24, 2014

perterra said:
Nope, still sideways.

Hello,

It goes upright when I click on it.

Happy bird watching,
Arthur :hi:

elkcub · Nov 25, 2014

Try putting your beret on to the right and see what happens.

Ed

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