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Saintsman
2nd Mar 2015, 20:52
I'm in the market for a new pair of shades.

I was at the optician recently and they recommended polarised lenses, but I seem to remember they 'affect' the windscreen when driving.

What's best, polarised, tinted or doesn't it really matter?

Dash8driver1312
2nd Mar 2015, 21:03
The largest mirrored aviators that money can buy.

Shaggy Sheep Driver
2nd Mar 2015, 21:55
Ray-Ban aviators. That's it!

Polarised for the beach, non-polarised for the cockpit.

onemac
2nd Mar 2015, 21:56
I use polaroid prescription sunglasses for driving and apart from seeing a slight pattern occasionally they are fine.

Al

G-CPTN
2nd Mar 2015, 22:08
Polarised sunglasses were worse when car windscreens were 'zone-toughened'.
I believe that most are now laminated.

Captain Dart
2nd Mar 2015, 22:21
I fly from a busy gliding airfield. I have been told that polarised sunnies can make it easier to spot white fibreglass gliders. Thoughts/experiences??

Shaggy Sheep Driver
2nd Mar 2015, 22:25
Can anyone recommend somewhere to buy Ray Bans at a good price?

Romeo Hotel
2nd Mar 2015, 22:31
I have found that polarised lenses give great definition in cloudy skies, try some and stare at a cumulus. I think you'll be surprised how good they are. That being said, I use non polarised for flying to be able to see the nav display!

Have a trip to sunglass hut and try lots of them, of course aviators are mandatory as is the leather jacket!

Saintsman
2nd Mar 2015, 22:55
Can anyone recommend somewhere to buy Ray Bans at a good price?

If you have a local Costco, they have some good deals.

Fox3WheresMyBanana
2nd Mar 2015, 22:59
A set of polarised is very useful when on the water (e.g. avoiding coral whilst sailing yachts in the Tropics)

superq7
2nd Mar 2015, 23:25
Shaggy Sheep, try Sunglass Hut I got a good discount when I bought some Ray Bans from them recently, this was at the Mall at Cribbs Causeway, Stu.

PlanetEarth
2nd Mar 2015, 23:38
I've used Ray-Ban polarized sunglasses in and out of the cockpit for many years now, and I have yet to run into any kind of problems with them in regards to screens.
Only way to make the screens fade is if I tilt my head 90 degrees.

Metro man
3rd Mar 2015, 00:47
I like Polarised glasses where glare is a problem, such as being on the water. Unfortunately, now that I need progressive glasses for normal vision, my sunglasses choices are limited as the lenses need to be reasonably flat.

I've gone with photo chromatic, progressing glasses which saves me from having to swap around, but isn't the cheapest option.

G0ULI
3rd Mar 2015, 01:02
Zeiss make specific lenses for aviation, quite a dark green tint to look at, blocks all UV light but they don't distort colour vision for some reason. I have used a prescription pair for over 20 years for distance vision. The coatings also allow you to see about a third further into fog than with the naked eye and reveal a wealth of detail when looking at clouds. Recommended but extremely expensive! Worth the money if you need prescription lenses for flying.

Pinky the pilot
3rd Mar 2015, 01:10
Zeiss make specific lenses for aviation,

GOULI; Don't happen to know the name/type of those lenses do you?

Checkboard
3rd Mar 2015, 01:13
If you fly, do NOT buy polarised sunglasses. LCD screens emit polarised light (it's how they work), so polarised sunglasses may stop you seeing the screens.

There are several reasons to wear sunglasses. It is generally accepted that glare is harmful to the eye and that protection from glare is therefore therapeutic, even though studies show that only 22% of the population reacts adversely to glare. For these people the pupils are nearly pinpoints under such exposure. Diminished retinal luminescence cause measurable visual decrements and sunglasses will improve this visual acuity problem by counteracting the amount of available light. Conversely another 11% are at the opposite end of the sensitivity spectrum, these people actually have improved acuity under high glare conditions and seem to have no need for sunglasses.

It is not necessary to wear lenses inside the aircraft to protect a pilot from the injurious part of the UV spectrum, because canopy or cockpit windows will also block UV-B. (Acrylics, however, will not block UV effects and Ultra light or open-cockpit flyers will need sunnies.) UV-C is absorbed by the atmospheric ozone and is not supposed to reach the earth. Infrared rays (as in a heated cockpit) are not known to be a eye hazard.

Sunglasses are therefore essential for most pilots in order to cope with glare. The most important consideration for sunglasses is that they reduce glare without affecting vision. Lenses should not be too dark and the standards given for pilots is that they transmit at least 15 per cent of incident light. The tint must be "Neutral density" (ND) which means that it doesn't affect colour perception. The recommended tint for aviation sunglasses is therefore ND15. (This is the US military specification standard for aviators sunglasses and tinted visors, and may have its scientific origins in a 'best guess scenario' more than fifty years ago.) Only sunglasses that conform to the Australian standards should be worn . Those marked "specific purpose sunglasses" are recommended.

Pilots who wear prescription sunglasses may either wear clip-on lenses or they can get their prescription sunglasses made with ND15 lenses. Clip-ons have the advantage of being easy to remove when there is a quick change from light to dark conditions.

If you chose to have your prescription lens made with a tint then it is essential to have another pair of untinted lenses for night and low glare flying. Pilots who wear look-overs are advised to use bifocals instead and then wear clip-ons.

There are two main materials, crown glass and a plastic known as CR39. A very tough poly carbonate lens material is also available. All three lens materials are acceptable. CR39 and polycarbonate have these advantages :

highly impact resistant;
light weight; and
low thermal conductivity and thus less liable to fogging.


CR39 is more vulnerable to surface damage than glass and CR39 lenses must be carefully protected from scratching. CR39 can be obtained with an abrasion-resistant coating to reduce its susceptibility to surface damage.

Polaroid lenses should be left in your boat. (Everybody has one right :))

During World War Two, most of the patents for the Cathode Ray Tube (CRT) display system were held by US companies, like RCA. The military application at the time was for radar displays.

The British wanted a display technology under different (i.e. their own) control, and funded development, which eventually lead to the Liquid Crystal Display (LCD).

How it works: Light travels as two waves, an electrical wave, supported by a magnetic wave at 90, and as such has an orientation. A polarised filter only allows one orientation of the wave to be transmitted. If you set up one piece of vertically polarised glass, then only vertically polarised light is transmitted, place a second piece of horizontally polarised glass in line, and no light will be able to pass through both sheets of glass.

A liquid crystal is a substance that exists as a liquid, but has long electrically charged, molecules that tend to line up with each other (due to the electrical charge on the molecule), causing a crystalline effect. Crystals can redirect light.

So if you fill the space between the two sheets of polarised glass with a liquid crystal, then apply an electric charge between them, you can line up the crystals in such a way as to rotate the polarised light by 90. The places between the glass with the electric charge will transmit light through the two polarised filters, the places without charge will not. All of the light that is transmitted leaves the display polarised. That is how an LCD works.

Now if you put another polarised filter in front of your eyes - i.e. polarised sunnies, the sunnies will block the light leaving the display if the sunnies' filter doesn't match the polarisation of the display.

Polarised sunnies' chief attribute is that they will completely eliminate glare coming from a flat surface that is of an angle of approximately 53% (That's most reflected light from a water or snow surface.). They are designed mainly to cut glare from water. A pilot wearing Polarised lenses sees the world as constantly changing, according to his (or her) angle of bank, as the angle of the glare is altered. They aren't suitable for aviation.

Liquid crystal displays work by electrically controlling filtered polarised light, so any LCD will appear blank with polarised lenses on, and looking through a polarised window can result in no view at all!

Lens colors are seen in different ways:

Green or grey are said to give the least color distortion, and are available in combination.
Yellow has the capability of filtering reflected short-wave blue which is found in air contaminants such as fog, haze, smoke or smog. In certain conditions therefore yellow "blue blockers" can improve visual acuity, but not because they protect from glare. Yellow lenses that cut out more than 30% of ambient light can affect color perception and military pilots complain that depth perception is altered.
Brown, if it is not too dark, will enhance contrast as well as doing a modicum of blue-blocking.
Rose also increases contrast and blue-blocking offering a niche in car use.


In summary, aviators' sunglasses should:

be glass or polycarbonate;
transmit not less than 25% of available light;
not distort colors, distances or shapes;
nullify the blurring effect of short-wave reflected blue;
have their adverse effect on visual acuity well understood; and
not be worn under conditions of diminished light.


As an aside, I bought a pair of glass Serengettis with a brown tint for nearly $AUD300. I didn't like the weight of the glass lens at all, and the brown tint, while it was good for glare, made the green information on EFIS a little hard to see when I transistioned to EFIS. In addition the inside of the lens was highly relfective, so as I was sitting in shadow (in the cockpit) looking out at a bright field (like a cloud deck from above) they gave me a perfect image of my eyes looking back at me (reflected from the inside of the lens). That was difficult to ignore. I now fly with a pair of $AUD15 plastic sunnies I bought from a Chemist and I am much happier with them.

In Australia pilots may claim one pair of sunnies per year at tax time. :)

sources:
-CAA (Australia) Aviation Safety Digest (ASD) 150 (1991)
-ASD 136 (Autumn 1998)
-ASD 133
-CASA's Flight Safety Australia (Sept. 1997)

Copies of all of these articles are available for free if you contact (Australia'a CASA or BASI)

G0ULI
3rd Mar 2015, 01:50
Pinky,

I bought the glasses having read a review on the best prescription lenses for aviation in Pilot magazine or similar publication. This was probably back in the mid 1980's. The lens coatings block specific frequencies of light, rather like a high end camera filter, which makes them rather pricey. I told my optician what I wanted and he found the lenses and fitted them to the frames I selected. Aviator style, naturally.:)

A look at the Zeiss website shows they have a lens called the Zeiss Skylet which probably corresponds to what I bought all those years ago. They really do enhance contrast and are my go to glasses for flying and summer driving.

I am fortunate that my eyesight prescription is very low and rather unusually hasn't changed over the years. I am certified to fly and drive without glasses, but it is maginal nowdays, so better safe than sorry.

ExSp33db1rd
3rd Mar 2015, 03:19
I use Solar Shield wrap-arounds, Polarised but it doesn't seem to affect the windscreen, but does make it difficult to see the onboard computer data, and probably would a TomTom GPS navigation system - but I don't need that, my map tells me all I need - and I don't need to know my average speed over the last 45.5 minutes that I have been driving, or the fuel consumption, or the distance to go to empty tanks.

Used to be useful to fit over the bi-focals, but then I discovered little plastic half moon enlarging lenses to stick inside the wrap-arounds, so don't need the extra bi-focals now when driving.

Don't fly in them, the sidepieces are too thick to fit under a headset, and the chunky side pieces obscure too much of the sky, where The Hun in the Sun would appear from ( or some innocent Cessna student these days ) for that I have a pair of Ray-Ban look-a-likes bought from some stall in PatPong ( Bangkok ) many, many, years ago.

Who cares about designer labels, try some on and see if you like them.

Preferably prefer Shades of Grey ( only 3 or 4, 50 would be too many ) not in favour of green or orange lenses.

robtheblade
3rd Mar 2015, 04:02
If it is polarised lenses you need there is nothing to match Costa Del Mar. Top end of expensive but they come with a lifetime guarantee. I bought mine after noticing all the Keys fishing guides had them. After ten years the arms started to wear a little so I returned them and got a new pair by return post. My Ray Ban Aviators come a distant second.

Pinky the pilot
3rd Mar 2015, 04:43
GOULI; Thanks.:ok:

Checkboard; Likewise. Most informative.:ok:

Solid Rust Twotter
3rd Mar 2015, 06:14
Don't wear sun glasses. Don't need 'em.

Apparently a company called Randolph make some good ones for flying.

Heliport
3rd Mar 2015, 07:19
Everything you need to know (and more): http://www.pprune.org/rotorheads/220987-pilots-sunglasses-9.html

Piper.Classique
3rd Mar 2015, 08:04
I wear contact lenses, and need distance and reading correction. As the CAA don't want me to fly in multifocal contacts, I use single vision contacts, and my optician makes my sunglasses as varifocals with the top half no correction and a small reading area at the bottom. Much nicer than bifocals, and I can choose my color. (Dark brown works for me)
If it's a bit gloomy outside I use a pair of half moon glasses if I need to see a map more clearly.
This works nicely for driving, as well.

criticalmass
3rd Mar 2015, 08:27
For decades, both at sea and in the air, I have used Zeiss Dark Umbral lenses set in frames of my choosing. My father before me did the same.

Very expensive, and the glass is rather soft, but for contrast in the sky (clouds etc) they are hard to beat. Not a polarised lens at all, so no problems with modern flight displays.

Zeiss Dark Umbral. Use no other!