| T O P I C R E V I E W |
| JerryV |
Posted - 25 févr. 2012 : 03:35:11
I just traded up to a Nuvi 2595 but my comment relates to any of the newer models that can be used either in horizontal (landscape) or vertical (portrait) modes. My main problem with my prior 2 models (with landscape only usage) was that the screen blacked out when I used my polarized sunglasses. This is due to a fundamental characteristic of LCD screens, which are all polarized to reduce sunglare. If you rotate any LCD screen while wearing polarized glasses (or keep the screen horizontal while rotating your glasses) there will be 2 positions (180 degrees apart) at which the screen blacks out. This is known in optics as total extinction. This blacking out was always the case in the older "landscape" screens unless you turned your head or the GPS unit 90 degrees (not a smart move when you are driving!). The abilty to orient the newer GPS units either horizontally or vertically allows you the choice of seeing the screen at full brightness. Actually, this could have been solved a long time ago by having the manufacturers orient the screen polarization by 45 degrees, as is done with all LCD computer and TV monitors. If you use polarized glasses, you can see what I mean by rotating the glasses while looking through them at an LCD screen. |
| 15 L A T E S T R E P L I E S (Newest First) |
| JerryV |
Posted - 08 mars 2012 : 15:26:45
I agree. And I think that the situation is more complex than I thought when I first started this thread. The darkening effect (with rotation of the device while wearing polarized glasses) is much more severe with my old 765 than with my new 2595, so Garmin must have done something different with these newer models. But the degree of darkening of the device screen also varies with its angle from the sun and also whether direct sunlight is falling on the screen. |
| ZX14NINJA |
Posted - 08 mars 2012 : 13:14:05
So odd that this topic exists. Yesterday, I made a comment while driving...I was playing with a 3590 and I wear Revo's, which of course suffer from the blacked out screen syndrome...however, the 3590 is completely unaffected by this...no matter which way you look at the device. I noticed that it has some kind of (limited) anti-glare filter installed under the glass...and I guess it does more than just (limited) anti-glare. I had the 3590 and 3790 next to each other...and of course - the 3790 does have the issue when tilted to the right angle.
So I can confirm that the 3590 has some type of depolarizing film on it! |
| geezer |
Posted - 03 mars 2012 : 16:35:09
Thank you AndreyT. Obviously my test was not complete. I did it looking through the filter from front to back. The CP filter has no useful effect in that direction. IE does not cut reflections or darken skies. Looking from back to front it acts the same as linear polarizer. |
| AndreyT |
Posted - 03 mars 2012 : 05:12:07
quote:
Originally posted by guggie
quote:
Originally posted by geezer
There are two types of polarization lenses used in photography. Some digital cameras need Circular polarizers. Others are ok with the standard linear polarizers. I did a test with my 3790 and with the linear Polarizer I could completely block the display with it. The circular polarizer had very little effect on the display no matter which way it was turned.
Bingo. You hit the nail on the head. Circular polarization lenses will not affect the display. ...
That is absolutely and hopelessly incorrect.
The purpose of the polarizing filter (linear or circular) is to filter light based on its polarization plane. That immediately means that if the incoming light is uniformly polarized, that light will be completely blocked by polarizing filter held at certain angle. Again, it doesn't matter whether the filer is linear or circular. Altering this behavior would immediately defeat the very purpose of a polarizing filter.
Both circular and linear polarizers will black out an LCD screen when held at certain angle. In that regard the behavior of circular polarized is absolutely and exactly identical to that of linear polarizer. Those of you who (like me) have a photographic circular polarizer can quickly verify this with an experiment.
The difference between linear and circular polarizer lies in some "post-processing" the circular polarizers applies to already filtered light. That post-processing is required to ensure that the filter does not interfere with metering and auto-focus sensors of SLR cameras. The "front end" of a circular polarizer, i.e. the layer that does the actual filtering, is actually an ordinary linear polarizer. Which is why they behave the same, as far as actual filtering is concerned.
The aforementioned post-processing is defined by the nature of SLR camera sensors. It bears no useful purpose to a human eye, which is why you will not see any polarized sunglasses made with circular polarizers. That simply makes no sense. If you ever see such glasses made, it would simply mean that someone trying to pull off some marketing trick, preying on the scientific ignorance of general public.
Within the context of this discussion the point is moot anyway: circular polarizers will not help you to see the GPS screen (or any other LCD screen) any better.
To alleviate the problem one can try finding polarized sunglasses that have a different (or maybe even adjustable) polarization angle. This can be difficult in situations when you have several screens in your car all with different polarization, thus making it virtually impossible to see everything at once. Ridiculously, my BMW has two native OEM LCD screens with different polarization angles (someone at BMW wasn't thinking clearly).
A more radical solution would be to apply some de-polarizing film over your LCD screens. One can easily find links to such products on BMW forums (because of the problem I mentioned above).
And finally, the reason LCD screens are polarized has noting to do with "reducing glare". Light polarization is the founding principle on which the very idea, the very core functionality of LCD screen is based. |
| JimD |
Posted - 03 mars 2012 : 01:08:04
I think the use of overhead projector slide material is worth a try. The radio display in my model BMW (a 128i) is also not visible with polarized sunglasses (at least some of them, perhaps the linear type). Users with this issue have report great success putting the overhead slide material over the display.
Jim |
| guggie |
Posted - 02 mars 2012 : 18:57:18
quote:
Originally posted by geezer
There are two types of polarization lenses used in photography. Some digital cameras need Circular polarizers. Others are ok with the standard linear polarizers. I did a test with my 3790 and with the linear Polarizer I could completely block the display with it. The circular polarizer had very little effect on the display no matter which way it was turned.
I do not know if any sunglasses use circular polarizers.
You can buy sunglasses made with circular polarization from various companies. They tout compatibility with various 3D video display devices. |
| geezer |
Posted - 02 mars 2012 : 16:15:05
There are two types of polarization lenses used in photography. Some digital cameras need Circular polarizers. Others are ok with the standard linear polarizers. I did a test with my 3790 and with the linear Polarizer I could completely block the display with it. The circular polarizer had very little effect on the display no matter which way it was turned.
I do not know if any sunglasses use circular polarizers. |
| JerryV |
Posted - 02 mars 2012 : 15:37:38
kc1ih - I don't think that this will work. A screen protector will reduce glare (sunlight that is reflected back to you). But this will not help with polarized screens being viewed through polarized lenses. |
| kc1ih |
Posted - 02 mars 2012 : 04:08:45
One possible solution is to use a screen protector, some of them will depolarize the light. |
| danham |
Posted - 25 févr. 2012 : 17:56:44
You prompted me to try a test. I have some very expensive Maui Jim sunglasses with prescription polarized lenses which I use for motorcycling. I fired up my zumo 660 and am sitting in front of my i3 iMac with LCD screen. The computer screen goes black with the glasses in the normal, horizontal position. The zumo does not.
But here's where it gets interesting. The zumo goes black at about 45 degrees from horizontal, then turns bright again at 90 degrees. The computer screen shows some difference at 45 and is bright at 90. Then I powered up my nuvi 760. It behaves like the iMac: not quite black but nearly unreadable at the normal horizontal angle; clear at 90 degrees from horizontal.
-dan |
| JerryV |
Posted - 25 févr. 2012 : 17:31:59
danham - I also use expensive polarized prescription glasses. I don't think it's a question of their design. They all work in the same way. You can test yours by looking through a lens at blue sky. When you rotate the lens you will see the sky darken at 2 positions, 180 degrees apart. (Where this occurs will vary with where the sun is and where in the sky you are looking.) But you will never get close to blackness unless you are also looking at another polarized object, such as a LCD screen. As Boyd suggests, there likely is a big difference in the screen technology that is used. His Nuvi 3790 and Montana 600 may have been designed by the manufacturers to avoid the problems I described with simple LCD screens. |
| danham |
Posted - 25 févr. 2012 : 17:08:05
I've had cheap polarized sunglasses that made LCD screen viewing very difficult, but my present expensive prescription ones don't cause problems. So I'm wondering if there are different ways of designing polarized lenses, with some costing more than others.
I'm not suggesting Jerry owns cheap glasses; I'm speculating about whether high-end prescription glasses somehow manage to avoid the problem.
-dan |
| Boyd |
Posted - 25 févr. 2012 : 16:01:02
That's a very good question. My Nuvi 5000 had exactly the problem you describe (it is an older landscape-only) unit. It became very hard to read with polarized sunglasses - the screen wasn't one of Garmin's brightest models without sunglasses either. I found it incredible that Garmin didn't realize this would be a problem. None of the other Nuvi's I've used have had this problem (205, 650, 1350).
I have a 3790 now and it looks great in both landscape and portrait modes with polaroid sunglasses, but it's a glass capacitive multi-touch screen instead of the resistive screens used in most of Garmin's models (with the exception of the 34xx and 35xx series).
I also have a Montana 600 that looks great in both landscape and portrait mode. But again, this is a very different screen technology not found in any of the nuvi's (transreflective screen that works without the backlight).
Before buying any of the newer dual mode units, I would go into a place like Best Buy and try for myself. I have raised this issue myself before and the usual reaction seems to be "huh?" from most people. Maybe they just don't understand, or maybe there aren't many people with polarized sunglasses? Mine are prescription, so I don't have the option of taking them off or buying another type. |
| JerryV |
Posted - 25 févr. 2012 : 15:47:13
I understand that. This is exclusively a problem for people looking through polarized glasses. But I know that some people have not understood what was happening when the screen blacks out (the same thing happens with the LCD screens of digital cameras). Also, some people have confused this issue with sun glare of the screen, which is an entirely different issue. At any rate, the choice of either landscape or portrait viewing makes a big difference for those of us who use polarized glasses. |
| SergZak |
Posted - 25 févr. 2012 : 04:28:54
I've personally never had a problem with the polarization issue as all my Oakleys are of the non-polarized variety.  |
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