Lens Filters

[laknox]

Does anyone make lens filters for dashcams? I'm thinking polarizing to help cut glare. Just curious.

Lyle

 

[kamkar]

The individual brands have CPL filters for their models, some time a filter cover more models, other times every model have its own filter due to FOV change in lens.

Really / IMO CPL filter should come with the cameras CUZ 99 % of people are going to need one.
A #2 option are to put a flat black dashmat over your dashboard i have that too, though it is a DIY dashmat made out of some dark felt as no one make dashmats to my silly little Japanese 5 door mini hatch.

 

[laknox]

The individual brands have CPL filters for their models, some time a filter cover more models, other times every model have its own filter due to FOV change in lens.

Really / IMO CPL filter should come with the cameras CUZ 99 % of people are going to need one.
A #2 option are to put a flat black dashmat over your dashboard i have that too, though it is a DIY dashmat made out of some dark felt as no one make dashmats to my silly little Japanese 5 door mini hatch.

Thanks. I have a Thinkware cam, so I'll check with them to see what they have. I'm not talking about dash glare, though; more like sun glare or headlight glare at night.

Lyle

 

[Dashmellow]

In the days before polarizers were made available for dash cams by camera manufacturers many DCT members made their own and some of us still do that for cams that don't have them available or for specialty projects. You'll find many interesting examples shown by members in the DIY sub-forum and elsewhere on DCT going back to the early days of this web site. There's no reason you can't do the same, however there are really no practical optical filters available that will ameliorate headlight glare at night that won't also compromise the low light performance of your dash cam. As for sunlight glare, other than reflections from your dashboard, a CPL is still your best option. A low factor ND (neutral density) filter might help but that would increase motion blur. (a CPL, which also cuts out some of the light entering the lens has some of the same light blocking qualities of an ND filter which is partly why it would help with sunlight glare along with polarization.)

 

[kamkar]

When i got my Lukas LK-7500 camera a decade ago, well it can with a UV filter for some reason.
I never used it though, no idea why it would be there.

Flaring / haloing lights at night ( car headlights & street lights ), i dont really think you can get out off without loosing bit on must have things like a fast enough exposure rate.
I general we have always just gone, "make sure your glass are clean properly inside and out" + any possible filters ( CPL ) that might be there.

I think there have also been som murmurs on the forum of CPL filters doing this as a result of low quality.

Personally i do not care much as i only expect the big picture of a dashcam and for sure nothing cinematic related, so little detail i will of course take, but if its not there i am not surprised.

 

[Dashmellow]

These days UV filters are primarily used to protect expensive lenses from dust and damage. Today's digital sensors are nowhere near as sensitive to UV light as film so they are no longer necessary. They were primarily used to reduce haze in film based color photography. Some UV filters have the potential to decrease image quality by increasing lens flare, and can add a slight color tint. They can also reduce contrast in some circumstances. Very high quality multi-coated UV filters can reduce flare and will not introduce color tints but filters like this are really not available for dash cams nor are they affordable or practical.

 

[laknox]

Thanks for all the info, people. I know that I always wear polarized sun glasses and, being in Arizona, they're just about required for driving in the summer. I see so many videos where the sun is a huge factor, that it completely washed out the view. I know that that is greatly reduced by polarized glasses. I know that my cam has adjustable exposure for both night and day, so I could increase low-light sensitivity and see how it works with the filter in place. I've only had my cams for about 3 months, so am still learning. I don't do a lot of driving, these days, so I'm not getting a lot worth saving. I =have= had a couple incidents, though, that, had they gone sideways, the cam likely would have saved me. One thing that's =real= pet peeve, is speeders in school zones. I live about a quarter mile from an elementary school and about a half mile from a second elementary and jr. high on one campus. The second zone is on a major surface street (2 lanes each way plus a turn lane) and it's marked with flashing lights at 35 mph. I've had people pass me at 55-60. Had I had my dash cam back then, I'd've captured the video and given it to a cop buddy. I know they can't do anything after the fact, but they =can= go knock on the offender's door and give them a "friendly" warning.

Lyle

 

[Dashmellow]

I know that I always wear polarized sun glasses and, being in Arizona, they're just about required for driving in the summer. I see so many videos where the sun is a huge factor, that it completely washed out the view. I know that that is greatly reduced by polarized glasses.

Keep in mind that polarized (as well as unpolarized) sunglasses are heavily tinted (and UV filtered as well) to block out sunlight compared with polarizing filters on dash cams that are only slightly tinted.

 

[laknox]

Keep in mind that polarized (as well as unpolarized) sunglasses are heavily tinted (and UV filtered as well) to block out sunlight compared with polarizing filters on dash cams that are only slightly tinted.

I've seen completely =untinted= polarizing lenses, so not all are tinted. Thinkware does sell a CPL that is virtually clear. I think I'll drop the $20 for one and see how it works.

FWIW, in h.s., many years ago, we worked with polarizing lenses in physics. One of the cool things was having 2 lenses that could be rotated against each other. They'd go from completely clear to black, when the polarizing filters were perpindicular to each other.

Lyle

 

[Dashmellow]

I've never seen untinted polarized sunglasses but I doubt you would be too happy with such glasses driving around in bright Arizona sunshine, which was what you were talking about when comparing polarized sunglasses to camera CPLs.

There is no such thing as a "virtually clear" polarizing lens, especially the Thinkware one for 20 bucks. There are some that are not as dark as others, however. Polarizing filters have what is called a "filter factor" (ND factor) which is the measurement of the amount of light transmission the filter blocks entering the camera lens. This can be as much as two full ƒ/stops or more. The finest, most expensive polarizing filters available are manufactured by HOYA in Japan and they provide the lowest light transmission penalty of any polarizing filters on the planet, as low as only one ƒ/stop. They are not ""virtually clear", although they are indeed somewhat less tinted than certain others. I happen to know first hand because I own a HOYA HD polarzer. It is dark and looks like any other CPL. I do photography professionally.

HOYA | HD CIR-PL

hoyafilter.com

 

[DAP]

A CPL filter performs the same function as a polarizing filter when used on cameras. A CPL filter is a polarizing filter followed by a sheet of a material that has two indexes of refraction, one for each polarization direction. This is placed at 45 degrees to the polarizing filter and results in spinning the polarization of the light that passes through both filters.

There were some cameras whose auto focus sensors could be confused when attempting to focus on polarized light so they would not work with a simple polarizing filter. the CPL filter avoided this problem by spinning the polarization after polarizing the light. (I don't know why they bother with CPL on dashcams, they could just use polarizing filters. Dashcams are fixed focus cameras. I don't believe any dashcam would have trouble with polarized light.)

The purpose of the polarizing filter is to block light of a particular polarization. This is useful because light that glaces off water, glass or other shiny surface becomes somewhat polarized. By aligning the polarizing filter to block the polarized light reflecting off your windscreen, you will reduce the brightness of the reflection of your dashboard. It will also reduce the brightness of the sunlight reflected of other cars windscreens and give you a better chance of seeing what the other drivers are doing. The sky is also slightly polarized, and the polarizing filter will make the sky a darker blue. Tempered glass tends to rotate the polarization of light slightly, and can result in colored patterns in the sky that change with the orientation of the car when filming through side windows, or the rear window, but not the front windscreen. All windows in a car but the front windscreen are tempered glass. The front windscreen is not tempered, but is instead laminated glass. Tempered glass tends to shatter completely when broken, laminated glass cracks but does not collapse, so gives you a better chance of still being able to see where you are going when it gets broken.