Does Polarization ruin night footage?

[mac782]

Hi,

Am looking at getting CPLs but reading contradictory views on here about whether they work - ranging from 'they're essential' to 'they ruin night imaging so I took it off'.

What do people think - worth getting some?

Thanks,

 

[RoadRage]

So far it's pros and cons. Pro: it does reduce glare and reflections. Maybe it also protects the lens from UV and heat. Cons: tints the video a bit darker. Nighttime is impacted. Regardless of auto adjustments the camera may make, it's definitely not as clear as without the CPL.

 

[kamkar]

A CPL filter do block a little light, but with a modern image sensor in the camera thats not really a problem, and at night with or without CPL there will be no difference in the image properties in general.
I have CPL filters on all the cameras i have where it is a option and / or the camera come with a CPL filter from the factory.

 

[DT MI]

About 4 years ago (before CPLs were generally available) I did a DIY version. In the process I did a bit of testing with and without the CPL on the same camera day and night. (The DIY version was made with material from a pair of sunglasses which is actually a bit darker than most CPLs available for dash cams today.)

Browse through this thread to see the impact on the camera I did the comparisons on, but keep in mind that the positive and negative effects will differ for each camera and CPL:

"Poor Man's" Polarizer for SG9665xx, A118xx, and B40xx

Inspired by Niko's DIY polarizer for the SG9665GC and the discussion that followed in this thread - https://dashcamtalk.com/forum/threads/magnetic-cpl-lens-filter-for-street-guardian-sg9665gc.10942/ - I decided to try doing something with items I had laying around the house and that would work...

dashcamtalk.com

 

[mac782]

Seems like everyone is using them anyway regardless of any negative impact?

 

[mac782]

Here is how the footage are currently looking:

 

[Nigel]

Should give you a big improvement during the day, especially on the back, but double the motion blur at night. Doesn't really make much negative difference in the summer, for dark winter days when you have visible motion blur during the day it may be worth removing it.

For cameras with the more sensitive Starvis sensors it can be left on all the time, DR900S is not really one of them though!

 

[jokiin]

if that's how it looks currently you're probably not going to like it with filters on

 

[mac782]

@jokiin Really? You dont think CPL would remove some of the glare? Are you using filters btw?

 

[jokiin]

@jokiin Really? You dont think CPL would remove some of the glare? Are you using filters btw?

CPL filters remove reflection not glare, the video is not great now, adding a filter is going to reduce light and the camera is going to struggle

yes I use filters on all my front cameras but they're native FullHD which has much larger pixels than the sensor in your camera so they catch a lot more light to begin with, losing some light doesn't have as big an impact on mine as it will on yours

 

[M8TJT]

A lot of the 'glare' in your rear cam shot is not glare at all, it's the reflection of the what looks like a light coloured back parcel shelf (or whatever) on the rear screen. A CPL will get rid of most of that.
A CPL on your front cam will pretty much remove the reflection that you are getting off your bonnet and also the reflections of your dash in the windscreen.
That's what they do. As well as severely reducing reflections of the sun/headlights from a wet road.

You can reduce real glare quite a bit by not including less sky and more dashboard. After all, it's just the road that you are interested in and why dashcam makers don't include a 'letterbox' aspect ratio option so that you can cut out a lot of sky and dashboard, I don't know.

 

[SawMaster]

Seems like everyone is using them anyway regardless of any negative impact?

Those who do not understand them do this, and it is not helping when sellers and manufacturers push them as being 'necessary'.

Each case is an individual. If you need a CPL for reflections etc then they do help- sometimes considerably. If you don't need them they can detract from performance especially in low light- sometimes considerably. If you're happy with what you're getting without a CPL that's all you need and it's not going to much improve on that if at all. More is not always better

Phil

 

[M8TJT]

Agreed, but especially the rear cam view in post #6 shows dreadful reflections of the rear parcel shelf which is diluting the contrast of the picture horribly. Just look at the contrast between the kerb and the reflection. Pretty much the same 'strength'. (the front is not as bad, but it's still there)
CPLs would almost completely remove the reflections and boost wanted picture quality/contrast.

 

[mcmanus]

What I have found so far with the CPL I purchased.

During the winter months I did not use it (primarily driving in darkness). During Spring it has been great to have as the angle of the sun when I drive to work can be very low, and it does make a difference when driving directly into the sun. I'll likely leave it on until winter sets in again.

 

[M8TJT]

You said you chose not to use it during darkness. What exactly were the negative effects that made you decide this, as that's what the thread is originally about?
Personally, I haven't tried a on/off comparison and I was just commenting on the effect a CPL would likely have on the daytime shots in post #6 which shows really bad reflections esp. at the rear.

 

[mcmanus]

You said you chose not to use it during darkness. What exactly were the negative effects that made you decide this, as that's what the thread is originally about?
Personally, I haven't tried a on/off comparison and I was just commenting on the effect a CPL would likely have on the daytime shots in post #6 which shows really bad reflections esp. at the rear.

It just makes everything a bit too dark. In the winter we have very short days my commute is entirely in the dark and I do not get terrible reflection so I just remove it. From Spring on I just leave it be. We get way longer days.

 

[RaggedEdge]

I made a few videos that show the 900s with CPL filter on and off, both daytime and nightime.

Daytime:

Night time:

 

[M8TJT]

Nice comparison. Seems to improve the pic at night by reducing glare from the streetlights.

 

[Rick Needham]

Nice improvement all around if you ask me. Thank you for posting the day and night videos.

 

[RoadRage]

Which CPL filter are you using Ragged? The one I got off Amazon seems to darken the image quite a bit compared to yours. I like yours better.