CPL filter? Would you recommend?

[Dashmellow]

If that is correct then my statement is not true. LOL

Have a CPL filter sitting on my old DOD dash cam, which won't be coming home until late next week, but never observed any major light loss when I put it on. Maybe it should be peeled off now ?

You may not have noticed any "major light loss", because the camera will compensate for the CPL with a slower shutter speed so you actually won't see much of any light loss but if you compare images made with and without the CPL you will observe an increase in motion blur, especially in lower light settings. This is simply the way the physics of light and dash cameras work.

Peeled off? How have you got the filter attached to your lens?

 

[DT MI]

...but never observed any major light loss when I put it on...

As @Dashmellow indicated the light loss is there but the camera adjusts for it if possible.

These 2 clips show the amount of loss. Same camera, same car, same location, same light conditions - the only difference being 1 clip is with a polarizing filter and the other without. Now this is an extreme example because it's a rear camera through very dark privacy glass but clearly demonstrates the amount of light loss.

Without filter -

With filter -

 

[Dashmellow]

Here's a good example of the difference between having a CPL on your camera or not having one as far as motion blur is concerned.

One of my cameras is a Mobius 1S 2K cam with an 8mm 12 megapixel ƒ/1.8 telephoto lens on it. The camera is custom fitted with a unique 37mm HOYA HD polarizer. HOYA makes the finest polarizers available and this particular one transmits a full ƒstop more light to the sensor than any other CPL on the market except the even higher quality (and price) HOYA HD3 HRT polarizer they have come out with since. You can read more about the original HOYA HD polarizer I have on this camera HERE.



Anyway, here are several screen shots taken with the same camera on different cloudy overcast days. One image was taken without the polarizer yet clearly captures the plate number as the oncoming car and I approached each other at 40+ miles per hour.

The second image was captured on the same road, also at 40+ miles per hour on an overcast day but with the CPL on the camera and you can see that the oncoming car is affected by motion blur. The motion blur with this CPL which performs better than most is noticeable but usually tolerable. I can basically still make out the plate number but not quite so easily. However, you can certainly see the difference between having a CPL on the camera or not in overcast lighting.

Occasionally, with the CPL on the camera the motion blur can be much worse as seen in the third image. What is different in this image is that it is on hour later in the evening and actually darker out but the camera has compensated and so the image doesn't really reveal that.

All in all the superior performance of this CPL in most situations is the reason I went to the trouble of figuring out a way to mount a filter of this size on this particular camera but it is still a CPL and has the same drawbacks as any other.

No CPL


With CPL

 

[AS87]

To check the glare arising from the dashboard, I removed the CPL and refit it first and then manually adjusted it to the point where I could achieve minimum possible glare.

Link to the video

This is from the Viofo A229 Duo

 

[Landbo]

As @Dashmellow indicated the light loss is there but the camera adjusts for it if possible.

These 2 clips show the amount of loss. Same camera, same car, same location, same light conditions - the only difference being 1 clip is with a polarizing filter and the other without. Now this is an extreme example because it's a rear camera through very dark privacy glass but clearly demonstrates the amount of light loss.

Without filter -

With filter -

Honestly, I sense that it is an ND16 filter the man uses on his rear dash cam in video no. 2. In fact, I think it is completely unrealistic that a CPL filter will dampen as much as he shows.

 

[Landbo]

You may not have noticed any "major light loss", because the camera will compensate for the CPL with a slower shutter speed so you actually won't see much of any light loss but if you compare images made with and without the CPL you will observe an increase in motion blur, especially in lower light settings. This is simply the way the physics of light and dash cameras work.

Peeled off? How have you got the filter attached to your lens?

Yes, of course, a longer shutter speed will generate more motion blur, but it is also a matter of concern whether a correctly mounted CPL filter will create a clearer image with regard to reflections. As I said, I want to investigate how much the CPL filter on my DOD camera dampens when it comes back home.

The words "Peeled off" is just the Google translate translation of the word remove. LOL

 

[DT MI]

Honestly, I sense that it is an ND16 filter the man uses on his rear dash cam in video no. 2. In fact, I think it is completely unrealistic that a CPL filter will dampen as much as he shows.

Well, you think wrong. The filter used in that video is the one I did as a DIY as shown in this thread.

"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

 

[Dashmellow]

Yes, of course, a longer shutter speed will generate more motion blur, but it is also a matter of concern whether a correctly mounted CPL filter will create a clearer image with regard to reflections. As I said, I want to investigate how much the CPL filter on my DOD camera dampens when it comes back home.

The words "Peeled off" is just the Google translate translation of the word remove. LOL

This discussion between us began when you said that the effect of a CPL is "negligible" which I still maintain is not true with most CPLs. Most CPLs decrease exposure by approximately 2 ƒ stops.

You are talking about two completely separate things here. Whether a CPL functions well to ameliorate reflections is a separate issue from how much light is blocked from entering the lens and how much it may affect your shutter speeds. CPLs do indeed behave as ND filters to one degree or another.

The light loss through a CPL filter is negligible.

Just because you don't perceive the light loss from you CPL in your videos doesn't mean it is not happening.

Have a CPL filter sitting on my old DOD dash cam, which won't be coming home until late next week, but never observed any major light loss when I put it on.

 

[Landbo]

Well, you think wrong. The filter used in that video is the one I did as a DIY as shown in this thread.

"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

Well, you've probably gone too far when you use some old dark sunglasses as a CPL filter when the conversation revolves around a regular CPL filter. Therefore, it is an extremely bad example that you pull out of your pocket, so my assumption about an ND16 filter is probably not completely wrong.

 

[Landbo]

This discussion between us began when you said that the effect of a CPL is "negligible" which I still maintain is not true with most CPLs. Most CPLs decrease exposure by approximately 2 ƒ stops.

You are talking about two completely separate things here. Whether a CPL functions well to ameliorate reflections is a separate issue from how much light is blocked from entering the lens and how much it may affect your shutter speeds. CPLs do indeed behave as ND filters to one degree or another.



Just because you don't perceive the light loss from you CPL in your videos doesn't mean it is not happening.

I think you should respect that there are also others who have an opinion than yours. And to repeat myself, I have not experienced a noticeable loss of light with the CPL filter on my old DOD dash cam.

 

[Cyker]

Well the camera will compensate for the lower light by increasing exposure time, so the image it shows will look the same brightness as without the CPL. For still/low speed you will not notice the difference.

It'll only show in low light and darkness, where there will be more motion blur, but you'd just think it is normal unless you have 2 cams running with and without in order to compare.

Basically the choice boils down to remove reflections (CPL fitted) or lower motion blur in lower light conditions (CPL 'peeled off' ).

 

[Dashmellow]

I think you should respect that there are also others who have an opinion than yours. And to repeat myself, I have not experienced a noticeable loss of light with the CPL filter on my old DOD dash cam.

You can't argue with physics.

 

[Dashmellow]

To check the glare arising from the dashboard, I removed the CPL and refit it first and then manually adjusted it to the point where I could achieve minimum possible glare.

Link to the video

This is from the Viofo A229 Duo

 

[Nigel]

I think you should respect that there are also others who have an opinion than yours. And to repeat myself, I have not experienced a noticeable loss of light with the CPL filter on my old DOD dash cam.

Now that you have a Viofo STARVIS 2 dashcam, you may not be noticing a difference in motion blur either, since adding a CPL to a STARVIS 2 camera doesn't necessarily increase motion blur!

You can't argue with physics.

Of course you can argue with physics, you can argue about anything! You may be wrong, but you can still argue.

 

[Dashmellow]

Of course you can argue with physics, you can argue about anything! You may be wrong, but you can still argue.

But as you point out, you would still be wrong.

What is your point? Arguing for argument's sake?

Wait! I almost forgot, you do like to do that.

 

[Dashmellow]

Now that you have a Viofo STARVIS 2 dashcam, you may not be noticing a difference in motion blur either, since adding a CPL to a STARVIS 2 camera doesn't necessarily increase motion blur!

Actually, unexpected motion blur has been one of the major complaints about the Starvis 2 and indeed one of the surprising disappointments from an otherwise excellent advance in sensor technology.

So, I know this might be an unpopular statement, but I'm not happy with the A139 Pro with HDR turned on. No matter whether it's day or night, I feel like I'm seeing far too much motion blur in everyday use.

 

[Nigel]

Actually, unexpected motion blur has been one of the major complaints about the Starvis 2 and indeed one of the surprising disappointments from an otherwise excellent advance in sensor technology.

Yes, so far Starvis 2 has been a bit disappointing on motion blur, but you can add your CPL without making it worse.

 

[Dashmellow]

Yes, so far Starvis 2 has been a bit disappointing on motion blur, but you can add your CPL without making it worse.

I don't buy that thinking. Ever since they announced the Starvis 2 you have been ascribing it with magical abilities it doesn't quite seem to really have. It is an excellent advance, especially for dynamic range but it is still a flawed (for dash cam service) product. It is certainly not immune to the exposure effects of using a CPL filter over the lens. Again, that's due to the physics of light transmission through polarized tinted glass.

 

[Cyker]

It depends on the light saturation or whatever the term is i.e. at a certain point there will be so much light available that it makes no difference whether the CPL is on or not, as the camera sensor is getting as much as it needs for minimum exposure.

At low-light and night it's gonna always be worse tho' - There's no getting around the fact that it's filtering out roughly 50% of the incoming light (i.e. all the vertical... photons?... are getting blocked and only the horizontal ones are getting let through... or the other way around. Something something badgers?), and that will force the sensor in to longer exposures to hold the perceived light level (I used to try setting the EV to negative values to reduce night-time blur on my A119v3, based on this premise, but I could never tell if it worked or not because then I couldn't see anything! )

 

[Karagandinez]

CPL=on
EV=-1/3