CPL Reduces Quality?

[TekkieNYC]

Greetings and Happy New Year,

I've noticed a reduction in detail/sharpness when using CPL. The CPL does help with keeping dash reflection to a minimum but quality suffers slightly in the day, and a lot at night.

At night the quality wasn't great to begin with, but with the CPL it's visibly blocky. CPL has zero affect on glare from street lights, traffic lights, car lights. A very clean windshield does not resolve glare issues.

So back to my question, does CPL usually reduces quality? Thanks.

 

[Dashmellow]

A CPL requires an increase of exposure because it is blocking some of the light going to the sensor (like sunglasses in front of your eyes) but it should not effect detail or sharpness at all. The increased exposure will increase motion blur but that should be the extent of it. Perhaps that is what you are seeing? It definitely will not cause "blocky" video which is a different issue entirely.

Check to make sure that your CPL is clean and in good condition. Some dash cam CPLs have been known to delaminate (layers of glass becoming unglued) or can have other problems. For example, one of the Street Guardian CPLs I received had numerous tiny pock marks in the glass and what may be some tiny bubbles. If you find a defect, ask for a replacement.

If you find the CPL has some fingerprints or other contamination clean it VERY carefully with good quality lens fluid and appropriate cleaning cloth or lens paper. Always blow off any any lens surface before attempting to clean it to remove dust and particles and NEVER wipe a dry lens surface.

If you don't find a specific problem with the CPL but are still not happy with the performance consider a good quality dash mat. Dash mats can often work just as well or even better than a CPL.

 

[TekkieNYC]

I thank you for elaborating the basics to me on how to clean a lense, and what a CPL (like sunglasses for my eyes) does.... The observation still remains the same as the quality slightly suffers, the exposure is quiet fine.

You're telling me the processor is not overloaded with a CPL on, which in result may slightly degraded dash cam performance?

 

[Dashmellow]

Firstly, I was suggesting that you make sure that there were no smudges on the camera lens or the polarizer and to check to make sure that your CPL has no obvious defects to eliminate that as a possible cause of your problem.

Secondly, I wanted to make clear that the CPL cannot in any way cause "blocky" looking footage. (usually referred to as Macro Blocking)

Thirdly, I tried to explain that since a CPL blocks some of the light going into your camera's lens (using the sunglasses analogy) that it makes the camera work harder to achieve proper exposure using a slower shutter speed.
The slower shutter speed will give you a good exposure but it can increase to one degree or another what is called motion blur and that may be the source of your degraded image.

If motion blur is especially bad it can look like this photo below but in more subtle forms can simply make your images seem less clear and detailed.
Notice that the moving bus is blurry but the motionless phone booth and road surface are sharp and clear.



Perhaps there is some other problem going on with your camera?
Often it helps if you post some samples here on the forum for members to evaluate.

 

[TekkieNYC]

I appreciate your feedback. Thank you.

Motion blur is minimal and is only apparent at high speeds like on a bridge, which is normal.

 

[TekkieNYC]

Here is a lossless upload from a little while ago. Pay attention to image quality itself and the road.

https://we.tl/6JkzxLCU9y

mute it, it gets loud a few times to demonstrate how speed affects video quality.

PS the dash cam is position to the right of the rear-view mirror, thus you see right more...

 

[Dashmellow]

Just to make sure, are you saying that this problem goes away when you remove the CPL?

If that is the case, then the CPL "might" be interacting with your windshield, which can happen in certain vehicles. Usually, when that happens there can be a rainbow effect, color shift or bar patterns but there can be other issues depending upon on the way the windshield glass was manufactured.

If the problem persists without the CPL then there is likely some other issue with the camera itself or the CPL has some unusual problem.

 

[Viking]

Greetings and Happy New Year,

I've noticed a reduction in detail/sharpness when using CPL. The CPL does help with keeping dash reflection to a minimum but quality suffers slightly in the day, and a lot at night.

At night the quality wasn't great to begin with, but with the CPL it's visibly blocky. CPL has zero affect on glare from street lights, traffic lights, car lights. A very clean windshield does not resolve glare issues.

So back to my question, does CPL usually reduces quality? Thanks.

Did you do the same as me?

Check this: https://dashcamtalk.com/forum/threads/viofo-a119s-videos.25470/page-9#post-309478

 

[TekkieNYC]

Did you do the same as me?

Check this: https://dashcamtalk.com/forum/threads/viofo-a119s-videos.25470/page-9#post-309478

No film on outside or inside. Is there top or bottom side? I see one side has a much bigger opening that holds the glass vs the other one.

 

[TekkieNYC]

 

[jokiin]

No film on outside or inside. Is there top or bottom side? I see one side has a much bigger opening that holds the glass vs the other one.

large opening goes to the top, won't change the image, just means the glass can't rattle loose

 

[gretl4]

Here is a lossless upload from a little while ago. Pay attention to image quality itself and the road.

https://we.tl/6JkzxLCU9y

mute it, it gets loud a few times to demonstrate how speed affects video quality.

PS the dash cam is position to the right of the rear-view mirror, thus you see right more...

Looks blurry on the left side to me.

 

[DT MI]

Looks blurry on the left side to me.

I agree, the left side looks to be out of focus. I grabbed this frame from your linked clip. Even considering motion blur the left side is much softer than the right. Look specifically at the left and right fenders of your car and it's pretty obvious.

 

[TekkieNYC]

Yes, and I'm not the only one with left side being out of focus... What could this be?

 

[DT MI]

...What could this be?

1. Lens and sensor not parallel to one another.
2. Defective lens.
3. Defective sensor.
4. Lens improperly installed.
5. Something else....

Many different things could be the cause.

 

[Nigel]

At night the quality wasn't great to begin with, but with the CPL it's visibly blocky. CPL has zero affect on glare from street lights, traffic lights, car lights. A very clean windshield does not resolve glare issues.

Can we see a frame grab showing the blockyness at night? (not a huge video to download!)

 

[TekkieNYC]

1. Lens and sensor not parallel to one another.
2. Defective lens.
3. Defective sensor.
4. Lens improperly installed.
5. Something else....

Many different things could be the cause.

A better question will be - who is responsible... Definitely not me the consumer... Right?

 

[TekkieNYC]

Can we see a frame grab showing the blockyness at night? (not a huge video to download!)

I'll set the length to smaller clips tonight on the way home. You guys have bandwidth limits in UK?

 

[DT MI]

A better question will be - who is responsible... Definitely not me the consumer... Right?

Depends on the specific cause. The 'Something else' could be user abuse (dropping it, twisting the lens, etc.).

 

[TekkieNYC]

Depends on the specific cause. The 'Something else' could be user abuse (dropping it, twisting the lens, etc.).

ROFL Ok, so far most of A119S owners report the same issue, we all have abused the dash cam that we've paid for... nonsense.