B1W - Sudden Dark Exposure at Sunset?

[DidYouSeeThat?]

Has anyone else experienced this with their B1W?

I was watching some footage from a drive the other evening, and my B1W had a very sharp and sudden drop in the exposure. It went from normal decent video, to extremely dark, very quickly. The video generally stayed extremely dark from that point on, however it would brighten up to "normal" brightness again any time I went under an overpass. So it appears to be problem with the camera's metering, not an issue of it being too dark outside for video capture. As you can see, the "dark" video is excessively dark, even underexposing the sky.

Short animated gif of the issue is attached below:



I should add that this is with one of the new B1W circular polarizers attached, but I am unsure if the issue is related or not.

 

[ashematian]

I had the same issue a few months back. Apparently the exposure control reference is only a very small ROI box in the center of the video and not the whole frame. You need to aim your camera down a little bit so the ROI is aimed on the road, not the sky.

 

[estore009]

So it appears to be problem with the camera's metering, not an issue of it being too dark outside for video capture.

My team had a check your demo, and they cannot tell you the problem, might be IQ problem!
I agree with @ashematian , give it a try to adjust the camera lens a little down!

 

[Nigel]

Normally we mount the B1W at the top of the windscreen, just low enough for the wipers to keep it's view clear of water and dirt, then I recommend having the horizon in the centre of the image. Normally it goes behind the mirror, since it is wifi you don't need to be able to see it.

You seem to have yours mounted at the bottom?
That means that the horizon is going to move up and down the image more as you go over hills so keep the horizon a bit above the centre, you currently have it a bit below so sometimes it is exposing for the sky instead of the road.

 

[DidYouSeeThat?]

Thanks for the replies.

This B1W is in fact mounted at the top of the windshield, immediately behind the rearview mirror. With such a wide angle lens, the polarizer causes a fair amount of vignetting, making the dashboard & wipers more dark and difficult to see than normal.



I don't necessarily think this situation is an aiming problem. I'll explain why.

Let's assume I *DID* have it aimed too high. The logical outcome is that the camera would see too much bright sky, leading it to compensate by darkening the exposure. But I don't see this issue - my daytime video is well exposed, and as you can see in the beginning of my clip, the near-sundown video (everything leading up to the drop) was also reasonably well-exposed. The camera even overexposed the sky (correctly) to obtain a good overall exposure - something I don't think it would have done if my metering point was aimed too high.

The second issue is that when the camera suddenly darkened, it greatly underexposed the entire image, including the center patch. So even if I did have too much sky in the view, and it was basing the exposure solely on a small center section, it still points to a flaw in the exposure metering as it under-exposed even that central patch. If it had selected a good exposure for the center patch, this change to the overall image wouldn't have been so drastic. It still would have under-exposed, but not by as much.

And thirdly, the camera over-darkened the image in response to lessening amounts of sunlight, even when it still had some exposure/sensitivity in reserve. This is the opposite of what would be expected.... As I mentioned, the camera stayed dark for the remainder of the drive, through all kinds of varying scenery, even though it re-brightened to normal any time I went under an overpass. Granted, driving under an overpass *IS* a darker lighting situation, and brightening the video is the correct behavior... but the overall exposure when dark is still way underexposed...

 

[SawMaster]

Not sure where the metering is taken from with this cam, but try aiming down a bit anyway- always easy to put it back if it doesn't help. It does seem to be overreacting to minor light changes but I can't say why.

Phil

 

[Nigel]

Thanks for the replies.

This B1W is in fact mounted at the top of the windshield, immediately behind the rearview mirror. With such a wide angle lens, the polarizer causes a fair amount of vignetting, making the dashboard & wipers more dark and difficult to see than normal.



I don't necessarily think this situation is an aiming problem. I'll explain why.

Let's assume I *DID* have it aimed too high. The logical outcome is that the camera would see too much bright sky, leading it to compensate by darkening the exposure. But I don't see this issue - my daytime video is well exposed, and as you can see in the beginning of my clip, the near-sundown video (everything leading up to the drop) was also reasonably well-exposed. The camera even overexposed the sky (correctly) to obtain a good overall exposure - something I don't think it would have done if my metering point was aimed too high.

The second issue is that when the camera suddenly darkened, it greatly underexposed the entire image, including the center patch. So even if I did have too much sky in the view, and it was basing the exposure solely on a small center section, it still points to a flaw in the exposure metering as it under-exposed even that central patch. If it had selected a good exposure for the center patch, this change to the overall image wouldn't have been so drastic. It still would have under-exposed, but not by as much.

And thirdly, the camera over-darkened the image in response to lessening amounts of sunlight, even when it still had some exposure/sensitivity in reserve. This is the opposite of what would be expected.... As I mentioned, the camera stayed dark for the remainder of the drive, through all kinds of varying scenery, even though it re-brightened to normal any time I went under an overpass. Granted, driving under an overpass *IS* a darker lighting situation, and brightening the video is the correct behavior... but the overall exposure when dark is still way underexposed...

If you put your mouse pointer on the horizon in the centre of the image at the start of your clip above, by the end of the clip it is over the sky. If the camera is only using the centre pixel for exposure then it is doing what is expected. I'm sure it's not only using 1 pixel, but it does seem to be using spot exposure rather than the road exposure used by most dashcams, but it doesn't have a dashcam processor so I'm not too surprised.

Pointing it down a little will solve that problem except when cresting a hill, but you can never get the crest of a hill right anyway!