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Dashcam at night

 
Old 05-12-19, 11:16 AM
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energie8
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Default Dashcam at night

Does anyone here have the 4K Blackvue DR900s? Was wondering why my camera is not picking up license plates at night, I've see multiple videos on youtube and it picks it up perfectly but not for me...I've tried in less lighting areas and downtown driving with 6000K HID and standard halogens but it cannot pick it up, settings are default and is on 4K mode.
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Old 05-12-19, 01:12 PM
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Old 05-12-19, 05:26 PM
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A good resource for dash cam Q's: www.reddit.com/r/dashcam
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Old 05-13-19, 06:04 AM
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I've been dissatisfied with the 1080p 30fps.....it can get the plate when directly behind or the car passes, but it's not crystal clear unless behind. What I want to do is to use a 1080p camcorder on a Fat Gecko to compare. Pretty sure the camcorder is really clear, like the vids people do while they are driving/reviewing cars.

I liken it to an iPhone with a gazillion megapixels and tiny 1 or 2 lenses. Takes awful pics. Then you get a DSLR with 6 MP and a SLR lens, takes awesome pics. I bet this is all about the lens and sensor. But a dashcam is better than nothing. Don't some even use a gopro?

edit I was also thinking it may not be possible for any cam to see what we do. In bumper to bumper today, I could look across 8 lanes of traffic--vehicles 1 car length away both directions, I can read the license plates with my slick Maui Jim brilliants! The cam cannot...

Last edited by Johnhav430; 05-13-19 at 06:08 AM.
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Old 05-13-19, 11:53 AM
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Originally Posted by ABC View Post
A good resource for dash cam Q's: www.reddit.com/r/dashcam
I prefer to go to Dashcamtalk.com, their site is very active and filled with comprehensive information.
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Old 05-13-19, 12:07 PM
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Originally Posted by Johnhav430 View Post
I've been dissatisfied with the 1080p 30fps.....it can get the plate when directly behind or the car passes, but it's not crystal clear unless behind. What I want to do is to use a 1080p camcorder on a Fat Gecko to compare. Pretty sure the camcorder is really clear, like the vids people do while they are driving/reviewing cars.

I liken it to an iPhone with a gazillion megapixels and tiny 1 or 2 lenses. Takes awful pics. Then you get a DSLR with 6 MP and a SLR lens, takes awesome pics. I bet this is all about the lens and sensor. But a dashcam is better than nothing. Don't some even use a gopro?

edit I was also thinking it may not be possible for any cam to see what we do. In bumper to bumper today, I could look across 8 lanes of traffic--vehicles 1 car length away both directions, I can read the license plates with my slick Maui Jim brilliants! The cam cannot...
If the video is reading a plate closeby, then it is very clear.
However, if the video is reading a plate far away, it is almost impossible to read.
This is NOT really going to be solved by 4k resolution, and that's why a number of dashcam manufacturers have been reticent to move into 4k resolution - and 4k resolutions for any given sensor size makes the pixels smaller - which in turn collects less light for compromized low light performance.

They can "electronically" amplify low light areas by boosting the ISO, but this also electronically amplifies the "background" noise, resulting in a "noisy" image.






The real reason why dashcams cannot read plates far away is due to focal length and field of view FOV.
Previously, the Blackvues were using a 139 degree front camera.
Now, the latest Blackvue DRS900 4k dashcams are now using 162 degree front wide angle vision.

To get this very wide 162 view angle, shorter focal lengths must be used.
As the focal length gets shorter and shorter, there is more "perspective distortion".
Perspective distortion makes the front eg nose appear much larger, while the rear eg pony tail appears much smaller.
Hence almost impossible to read licence plates far away.

Longer focal lengths give "flatter" images, and that's why your photographer will use at least 85 mm long focal lengths to do portrait photography of you.

4k resolution partially helps to read plates far away, but compromizes low light performance in the process.

Two longer focal length lenses with narrower viewing angles to minimize perspective distortion, each with larger sensor size and larger glass lens would help low light performance - but then a much bigger, more expensive, and much less covert dashcam.

Cell phones now have multiple lenses and sensors to overcome focal length issues...



.

Last edited by peteharvey; 05-13-19 at 12:44 PM.
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