HeePee
Member
- Joined
- Jun 16, 2017
- Messages
- 43
- Reaction score
- 14
- Location
- Amsterdam
- Country
- Netherlands
- Dash Cam
- VIOFO A119 V2 + GPS
In a nutshell.
The angle of the lens - Bigger is better? Don't think so! The wider the angle, the more details (pixels) you need to process and store. If you have a 170 degrees lens with 1080P resolution, the image quality will be crap. Or, if you have a 130 degrees lens with 1080P and your colleague has a dash cam (and is bragging about it) with a 170 degrees lens with 1296P, then you still win!
Why do you think your phone makes such wonderful videos on 1080p and your dash cam not?! That's because your phone has only a 60 degrees lens angle. So, 1920x1080 (1080p) pixels for a much smaller picture than your dash cam! Your dash cam has to use the same amount of pixels (1080p) for a much wider / bigger picture. So, best to go for a 130 or max 140 degrees lens angle, it gives you sufficient sight on the road.
Video compression - Make sure you buy a dash cam that encodes in H264. It's the best codec and provides much smaller file sizes.
Bitrate - The higher the better. With the codec H264 (video compression); At this moment (what the market does offer @2017), you should buy a dash cam with a minimum bitrate is 15 mbps (1080p ) or 18 mps (1296p), most ideal would be 20 mbps (1440p). The bitrate does not only determine the quality of the video, it also determines the size of the recorded video file (bitrate times seconds = file size). Keep that in mind when buying a SD card.
Wide / High Dynamic range - Don't buy a dash cam that does not offer WDR or HDR. It makes all the difference. Without it, most detail will be lost in shadows. WDR / HDR makes sure that you will have a great light balance. Go Google about it and see the differences.
Lens, CMOS and CPU. Check what lens is being used, what CMOS and CPU (video processor). Look up the specs of the CMOS (the chip that does receive the light from the lens and transforms it into a electrical signal for each pixel embedded on the chip. So, like a solar panel is working). How many pixels has the it, 2M, 3M or 5M? It tells something about the max resolution you get from it. How big is a pixel? The bigger, the more light it can receive. How well does it transform the light into an electric signal? 1.6V, 3.3V? The more sensitive, the better. And what about the CPU (video processor)? The one that builds the video from the electric signals, provided by the pixels on the CMOS. It it fast (bitrate)? How does it encode (H264)? Go comparing lens, cmos and cpu between different dash cam. Google is your friend. Take notice of the Novatek 96650/96660 or Ambarella A7 video processors and the OmniVision OV4689 CMOS. These are today high end chips. But you might not need this high end chips ($), depending what resolution/quality you want.
For a comparison of the video processors, see:
https://dashcamtalk.com/forum/threads/great-specs-overview-of-most-common-video-processors.29447/
Resolution - Important, of course. But only if all off above does apply. Ask your self on what device you want to playback the videos? What resolution is your TV or PC screen? If it's max 1080p, then would you dash cam need more? However, you might want to catch as much detail as possible in case of an accident. With the right video player, like Quick Time Player 7, you can zoom in to watch the video in the original resolution. By zooming in, you can watch 1296P on a 1080p screen. You just don't see the full video picture. But all you want is that license plate, right?
In my view, the more pixels the better, 1440p would be great. That is, with taking into account a great bitrate and a not so big lens angle (130 or 140).
Micro SD card - Don't try to safe any money on the micro SD card. Check the dash cam specs on what types are allowed. Not all dash cams do, for example, support Ultra. Buy one that can support the bitrate and that can stand heat. Also check how many hours of video you can record (life time). Like 10000 or 12000 hours. A good one is the Sandisk Endurance, special made for dash cams. Transcand has also a High Endurance SD card, special made for dash cams. Both Sandisk and Transcand have these Endurance micro SD cards in 32Gb and 64Gb. Note that (also for both) the max write speed is 20Mb/s.
Last the not least(!!) - Always (and really, really always) add a CPL filter to your lens. The one thing that will (for sure and in any case) screw up your video quality is the reflection of your windscreen. No matter how great your dash cam is, the quality will be crap as the reflection of your dashboard will make license plates (on a distance) unreadable. All other things will be grainy. Especially for the lower part of your video. Yes, this is not because of the dash cam, it's because of the reflection. That is why people complain that their dash cam delivers grainy videos. Well, mostly it isn't! It's reflection that can be solved by buying a $15 CPL filer! Note: When you apply a CPL filter, you might need to increase the EV (Exposure Value) with one click up. Just check it out if that's needed or not.
Like a said, in a nutshell. And just basis my experiences so far. I'm sure others have much more to add.
The angle of the lens - Bigger is better? Don't think so! The wider the angle, the more details (pixels) you need to process and store. If you have a 170 degrees lens with 1080P resolution, the image quality will be crap. Or, if you have a 130 degrees lens with 1080P and your colleague has a dash cam (and is bragging about it) with a 170 degrees lens with 1296P, then you still win!
Why do you think your phone makes such wonderful videos on 1080p and your dash cam not?! That's because your phone has only a 60 degrees lens angle. So, 1920x1080 (1080p) pixels for a much smaller picture than your dash cam! Your dash cam has to use the same amount of pixels (1080p) for a much wider / bigger picture. So, best to go for a 130 or max 140 degrees lens angle, it gives you sufficient sight on the road.
Video compression - Make sure you buy a dash cam that encodes in H264. It's the best codec and provides much smaller file sizes.
Bitrate - The higher the better. With the codec H264 (video compression); At this moment (what the market does offer @2017), you should buy a dash cam with a minimum bitrate is 15 mbps (1080p ) or 18 mps (1296p), most ideal would be 20 mbps (1440p). The bitrate does not only determine the quality of the video, it also determines the size of the recorded video file (bitrate times seconds = file size). Keep that in mind when buying a SD card.
Wide / High Dynamic range - Don't buy a dash cam that does not offer WDR or HDR. It makes all the difference. Without it, most detail will be lost in shadows. WDR / HDR makes sure that you will have a great light balance. Go Google about it and see the differences.
Lens, CMOS and CPU. Check what lens is being used, what CMOS and CPU (video processor). Look up the specs of the CMOS (the chip that does receive the light from the lens and transforms it into a electrical signal for each pixel embedded on the chip. So, like a solar panel is working). How many pixels has the it, 2M, 3M or 5M? It tells something about the max resolution you get from it. How big is a pixel? The bigger, the more light it can receive. How well does it transform the light into an electric signal? 1.6V, 3.3V? The more sensitive, the better. And what about the CPU (video processor)? The one that builds the video from the electric signals, provided by the pixels on the CMOS. It it fast (bitrate)? How does it encode (H264)? Go comparing lens, cmos and cpu between different dash cam. Google is your friend. Take notice of the Novatek 96650/96660 or Ambarella A7 video processors and the OmniVision OV4689 CMOS. These are today high end chips. But you might not need this high end chips ($), depending what resolution/quality you want.
For a comparison of the video processors, see:
https://dashcamtalk.com/forum/threads/great-specs-overview-of-most-common-video-processors.29447/
Resolution - Important, of course. But only if all off above does apply. Ask your self on what device you want to playback the videos? What resolution is your TV or PC screen? If it's max 1080p, then would you dash cam need more? However, you might want to catch as much detail as possible in case of an accident. With the right video player, like Quick Time Player 7, you can zoom in to watch the video in the original resolution. By zooming in, you can watch 1296P on a 1080p screen. You just don't see the full video picture. But all you want is that license plate, right?
In my view, the more pixels the better, 1440p would be great. That is, with taking into account a great bitrate and a not so big lens angle (130 or 140).
Micro SD card - Don't try to safe any money on the micro SD card. Check the dash cam specs on what types are allowed. Not all dash cams do, for example, support Ultra. Buy one that can support the bitrate and that can stand heat. Also check how many hours of video you can record (life time). Like 10000 or 12000 hours. A good one is the Sandisk Endurance, special made for dash cams. Transcand has also a High Endurance SD card, special made for dash cams. Both Sandisk and Transcand have these Endurance micro SD cards in 32Gb and 64Gb. Note that (also for both) the max write speed is 20Mb/s.
Last the not least(!!) - Always (and really, really always) add a CPL filter to your lens. The one thing that will (for sure and in any case) screw up your video quality is the reflection of your windscreen. No matter how great your dash cam is, the quality will be crap as the reflection of your dashboard will make license plates (on a distance) unreadable. All other things will be grainy. Especially for the lower part of your video. Yes, this is not because of the dash cam, it's because of the reflection. That is why people complain that their dash cam delivers grainy videos. Well, mostly it isn't! It's reflection that can be solved by buying a $15 CPL filer! Note: When you apply a CPL filter, you might need to increase the EV (Exposure Value) with one click up. Just check it out if that's needed or not.
Like a said, in a nutshell. And just basis my experiences so far. I'm sure others have much more to add.
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