What To Look For In A Dash Cam

[DashCamManToo]

In my research, I have found that there are basic criteria to consider when weighing the pros and cons of various brands and their products.

Image Quality
If you know anything about video cameras and video recordings, there can never be enough resolution or frame rate. The bottom line is that it will always depend upon the processing power of the hardware in the device. Every year the circuitry gets smaller and more powerful; just like in computers.

This means that we should buy the latest and greatest that we can justify spending our hard-earned money upon. If you can afford an extra fifty or one hundred dollars on better quality video imaging, you may reasonably consider thinking seriously about it. It only makes it better in the long run, because your more powerful camera will be useful longer than a less powerful one, and you will begin reaping the benefits immediately. (Besides, having to learn a new device's idiosyncrasies is always a pain. You don't want to be forced to do that too often.)

The video quality is made up of resolution and frame-rate. Some people like to talk about bit-rate, compression and other factors, but these are things that are based upon the hardware capabilities and there is little difference between brands. It isn't a high-end computer you're buying, so this is not going to be a worry for you. Just keep it simple.

The current high-end video resolution is 4K. This equals 3840 X 2160 pixels, and is called UHD or Ultra High Definition. It is about 4 times the quality of 1080p (a 'p' at the end is about twice as good as an 'i' at the end), or HD (High Definition) at 1920x1080. One can go to 8K, but not in dash cams. Yet.

Just ask yourself, "Would you buy a new television that was not at least 4K?" Of course not. So perhaps the first consideration should be 4K if possible.

Next is frame-rate. This is the number of full screen scans that are recorded per second. Remember that old-time movies were jerky because of very low frame-rates, and our eyes could see the delay between one full scan of the screen and another.

Right now we can enjoy viewing at 30fps, or frames per second. Very good is 60fps. However, most front cams can only offer 30fps at 4K. Again, this is the limitation of the hardware.

This gets a little more compromising when you add a rear and/or interior camera to the front one. Because there is only one processing circuit board in the base unit, the system can only only split the quality so many ways, and the front camera usually gets the priority. Also, the manufacturer will probably only offer an HD camera for the rear or interior.

So there are the current limitations in video quality. I have seen at least one cam that offered a setting of up to 120fps, but I found that to be unnecessary and especially if they lower the resolution to compensate. Therefore we may wish to look for 4K at 30fps.

 

[DashCamManToo]

The Camera
The next issue is the actual cmos image sensor. This is the solid-state device that captures the picture thru the lens at the front of the camera. Everyone has heard of Sony, and they of course make good ones. However, I cannot say anything about the relative quality of the various brands used in dash cams, so I won't try.

Also, of the higher end dash cams, we usually have to go along with the brand that covers other features we're looking for and just trust them to have chosen a good brand for that purpose.

Camera Issues
This brings us to a few features that have to do with the sensor and/or lens arrangement offer in a give camera. Here are those I've noticed as usually considered.
1. Viewing angle
2. Low-light or night sensitivity
3. Polarization
4. WDR
5. Fog-mode
6. Image stabilization

1. Viewing angle is similar to a person's peripheral vision. Since the camera cannot move side to side (or up and down, for that matter), how far can it see to either side? This is the angle that is formed by seeing from the extreme at one side to that of the other side. This can range from 110 degrees to 151 degrees or more. Obviously, the wider, the better, but don't get carried away here.

2. Low-light or night sensitivity has to do with the lack of good daylight to record usable resolution quality. In some modes, infrared lights are used to create brighter images at night. But this usually can only give black and white image recordings. In between full sunlight and darkness there are sensitivity factors built into the sensor and lenses which can enhance in these conditions. Sometimes, there are software processes which can add to the quality as well. Again, we would want the best we can find here.

3. Polarization usually has to do with trying to reduce glare such as is done with some sunglasses with a Polaroid lens. There may be lens combinations built in to handle this, there may be a ring that is available on the lens end of the camera which can be manually adjusted or there may be a filter lens that can be purchased separately to snap onto the lens of the camera.

Consider here if that might be a problem for you. I, for one, can image where people facing cars which are reflecting the sun's rays back toward them which then create a lot of reflections that wash out the surrounding area. This would be bad.

With that said, if you have to stop and snap on a filter lens, that might not be convenient, or even unsafe if done while driving.

So that leaves a built-in feature, or reaching to twist the polarization lens of the camera front. You decide.

4. WDR stands for Wide Dynamic Range. It is that which has to do with the lightest versus the darkest parts of the image view. In our case, this has to do with darkening the too light areas so that they are not washed out, and lightening the too dark areas so that they can be seen. As you can imagine, this is basically an exposure issue. This also has to do with glare in the lighter parts. This correction is done in the processing part of image capture.

5. Fog mode, or similar terms, is that which has to do with weather conditions which are hard for the eye to penetrate. Some camera software can calculate images in such a way that the obscuring conditions are filtered out to create a more useful image.

6. Image stabilization may or may not be an issue for you. A smooth riding luxury car may not have much up and down, or side-to-side, movement, while an old pickup truck might have a serious problem with that. So too anything attached to the car, such as a dash cam.

To fix that, the processing can take that into account and correct for it, if that feature is present. Trying to read a license plate with a jerky camera can be a real issue. Stabilization can help with that.

In summary, you can note how some of these things are based upon the quality of the sensor/lens combination, while others are really based in software processing.

 

[DashCamManToo]

Some Other Things
A dash cam can have two ways of detection motion. One is based upon the g-sensor, or accelerometer, and the other is a motion detector.

The g-sensor will detect side-to-side, up and down, and forward and reverse changes. This is like when the vehicle crashes into another vehicle, or when a shopping cart rolls into the side of the car. It is a physical thing.

The other is detecting when there is movement nearby that is unfelt. This is sensing motion such as kinetic energy from a person walking nearby.

It is easy to see where this is particularly important while the vehicle is parked, but is also that which causes an accident impact to trigger the saving of a video segment during an accident. This is the major function of a dash cam.

Another function that is important is the information that is included with the video. This is the date and time stamp. Further, you may wish to include the vehicle speed and the GPS location. The first part is done in the cam's software settings, and the speed and location is given by the GPS function.

Now here is a bit of a gotcha; believe it or not, some dash cams have no built-in GPS function and must be purchases separately, as bizarre as that may sound. A word to the wise.

What Keeps It All Going
There must be power supplied to the device. The internal storage takes two forms; battery or capacitor. A capacitor is charged up every time it is plugged in, if it has lost charge. While it sounds like a battery, its full charge is instantaneous. Since these devices need some sort of internal power storage, the capacitor is able to withstand higher temperature extremes than batteries and rarely wear out. My suggestion is to go with capacitors when you can.

With that said, there must be a way for the car to give the cam a continuous supply of power. One is to plug into the cigarette lighter socket, and the other is to hard-wire it into the wiring of the vehicle.

In the first case, the device starts up when the key is turned on. In the second case, the device is always running at least in park mode, which may be for a period of 24 or 72 hours, of in stand-by or sleep mode awaiting a sensor trigger at any time. Obviously, the hard-wired option cost for the wiring kit, but gives more time than the internal battery or capacitor can maintain the operation of the cam.

Final Issues
It is always nice to have a built-in display. I do not want to rely upon a smartphone (what a misnomer!) just to see what's being recorded. Further, I want to be able to interface with it thru its own display. That's just how I see it. YMMV.

An SD card slot. There is at least one manufacturer who opts for eMMC storage, which stands for embedded MultiMedia Card, instead of using SD cards. This last longer and is faster, but more expensive. Sadly the offering is usually the bare minimum amount you might want.

So it is nice to be able to buy an SD card of up to 256GB in size, plus be able to pull it out and save it aside while swapping for another one. Remember that these devices will require more expense cards that stand up to continual overwriting, such as the Kingston Endurance cards.

So now you have your videos and you'd like to put them on your computer for further use. The hows and wherefores are important here. Look for ports that include a simple USB connection of some sort to plug into another device. Some offer WiFi or Bluetooth or other odd choices, but nothing beats simple cable downloads in simple USB.

But what do you get? Well, if the videos are in MP4 format and the still images are in JPEG, you're good to go on any platform. Standard formats mean a lot here. Stay away from anything proprietary.

And finally, some brands give you the option of taking a snapshot every so often so you can save a fast view of your trip. Also called time-lapse.

Remember that these devices are just used to save a video clip when needed automatically or on demand. They simply keep recording until the storage medium is full and then start recording over the oldest in the storage. That's pretty much it.

By the way, always take all specs with a grain of salt. The figures presented are only for relative comparisons, and are only accurate if verified by expert review techniques.

Good luck and good hunting!