Nigel
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- Dash Cam
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The first of the Sony Starvis-2 dashcams, the "Pro" model of the popular Viofo A139 dashcam.
The A139 Pro looks and behaves very similar to the standard A139, with the only real difference being the front image sensor, and some extra processing power to handle the 4K HDR video. The standard A139 was probably the best 3 channel dashcam available, depending on requirements, but this, at the time of writing, is the best 1 channel, 2 channel, and 3 channel dashcam! Image quality being far superior to the A129 Pro and Thinkware U1000. I moved over to the A139 Pro from the Viofo A229, and there are a few things that work a little better on the A139, such as connecting the wifi. When you hear the voice announcement that the wifi is connected, you can press the connect camera button on the app, and it works, while with the A229, you need to wait a few seconds, not sure exactly how many, but if you press the app button too soon then it puts you in the setup for connecting the wifi! The A139 and A139 Pro just work correctly, it's obvious that the Pro is a new version of the standard 2K model, so you can expect all the standard features of the A139 to be working properly from release.
The A139 is designed as a taxi / Uber dashcam, with the 3rd channel covering the interior, but the Pro version is available in 1 channel, 2 channel and 3 channel versions, so you can use it for general purpose dashcam use. It is not ideal for making road movies due to having an extra wide front field of view, but since it is the only dashcam that currently has a Sony Starvis-2 image sensor, it is probably currently the best choice for road movies too!
For those wanting a top quality 2 channel dashcam, but wanting a more traditional A129 wedge shaped dashcam, I'm expecting a "Pro" version of the A229 at some point, but that is likely to be several months away. Until then, the A139 Pro 2 channel version is the one to look at. Unfortunately it is only FHD resolution at the rear, while the A229 has 2K at the rear, and the A229 Pro will likely bring some further advantages, but for now, I would sacrifice the 2K resolution to get the new front Sony Starvis-2 sensor. The Starvis-2 is only on the front image sensor at present, I expect the A229 Pro will be Starvis-2 all around.
There is plenty of information on the standard A139, so I won't go into detail on cases, cables, parking modes, etc., they seem to be identical other than the front image sensor. Same type and size of connectors, same interior and rear cameras, fully compatible with the standard model's remote cameras so no need to upgrade cabling or remote cameras, same hardwire kit, etc. So I'll just go over the new stuff, the exciting stuff!
Image Sensor - Sony IMX 678 1/1.8" STARVIS-2
The big features of the A139 Pro are the rather large 1/1.8" Sony Starvis-2 image sensor, and the HDR feature that comes with it. At the time of writing the firmware is still being optimised, so I can't say exactly how much better it is, but if we compare it to the standard A229, which is pretty similar to the standard A139 with both having a Sony IMX335 Starvis-1 image sensor, the advantages are roughly:
- 2.25x the detail in terms of resolution (4K instead of 2K),
- 2.25x the image area (physical size of the light collecting area for a given resolution),
- 2.5x the dynamic range (the ability to record both dark shadows and bright highlights simultaneously),
- half the image noise,
- 7x the sensitivity (the result of which when used in a dashcam should be 1/7th the motion blur,
- and ghost-free multi-exposure HDR that works well and increases the dynamic range improvement to nearly 5x.
Due to the large size of the image sensor, we have 4K resolution instead of 2K while still having the same pixel size, thus in this dashcam, there is no disadvantage of 4K in terms of night vision, and we also have the 7x sensitivity improvement due to Starvis-2! So if you are looking for the best night time dashcam, this is it, even without the HDR. The HDR is the best night time feature, letting you read any plate that reflects your headlights. If you want better than this then you need to look at a headlamp upgrade rather than a dashcam upgrade!
I didn't include bitrate in the above list, partly because it depends on how many channels you are using, and partly because I have been testing development firmware, and that doesn't necessarily have the final bitrates. The sample images below come mainly from 53.3Mb/s video, recorded as a single channel dashcam. More channels reduce the available bitrate, and the image quality does reduce, although even at a "normal" 30Mb/s recording 3 channels, the results are pretty good, it is the unimportant bits of the image that get compressed out.
Field of View
The A139 is designed primarily as a taxicam, with a lot of use in tight spaces in city centre taxi ranks, so has an unusually wide field of view, the A139 Pro continues this with the same magnification in the centre of the image but a little less fisheye, so the total field of view is a little less than on the standard A139 but still far wider than for example the A119 V3 and Mini. As a result a lot of the extra resolution from the 4K sensor is used up giving extra field of view rather than extra magnification. Some people, such as those that do a lot of low speed city driving, will like this, others, who maybe want to be able to read plates at a distance in other lanes on the highway, might prefer to choose a dashcam with narrower field of view, such as the A229 Pro.
The resolution options on the A139 Pro include 4K(3840)x2160 (aspect ratio 16:9) and 4Kx1600 (aspect ratio 21:9). Having a wide angle lens, it is wide angle in both horizontal and vertical, the horizontal is useful for recording more of what is happening around you, the extra vertical field of view is rarely going to be of use, it is better to use the storage (bitrate) for extra detail in the useful part of the image, soI recommend using the 4Kx1600 21:9 aspect ratio setting. Also note that if you are using 3 channels then using the 16:9 4K setting will drop the frame rate to 24 fps, while with 4Kx1600 it will still use 30fps with 3 channels. Due to the wide angle lens, the 21:9 aspect ratio still has a similar vertical field of view to an A119 V3 using the normal 16:9 aspect ratio, but a much wider horizontal field of view.
Power
As might be expected, the 4K Pro version of the A139 uses more power than the 2K standard version, it has twice the resolution and is recording nearly twice the bitrate, but it only uses about half a watt extra, the Starvis-2 sensors have improved power consumption so the increase in power consumption is less than expected. These are approximate figures for 1 channel recording, not including any losses in a hardwire kit, and after the power consumption has stabilized (after the super capacitors are fully charged):
- A139 Standard, 1 channel recording, wifi off = 2.6 watts.
- A139 Pro, 1 channel recording, wifi off = 3.2 watts.
If you have more than one channel then that will increase the power consumption, but by the same amount for both Pro and standard since they use the same remote cameras.
The A139 Pro will use the same hardwire kits as the standard model, although there may be upgraded versions arriving for the higher power consumption. I'm not aware of any issues using the old versions, they were upgraded when the standard model arrived.
If you want to use the camera for parking mode, do take note that with 3 channels recording, this is one of the thirstiest dashcams, your battery runtime will be reduced over lesser dashcams, and it is probably worth looking at using a dashcam powerbank rather than using the vehicle battery. If you do use the vehicle battery then you want a hardwire kit with a low voltage cutoff that can be set quite low since the high power consumption will pull the voltage down a bit, so a cutoff of 11.8 volts will switch the power off at 11.8 volts, but the battery voltage will then recover to maybe 12.2 volts. In other words a normal low voltage cutoff will leave your car battery nearly full and you will get very short battery run times.
HDR
On the A139 Pro, the HDR function provides two advantages, first there is the High Dynamic Range, which allows the dashcam to record detail in the shadows at the same time as detail in the highlights, and second the highlights are recorded using a much faster exposure than the shadows, and thus have far less motion blur than is necessary to capture the shadows, thus the A139 Pro will record license plates on moving cars at night fairly reliably, even at closing speeds of 100 Km/h. I say "fairly reliably" because the plates do need to be illuminated by your headlights, so it won't work if you are not using headlights, or if your headlights have a narrower than required beam to reach the required plate.
Note that with the larger dynamic range of the Starvis-2 sensors, the dynamic range of the image needs to be fairly heavily compressed to fit into an SDR (Standard Dynamic Range) video file. The A139 Pro does however use standard SDR H264 video files, not HDR video files, which results in rather low contrast video which has a lot of detail, but can be a little unimpressive. If you are using it for movie making, you may want to expand the compressed dynamic range in the SDR video file back into the more realistic dynamic range of an HDR video file for display on HDR display devices.
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