VMS5240B - What capacity micro SD cards should I order to archive 30 days 4K video?

[GaryStrand]

Just placed order for 2 camera Ultra 2 with smarthub

Plan to record/save video locally:

What capacity micro SD cards should I order to archive 30 days 4K video?

I have no clue how much storage my 2 Ultra 2 cameras and 1 Pro 3 requires?
My main goal is to record traffic on our not too busy court and hopefully have resolution to read license plates? Cars will fully stop facing one camera 100 feet away.

Thanks

[StephenB]

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@GaryStrand wrote:
hopefully have resolution to read license plates? Cars will fully stop facing one camera 100 feet away.

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I expect that won't work.

The cameras use passive infrared (PIR) sensors to detect motion.  The nominal detection range is 20-25 feet.  Vehicles often are detected from much further away, but you aren't likely to trigger on all of them at 100+ feet distances.

Also, the field of view of the cameras is very wide.  Normally cameras designed to read license plates are using a narrow field of view, so that the license plate uses a lot of pixels in the image.  This is measured in pixels per foot (general recommendations are that you need at least 40 ppf, and preferably around 80 ppf).  You certainly won't get that from Arlo cameras at 100 feet.

Lighting is also a factor - headlight glare will make it difficult (likely impossible) to see the license plate at night.

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@GaryStrand wrote:

What capacity micro SD cards should I order to archive 30 days 4K video?

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I think 128 GB should be more than enough.

Arlo's nominal bitrate for 4K is 2 megabits per second (actual bitrate is less than that).  At that rate, 1 minute of video requires about 15 MB of storage  - 60 seconds * 2 megabits / 8 (to convert megabits to megabytes).  128 GB can hold about 140 hours of video at that rate (in practice it will hold more, since the nominal rate is higher than actual).

[GaryStrand]

Stephen
Thanks so much for your timely and detailed technical responses. Especially about the micro SD 128Gb storage.

Still "hoping" to read license plate during the day? I did not consider the headlight glare.

Install and testing next week!

[StephenB]

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@GaryStrand wrote:

Still "hoping" to read license plate during the day? 

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I can make usually make them out around 30-35 feet or so from my Ultra, if I pause the video and zoom the image on my phone. But not at 100 feet.