The OEM Doctor Looks at 12 Volt Mirrors

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Rear view replacement mirrors with built-in monitors are great for viewing a backup camera or navigation directions.  But there’s a key mirror feature that is too often overlooked.

Mirrors can include Homelink or retain OnStar or Bluelink. But the one thing I have not seen much of a focus on is the heart of the mirror’s performance—brightness.

Mirror monitors can range from a 2.5-inch display to a 10.2-inch superwide clip on.  My observation presently is that the market wants a mirror that looks as factory as possible with a screen size as large as possible.   With that, a 4.3-inch built in LCD seems to be the maximum monitor size available that can still keep the OE style size and aesthetics of the original rear view mirror.

That said, mirrors have shown a major fluctuation over the years relative to quality (Chinese vs Taiwanese vs American) and have proven yet again that in this day and age, “The best price isn’t always a good thing.”

Why Brightness?

There are many features you should evaluate in a mirror monitor such as the number of video inputs. My take, out of the various options, brightness (measured in NITs or CD/M2) is the most important!  While the number of video inputs can help with expansion (2 is usually the average for a decent mirror), and signal sensing gives you automatic video turn on (vs trigger based) it is the brightness that is solely responsible for not only the image brightness, but also the sharpness and the amount OFF AXIS viewing (how clear you can see the image from left to right).

CD/M2 or candela per square metre (cd/m2) is the unit of measurement for luminescence or brightness. The unit is based on the candela, the SI unit of luminous intensity, and the square metre, the SI unit of area.  This is also known as nit or NT.  They have exactly the same meaning and value.   (1NT=1 cd/m2) . To give you an example of its rating, the sun at noon is roughly 1.6 billion NT or cd/m2).

Most mirrors have a brightness of 500-1100 cd/m2 or nits. This is unfortunately the average on the market today when you are dealing with mirrors at prices almost too good to be true.  Viewed by themselves, these mirrors seem to do the job.  But if you place them next to a better mirror the difference will hit you like a pan to the face!

This level of brightness is typically found in some 3.5-inch and cheaper 4.3-inch mirrors that are rectangular in shape and have that generic looking plastic.   Usually they have a mirror bracket that is not interchangeable for different applications (or the bracket is a bolt on). A better mirror will typically have a bracket system much more OEM-centric than a simple bolt on with 4 screws.

A better rating is 1200-1500 CD/M2 (nits).  Now you are talking!  These mirrors are typically found with some of the higher end product offerings and better brands, but you can buy these for a very competitive price!!   Their built-in monitors can range from 3.5- to 7.3-inches super wide and give you the most for your money.

1600+ CD/M2 (nits): these are usually OEM mirrors both certified and validated to meet their standards.   They display a very rich image, with a view from left to right that is more than sufficient.  They are available to our market, but with a much higher cost than average.   If your customer is demanding the best though, this is the way to go.

Why are we limited to 4.3 screen sizes?

As most of you know, we are not limited to sizes of only 4.3.  However, with an ever-growing focus on retaining the factory aesthetics a 4.3 seems to be the maximum size, with its plastic assembly, that will fit in an OEM sized mirror that looks like it came from the factory.

Aftermarket companies, however, are beginning to incorporate larger monitors up to over 7 inches in wide screen 16:9 or even 21:9 super wide LCD’s to give you a larger image.  But the mirror size may increase by 15- 20 percent.  Some of these new mirrors have some great expansion features  such as split screen picture in picture and automatic turn on video inputs.

What does the future hold?

I have seen a few prototypes relative to what the mirror market has in store for the future but I have been sworn to secrecy.  As the companies working on new tech get closer to launch, I am sure they will release my fingertips to do the typing and bring you all in the know!

For now, I hope this guide sheds some light and helps you in offering the best to your clients while keeping your budget in tact.

-OEM Doctor

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