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What’s the ‘Darkest Legal’ tint?

Everything you need to know about tinting your car to the darkest legal limit.
Dark tinted car

A “Darkest Legal” tint is one of the most popular tinting choices drivers make. Dark windows make a great improvement to the look of your car, whilst maximising driver and passenger privacy and reducing glare. 

What exactly does “darkest legal” mean though? Is there one particular brand of film that’s “the” darkest legal film available on the market? 

Let’s break down the term.

The darkest legal limit for tinting is based on what the governing body for roads (Vicroads in Victoria) determine to be a safe level of visibility for driving. It is the minimum percentage of light they require to pass through your car’s windows, and is measured with an instrument called a lightmeter. 

The smaller the percentage of light transmission, the darker the window. Hence a completely clear window would give a lightmeter reading of 100% transmission, while a completely blacked out window would give a lightmeter reading of 0%.

Lightmeter showing 100% light transmission
A lightmeter showing 100% light transmission.

In Victoria, the law for window tinting requires a minimum of 35% light transmission for the driver and front passenger windows, and a minimum of 20% light transmission for all windows rear of the driver. 

It is often assumed that to achieve light transmission of 35%, we can simply apply a film with 35% light transmission to the window. What’s important to realise though, is that automotive glass is not 100% clear, and light transmission is determined by the combination of glass and film.

Lightmeter showing 77% light transmission
This car window shows a 77% light transmission with a lightmeter before any tint has been applied.

Most modern auto glass has a very small amount of ‘factory tint’, so light transmission before window film is applied is usually between 70-85%. This means that If we were to apply a window film with 35% light transmission to a window that only has 77% light transmission to begin with, the result would be darker than the legal limit (35% of 77% = 26.95%).

That’s why no one film is “the” darkest legal film. Having your car tinted darkest legal means having your tinter find a film with a light transmission that gets your windows as close to the limit as possible, without going darker. A film that gives a darkest legal result for one car might be too dark or too light for another car, so testing a few different options is essential. 

Lightmeter showing 43% light transmission
This window film shows a 43% light transmission with a lightmeter before it has been applied to glass.
Lightmeter showing 35% transmission
The combination of the 77% transmission window and 43% transmission film results in a darkest legal tint of 35%.

Fortunately, a darkest legal tint can be achieved with almost every brand of film on the market, as each film type generally comes in multiple levels of light transmission. By stocking each film in a variety of different levels of light transmission, your tinter can ensure you get the darkest legal result you are after, whichever brand of film you choose.