Comprehensive Comparison of Commercial H4 Bulbs ~ In Search of the Brightest Halogen Bulb ~

Especially during rainy twilight hours, even with headlights on, it can sometimes feel so dark that you wonder if they’re actually illuminated.

While more vehicles are now equipped with bright light sources like HID and LED as standard, there are still many drivers using cars with halogen bulbs.

Visibility is difficult during rainy twilight even with HID or LED lights, but this is especially true with halogen bulbs. We constantly receive inquiries about brightening headlights, and it’s not uncommon for customers to install aftermarket HID or LED bulbs themselves.

While changing the light source to HID or LED certainly brightens visibility, there are issues to consider.

Since September 1, 2015, headlight inspections during vehicle inspections have changed to low beam testing (limited to vehicles manufactured after September 1, 1998), and most aftermarket HID or LED bulbs fail inspections, even when labeled as “inspection compliant.”

In recent years, whether due to changes in the measurement algorithms of automatic headlight testers at inspection stations or an expansion in inspector discretion, the failure rate has decreased considerably compared to immediately after the transition to low beam testing. However, the failure rate remains high for vehicles with bright aftermarket HID or LED light sources installed in halogen headlight units (though details are unclear, some LED products from well-known domestic manufacturers apparently pass without issues).

Most failing aftermarket HID or LED bulbs have inappropriate light distribution characteristics, producing what’s known as “glare.” Even if visibility is excellent for the driver, it’s reasonable that they fail inspection since creating dangerous conditions for oncoming vehicles is unacceptable.

Therefore, to achieve brightness that complies with safety standards, halogen bulbs remain the basic option.

However, it’s not uncommon to experience reduced brightness after randomly selecting and installing an aftermarket product, making selection quite challenging for many people.

First, choose bulbs with clear glass.

Blue-tinted lenses simply filter warm color components, so with the same filament, they definitely have lower luminous intensity compared to clear ones. Some packages humorously advertise “brightness sensation” when the light just appears whiter!

To provide selection guidance, we measured and quantitatively compared the luminous intensity of five types of bulbs: two standard H4 bulbs and three clear glass H4 bulbs claiming increased brightness (comparing high beams for easier light intensity measurement).

①Koito Manufacturing Standard H4 Bulb V9119-2011

②Osram Standard H4 Bulb V91500555

③Koito Manufacturing Increased Luminosity H4 Bulb V9119-3001

④Stanley Increased Luminosity H4 Bulb RAYBRIG RR79 (no longer in production)

⑥Racing Gear Increased Luminosity H4 Bulb G40P

The Racing Gear bulb notably has a thinner glass tube (compared with Koito’s standard product).

The test vehicle is a Suzuki Palette MK21S with H4 halogen headlight units featuring cut reflectors.

We used the Iyasaka HLT-100 headlight tester.

Since luminous intensity decreases as bulb temperature rises after the headlights are turned on, we measured by quickly finding the point of maximum luminosity.

①Koito Manufacturing Standard H4 Bulb V9119-2011 (415 hcd (hectocandela))

②Osram Standard H4 Bulb V91500555 (408 hcd)

③Koito Manufacturing Increased Luminosity H4 Bulb V9119-3001 (505 hcd)

④Stanley Increased Luminosity H4 Bulb RAYBRIG RR79 (568 hcd)

⑥Racing Gear Increased Luminosity H4 Bulb G40P (613 hcd)

RG Halogen Bulb POWER BEAM 3400K H4 [G40P] Buy on Rakuten

For the low beam light distribution characteristics, none of the bulbs showed problematic glare that would cause issues in vehicle inspections. I should add that bulbs with higher high beam intensity also have brighter low beams, improving visibility.

Among these five types, there’s approximately a 1.5-fold difference between the lowest and highest luminosity, and the Racing Gear product with the highest luminosity clearly improves nighttime visibility. Since brighter bulbs tend to have relatively shorter lifespans, we’re conducting long-term testing of the Racing Gear product, which claims to have design features for extended life.