Projector vs. Reflector - What's the difference?

When upgrading to HIDs and researching how to go about installing your kit, you'll often come across many debates about projector housings and reflector housings and how they affect an HID upgrade.  There are a few dominant opinions about this topic on the internet that are both conflicting and incorrect.  Let's dispel the myths, get the facts straight, and help you determine how best to improve your vehicle lighting experience.

Biggest Myth: "Reflector housings are not made for HIDs"

Lexus IS HID Stock Reflector HousingsUnfortuantely, for all the naysayers out there, this is not a true statement.  When HIDs were first introduced to the car market in the late 90's, they all came in a reflector housing.  Case in point, the 2001-2003 Acura CL, 2001-2003 Lexus IS, GS, and LS series.  Each of these vehicles used a D1/D2 series HID bulb in a reflector housing that controlled light output.  These housings were designed with HID light output in mind and were designed with "glare caps" placed over the bulbs to control how light was emitted.  Today, many manufacturers have adopted this type of "Glare Cap" for their own halogen housings, making them comparable to the above mentioned vehicles when converted to HID. The basis of the myth that reflector housings were never meant to be used with HIDs stems from the improper installation of HID kits in older vehicles that do not control light well and are not capable of minimizing glare from the additional light to oncoming traffic.  This is not to say that all reflectors work well with HIDs; that would also be a false statement.  Some reflectors work better than others and you just don't know how it will perform until you try.

How exactly does a Reflector work vs a Projector Lens based headlight system?

Reflector: From the light source, light bounces off the rounded surface of the reflector housing and is directed outward focusing light in one direction.  As you can see from the photo below, light is distributed in many different angles in the manner as a halogen flashlight.  This method, although adequate, involves a lot of wasted light as not every beam is directed properly and can angle off too far up or down which is not visible to the driver.

Projector:  From the light source, light bounces inside an elliptical housing before escaping to a concave lens that straightens out the light path directing each beam in the same uniform direction.  This provides better lighting because light output is more tightly controlled and all light is directed through the concave lens.  You will also notice a shield in a projector lens that blocks light from illuminating the top half of the light pattern.  This blocking of light is most commonly known as the light cut-off and is responsible for the sharp beam pattern associated with HID lighting.  A projector lens wastes less of the light source and provides more beams of light pointing in the right direction over reflector based lighting.

 
Traditional Reflector Housing Light Path
 		 Projector Housing Light Path
 
halogen_reflector_light_output_diagram


How does this affect HID lighting?

The light output of an HID system in a reflector based housing is entirely dependent on the design and manufacture as each housing uses different angles and shapes to achieve optimal light output.  This is because the size of the reflector housing typically changes to match the profile of the vehicle.  With new vehicles on the road today, reflector housings actually control light with both halogen bulbs as well as HID bulbs extremely well with the inclusion of what's known as an Anti-Glare Cap, that limits light output and cuts down on stray light patterns.  See the below photo to see an example of the Anti-Glare Cap, and light output of an HID system in a reflector housing + Anti-Glare Cap.

Headlight Housing With and Without Anti-Glare Cap
halogen_headlight_glare_cap_comparison
2011 Hyundai Elantra HID Output using a Halogen Based Reflector Headlamp With Stock Anti-Glare Cap
 
xenonsupply_2011_hyundai_elantra_low_beam_hid_light_output_stock_reflector_housing
In terms of lighting performance, the HID system installed into the Halogen based Reflector housing is very good. There is little to no excessive light above the main beam pattern and light is distributed evenly.  The 2011 Hyunda Elantra in particular is quite receptive to an HID lighting upgrade and its improvement in lighting is fantastic over halogen.

 

In comparison, the below photo shows the light output as well as light pattern control of a Projector Lens based system.  Notice the further improvement in light distribution and the sharp cutoff at the top of the light pattern to control glare.  This is taken from a 2011 Hyundai Sonata that came with stock Halogen Projector Lens upgraded with XenonSupply HIDs.

/xenonsupply_2011_sonata_projector_hid

Simply put, HIDs installed in reflector housings must be judged on a per vehicle basis as the lighting performance varies depending on make, model, and year.  In general terms, newer vehicles whether they are economy cars or luxury cars, will accept an HID upgrade much better than, say, a 1990 Honda Civic.  Systems with Anti-Glare Caps already installed by the manufacturer do exceptionally well with HID lighting by controlling light output and limiting glare.  Projector lens based headlight housings will always perform better than reflector based systems because of their use of the concave lens and elliptical reflector cup.

I hope you all enjoyed this brief overview and as always, if you have additional questions please let us know.  Our support staff can always be reached at Help@XenonSupply.com to answer your technical questions. KYHUZVAVPZ4B

Cheers

Phil @ XS