Domed vs flat lenses, which is better?

[Stanley Rockafella]

I noticed when shopping for headlamp conversion kits online, that they offer both types when looking at Cibie lamps. Just wondering if there's any lighting benefit of the one over the other?

http://www.headlightservices.com/Headlamps.html

[dsphil]

It depends how the lens was design to divert the light beams. GE, wagner, and Sylvania sealed beam has different beam patterns because each lens design differently. I think the hella h4 lens has to be flat design in order to achieve their desired beam pattern result.

Edit: I hope the flat lens look didn't got on you too..

[15Michaeljoseph]

I might just be stupid but a flat face, to me, is going to have a more foreward, projector-like euro cutoff, whereas the domed design would splash more light around the outsides for a more peripheral, US-spec cutoff.

again, idk. I'm running Hella H4's with the flat face.


--Mike

[ELVA164]

Flat-face lenses generally work better.

[Stanley Rockafella]

Flat-face lenses generally work better.

but why? is there any evidence to support this?

[ELVA164]

This sounds kinda smartassey, but all the high-performance headlights I've seen on older cars (road or race) had flat lenses. Obviously not definitive, but it seems like a strong pattern.

[LateFan]

I've seen both, like old Cibie and Marshal lights with a nice curved face..



It could be the style of the time...OR…it could be flat makes the math easier for all the refraction angles..? I have no idea.

But you can find out the specific output / performance of a light / reflector / bulb combination. It isn't always how much light it puts out, it's where it locates the light. I've had Daniel Stern complain about the output of the basic Hella H4 hi/lo light - he says the internal bulb holder structure blocks way too much of the light from getting out of the housing. He likes the Cibie way more, and seems to know his stuff. You can email him and ask questions - he's been doing lights a long time.

http://www.danielsternlighting.com/tech/lights/lights.html

[LateFan]

These Cibie H4 high beams are really bright - most of the lens is just clear. I remember guys just putting 5 3/4" aircraft landing lights in for highs. Completely smooth clear lenses. Super bright, zero beam control!

[15Michaeljoseph]

These Cibie H4 high beams are really bright - most of the lens is just clear. I remember guys just putting 5 3/4" aircraft landing lights in for highs. Completely smooth clear lenses. Super bright, zero beam control!

[ATTACH]95754[/ATTACH]

i feel like 'plane light mod' would be pretty fun haha


--Mike

[Stanley Rockafella]

lol, I'd rock 'em!

[Stanley Rockafella]

[ATTACH]95753[/ATTACH]

where did you find this pic? are these available somewhere? seems like it has the citilight feature at the bottom too

[ELVA164]

I'd get in touch with user Mo Brighta (Andy), he's a good source of info and has helped me in the past.

[LateFan]

where did you find this pic? are these available somewhere? seems like it has the citilight feature at the bottom too

Oh...that's an old classic French Marshal you used to see in 911s or old Maseratis. 7". NLA, very rare. That insert is a high-powered high beam with a separate bulb.

[Mo Brighta]

Flat vs domed? Not the right question...

Oh...that's an old classic French Marshal you used to see in 911s or old Maseratis. 7". NLA, very rare. That insert is a high-powered high beam with a separate bulb.

Yeah, it is. I had a pair of them on my 2002 forever, that is until some ditz helped me break them by speeding up normally then stopping at the bottom of an on-ramp, right in front of me. Yeah, I know, my fault.

It is indeed French, a Marchal Amplilux. My brother gave me a pair on my 16th birthday to fit my first motor vehicle - a '62 VW Typ 1 (beetle) with a 6 V system, and yes, I found 6V lamps for it. What a difference it made over sealed beams! Not to mention the 1959 Porsche 1600 motor that made the wheels spin a little more briskly, but that's another story. Needless to say, the lights helped me see great distances at speed.

The Amplilux face was almost flat; very slightly domed, but that's not what made them good performers. It had much more to do with the reflector and the design of the lens rather than the degree of bulge. Some Cibie lights are actually are depressed a tad in the center, or concave. It's not the shape of the lens, it's the precision of the reflector shape, accuracy of the filament location within the reflector's focus, and the fluting in the lens that directs the light to the desired place on the road. That fluting is actually a sort of 'Fresnel' lens, also a French invention, a design which reduces weight and cost of very large lenses in Lighthouses, and can be found in the design of many BMW tail lights. The rear marker, or running light, usually has a clear one inserted behind the DOT retro-reflector (hexagonal prismatic reflector) and the red outer lens. That's why many older tail lights have no reflector; the Fresnel lens gathers and redirects the light as a focused beam to reinforce and amplify the light output very inexpensively.

If you look closely at an Amplilux (I have one that is apart), you will find they have a rather traditional dish that serves for the low beam (upper half), with a second dish in the bottom that serves as the high beam reflector. The low uses an H1, the high an H3 (with a short pigtail) for the luminaire. The high beam could be aimed independently of the low beam, rather clever for the day! And their design allowed both filaments to light at the same time on High, because they were physically separated by about 3 inches and by the metal of the smaller high beam reflector. THAT was clever! Naturally, I had rewired my 2002 with relays to take advantage of this, what a difference it made. As we know, many Euro cars were wired this way.

Now all that said, I prefer a flat over domed because flat lenses take headlight protection film much more easily. This is a big advantage after you spend Big Bux on a nice set of headlights. Which everyone should do if their car has sealed beams.

Holler if anyone wants pictures of my pair, one is minus the lens, the other is in a sort of semi-retired state with an older headlight film still holding it together.

[Mo Brighta]

Cibie high beam

These Cibie H4 high beams are really bright - most of the lens is just clear. I remember guys just putting 5 3/4" aircraft landing lights in for highs. Completely smooth clear lenses. Super bright, zero beam control!

[ATTACH]95754[/ATTACH]

Yes that is a nice light indeed. It uses an H1, not H4 - which is for High/ Low beams, as it has two filaments. The minor fluting in the lens shows there is 'some' beam control, but it's a High Beam, designed to throw light more widely than low beams. The entire lens is clear, what I think you mean is 'most of the lens is plain, with no fluting.'

That's the main reason I loved those Marchals; their design recognized low and high beams as doing very different jobs. Having two reflectors, two lamps, and two very different lens designs over each section allowed them to do both jobs well, excellent performance lights.