Comparison of Original and Halogen Bulbs

[MikeK]

In a recent thread LINK Mark Maron posted a picture of his new uber-spendy 6V halogen lamps from Classic Vintage Bulb. SteveB31 from Berts also posted a link to their 6V halogen. I put together three pictures:

Here's what I see-
1) Neither halogen has the same filament shape or orientation.
2) One halogen will permit some light directly to the lens, one only permits reflected light to the lens.
3) One halogen bulb has the filament focal height of both the low and high closely grouped, one has them spaced far apart.
4) The center bulb could be brought to the original focus height if the lamp socket can be extended much farther forward- Can it???
5) The far left bulb was clearly designed for a purpose-engineered modern bi-focus reflector with a clear lens cover. Note the low beam reflector and different focal distances of the two filaments. Will it produce a usable beam pattern with the straight parabolic dish A reflector and Ford's purpose-engineered Twolite lens???

 

[Mike V. Florida]

Interesting.

 

[duffer]

We need more guys like you around here...great work...thanks.

 

[Kurt in NJ]

My camera won't do as good for pictures of a bulb ---this is classic and vintage 35/50 for 6V generator use

 

[Kurt in NJ]

I tried a different setup

 

[Pat Martone]

MikeK,
Thank you for your great posting showing the physical differences between the original and after market halogen bulbs. Your illustrations are outstanding.
I provide my experience here just as an FYI; your results may vary.
I am running 12v and an alternator, and also have the latest made-to-ford print headlight reflectors that I got from Bratton's last summer.
I tried using the halogen bulb illustrated in your second photo, but could not focus the beam. Thinking that I must not know what I am doing since many people tout the great benefits of these halogen bulbs, I also had one of my club member's try to focus the beam in his fully instrumented Model A garage set-up for headlight alignment. Unfortunately, he also could not get a good focus, so I switched back to the original type bulb. Of course I was disappointed that I could not get these expensive halogen bulbs to function properly for me. I will say that I could not detect (with the naked eye) a significant (or any) brightness difference between the original type 12v 50/50 bulb and the halogen bulb.
I truly hope that others will have better results than I did.

 

[2manycars]

I had a halogen setup in my roadster for a while. The lights were very bright, but I could not get them to focus. The result was that while the countryside was well illuminated, the road was not, except near the car, and the oncoming traffic was blinded and annoyed. I replaced the setup with original re coated reflectors, and 50-50 bulbs, and the result was very satisfactory.
All modern "improvements" are not an improvement.

 

[BRENT in 10-uh-C]

I like what Mike is saying and I would like to expound on the latter part of his #5 point. I think we would all agree there is a huge difference between the correct shaped reflector vs. incorrect aftermarket reflector, ...AND there is a huge difference between dull silvering, incorrect plating (chrome), and correct silver plating as far as light reflectivity is concerned. So, if the reflector is such a vital part of having adequate lighting, what does this mean as far as the light bulb is concerned?

Another question is if we use any of the light bulbs as shown above with a properly silver plated original reflector, is the reflector responsible for 50% of the total lighting output as seen 10' in front of the bulb, --or less percentage --or more percentage? My thoughts are more.


One other point that has always been explained to me is lumens (or candlepower as expressed in headlight bulb ratings) are the same measurement whether it be from an incandescent bulb or a halogen bulb. The difference with halogen bulbs are they produce more lumens than a 32/50 candlepower bulb. Therefore they ARE going to be brighter. Place the same candlepower incandescent bulb in place of the halogen and it will be the same brightness. That is why there is such a difference of opinion as to whether halogens are better. To some halogens are brighter so they feel they can see better while others place more emphasis on the reflector so they can see better.

 

[MikeK]

I've added the photo from Kurt. Although this 6V 35/50W lamp is touted as "generator operation", a pair will draw ~16amps on high beam. Add 3A for ignition and 2A for tails and you are well over the sustained running limit of 17A for an A genny. Got replacement smoke?

 

[Kurt in NJ]

I tried again for better pictures, and took out the 12+ year old 35/35 bulbs --they are 1- 5/16 pin to filament ---the focus point was very close to the Mazda bulbs I had before (I will look for them)

I have been thinking of setting up a headlight and trying different bulbs against an old 30s headlight aiming board that has a meter, it is the same machine that NJ state inspection used for many years ---it is becoming obvious that there are many different interpretations in making halogen replacement bulbs.

the 2 top left and center are better pic of the 35/50, the right and bottom left are my old 35/35

 

[Kevin in NJ]

You have to include one more parameter.

The relationship of the filament to the pins. I believe the filament has to be horizontal as part of how the system works.

 

[jrelliott]

Another reason Halogen bulbs appear brighter is they produce a wavelength of light that is closer to blue than incadescent bulbs

 

[msmaron]

For those that did not see the candle power in my last post...also should be noted these bulbs are the EXACT same price as Berts, Brattons, and all the rest. They all have shipping attached to them. The difference is that these are 60/55

2w=3cp
6w=6cp
10w=-15cp
16w=21cp
25w=32cp
35w=50cp

so 60w=82cp if i am correct....

 

[msmaron]

Mike the comparison is outstanding..But you state what you "SEE"...do you have an opinion based on comparison?
I have not installed them as of yet or attempted to focus them, that will be the real test but was wondering your "opinion" on what you have seen by comparison.

 

[MikeK]

Another question is if we use any of the light bulbs as shown above with a properly silver plated original reflector, is the reflector responsible for 50% of the total lighting output as seen 10' in front of the bulb, --or less percentage --or more percentage? My thoughts are more.

Here's one way to figure the %. Refer to the diagram below.

Measure the distance from the filament to the edge of the reflector. This is the RADIUS.
Measure the angle from the center line @focal point to the reflector edge. This is THETA.
Compute the surface area of the sphere of total photon emission, outlined by the red circle. A = 4pi x r x r
Compute the surface area of the cone of unreflected photon emission, shown in yellow. A = 2pi x r x r (1- cosine theta)
Use the two areas to calculate either the direct or reflected %. (simple arithmetic!)

Side note here:
1) Not all of the light that flares through the lens (blue) without parallel reflection is bad! All of the scatter light below the centerline is useful road illumination. You may consider using 1/2 the area of the unreflected cone of emission when figuring % of useful light.

2) The 60/55W lamps with the BLOCKED forward emission eliminates much of the unfocused forward scatter, but does not reflect that light back to the reflector. The black top converts visible photons to heat. Is this good or bad? You eliminate the annoying upward scatter that illuminates trees, but you also lose the useful down-scatter that illuminates ground close to the vehicle. On a positive note, there will be less glare to oncoming traffic. The low beam filament internal reflector will bias which section of the Twolite lens receives the most light. Result unknown without field test comparisons.

 

[H. L. Chauvin]

Thanks for sharing -- very well illustrated.

Appears down range focusing on a distant wall, (as indicated in the "Model A Owner's Manual"), would give a very detailed analysis of what one could expect from each bulb indicated using an original Ford silver plated headlight reflector.

Then, if one wanted to get a bit more technical, to document metered light intensity, one could maybe borrow a light meter from an electrical engineer or sports lighting contractor who is hired to re-direct lights on football & baseball fields.

Analysis appears similar to one fine tuning & adjusting the choke on a shotgun barrel with calipers & a fine stone hone; i.e., one never knows exactly what pattern one can expect until a target is provided downrange & one pulls the trigger.

Most interesting subject!

 

[P.S.]

Good point.

I happen to be an electrical engineer, and would be glad to make the comparisons and measurements.

Anyone want to donate a set of original 30-31 reflectors with lamps? I can swap my modified halogen reflectors out for the stock ones easily as I retained the bullet style connectors in the buckets. The test could be made on the same car with same electrical system etc. which would be much more accurate than 2 separate cars.

 

[msmaron]

2) The 60/55W lamps with the BLOCKED forward emission eliminates much of the unfocused forward scatter, but does not reflect that light back to the reflector. The black top converts visible photons to heat. Is this good or bad? You eliminate the annoying upward scatter that illuminates trees, but you also lose the useful down-scatter that illuminates ground close to the vehicle. On a positive note, there will be less glare to oncoming traffic. The low beam filament internal reflector will bias which section of the Twolite lens receives the most light. Result unknown without field test comparisons.

Basically if i read what you are saying is that This bulb in particular will NOT focus the ford way due to the "Blocked" Shield on the bulb and will have a tendency to give me more UP ward, side and downward light.. All of course subject to change until i test them

 

[MikeK]

You have to include one more parameter.

The relationship of the filament to the pins. I believe the filament has to be horizontal as part of how the system works.

Good point. One that I did not want to address, but. . .
A paraboilc reflector has a single infinitely small focal POINT. Any filament will have physical dimension, larger than a point. The farther from that point, the greater the reflected deviation from parallel. The original lamps had the filament in a "V" shape to keep them as compact as possible and close to the ideal focal POINT.

The axis of filament deviation from the focal point (orientation and shape of the filament) will produce a specific summary set of off-axis photons. The Twolite lens was designed with multiple sub-lenses or lensettes to maximize refocus to the desired road pattern using the original filament shapes. Of note here, the tiny vertical separation distance between the Hi & Lo filaments of an original bulb will bias the deviation from parallel reflection slightly up/down.

As to whether a vertical, horizontal, or axially linear (straight forward, like the 55/60W) filament will produce a better or worse road pattern through the Twolite lens can only be determined by ray-trace geometry or field test.

To add insult to injury, NOT ALL TWOLITE LENSES FOCUS THE SAME. There was a barely perceptible change in some of the lens elements as Ford went from 21/21cp. to brighter bulbs in later years. I'm sure some of this change was to further refine the road pattern, too. The J.S. DO NOT address correctness of lenses in this way. Here are some pix from my lens collection to illustrate the point. ALL FOUR of the pictures have a different center element as well as other changes:

 

[MikeK]

Basically if i read what you are saying is that This bulb in particular will NOT focus the ford way due to the "Blocked" Shield on the bulb and will have a tendency to give me more UP ward, side and downward light.. All of course subject to change until i test them

Just the opposite. You are blocking direct off-axis flare emission. You may be very happy. I make no assumptions. (Been there, done that!)