SF P61 vs P60 LUX measurements

This is kind of unexpected- I just got my USA Ltd edition 6P Surefire in, and I had ordered a P61 lamp assembly to go with it- Supposedly the P61 lamp assembly is 120 Lumens compared to 65 Lumens for the standard P60 Lamp assembly.

I was just starting a test where I was going to measure all of my factory flashlights on my cheapie LX-101 LUX meter to have a standard of measurement for comparison for my mods and other factory lights.

Anyway, Testing in the same body with the same batteries at one meter, the P60 gives a higher LUX reading than the P61; I did the testing three times, in a different order so that battery drain would sort of be equalized, and every time the P60 actually read brighter by about 250 LUX than the P61.

(Both ranging between 3730 to 4230 LUX @ 1 meter)

(Both lamps are off scale with the light in contact with the meter sensor, so I can't get an estimate of total light output with this setup- I guess I could use some ND Filters between the light and the sensor to cut down the light so that it would be on scale, but I don't have any handy.)

Now admittedly the P61 does have a "hot spot" about 2.5 - 3 times wider than the P60 at about 6 ft, but I was really expecting that the P61 would have a brighter max reading and a farther "throw".....

OK, I just went outside, and while it isn't quite dark out there, I compared the "throw" and the P60 seems to go about 15-25% farther than the P61, although the P61 still lights up a 2-3 times larger area.

I was hoping more for "throw" than area lighting with the P61, and looking at the reflectors, there does seem to be a difference in the elipse or parabola of the two.

Maybe I need to use the reflector from the P60 on the P61 bulb to get the "throw" I want.

Any ideas or comments?

I think you're confirming what I've heard about Surefire HOLAs--and I could be wrong on this, but look at Brock's numbers, too--that the higher output (lumens) assemblies cover a larger area at the same intensity.

Your measurements in lux at one meter, by the way, are directly convertible to Craigs and my peak candela measurements. one lux at one meter equals one candela.

Cheers,

Richard

When I bought my M2, I was expecting to get a longer throw out of the P61, Wrong! Since I mostly use my Surefire's for long distance
illumination, I traded the P61 for a P60. Then I sent my M2 in on warranty, and I came back with a P61 in it! Just when I thought I was rid of the P61 it shows up again! I posted about it in the buy\sell\trade portion of this forum, but I have gotten no response, so if anyone reads this, and wants
a P61, fire me off an E-mail, and we'll work out a deal!

Yep I have to agree. Of the surefire's I own the only HOLA that really impressed me is my P91 and from the beam shots I've seen mine is a fluke and just abnormally tight. I think the common mistake made is that the high output lamps put more light in the same beam size (I know that's what I expected) and it does not work out that way. Which is probably why in general I stay with the normal output lamps. I'd rather have 3 times the runtime than a beam twice as large and only slightly brighter.

My M3 the hot spot on the 225 lumen bulb is a little brighter but mostly it's just a larger beam with similar brightness.

Same with the P61's I've seen slightly brighter hotspot, but mostly just a larger beam area.

This is where lumens can be just as confusing as candlepower. The bulbs put out aprox. 2x the lumens but that doesn't equal two times as bright unless the beam angle is the same for both lamps. With the surefires anyway that is not the case.

I'd guess it just comes back to that surefire makes turboheads and they figure if you want a tighter beam you will get a turbohead. For me anyway the turbohead lights throw a great beam but are just not practical for everyday carry. On the plus side thier beam size works for probably 90% of my use.

Tis true, the P61 and P91 are very close in peak CP output, they just light up a larger area. I would really like to see them focus the P61 to the same beam size as the P60, now that would kick out some serious light!

Thanks for your input everyone-

Has anyone actually dis-assembled the P60 or P61 lamp assemblies?

As long as the filaments in their respective bulbs are in about the same positions, I would imagine that putting the P60 reflector on the P61 bulb would result in the "throw" that a lot of us were hoping for.

It *LOOKS* like the reflectors are just glued on, and it may be pretty easy to swap the reflectors. I'll go ahead and give it a try in the near future and report the results here.

But if anyone has "Pioneered" in this respect, and can report any useful information and save me some time or money, I'd really appreciate it.

Thanks!

I did just hack up a P60 bulb. I'm not sure it would be possible to get one apart without hurting it. The epoxy they use must be a very high temp and the bulb housing has a post that goes into the AL reflector. So even if you cut through the epoxy on the outside if they have epoxy on that post it would have to be cut through or broke off to remove the bulb assembly.

It would be interesting though. I hacked up a old P60 bulb that burnt out and refitted it with a scorpion bulb. While it was not a success in that it's about the same light output and the bulb only lasts for 3-5 hours what I was interested in is if it would be possible to get a tighter beam out of the reflector. That was a success I was able to get about half the beam size of the stock P60 bulb by moving the bulb forward slightly and it kept it's smoothness. It did loose quite a bit of the surrounding light, as was expected.

If I had a spare M3 bezel sitting around I'd try milling down the reflector end a little in order to bring the bulb forward in tiny incriments in order to see if it could be tightened up as well. My guess is it could be significantly tighter without needing a turbohead. However, I wouldn't want to ruin my only bezel to find out I was wrong

Todd

The reason (or so I have been told) the P61 has a larger spot is because the filament is larger, about 2.5 to 3 times larger, so the spot it reflects out is larger. I do think they could reshape the reflector to a tighter focus, but that would mean retooling the reflectors, as far as I can tell they just use one and then have different lamps that go in them.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by ToddM:
... This is where lumens can be just as confusing as candlepower. The bulbs put out aprox. 2x the lumens but that doesn't equal two times as bright unless the beam angle is the same for both lamps. With the surefires anyway that is not the case.
...<HR></BLOCKQUOTE>

Todd, the Lumens are twice as much, so the overall output is really twice as bright. If you tried to use CP measurements to relate the beams, it still wouldn't be of any use.
As you say, in this discussion, a beam distribution ratio is essential to get the difference. I think I'm just repeating what you've said actually, but I'm certain that Lu almost always has a relevance that CP just doesn't.

Silviron,
I've successfully removed a P60 lamp leaving both lamp+base and reflector in one piece and still workable. This was about 3 months ago, so from a fairly recent batch of P60's.
It wasn't *too* difficult.

The P61 is made differently, and not worth trying without serious equipment, preferably in the factory it came from. You can be left with the reflector in good condition, but the lamp will be wrecked.

lightlover

I really think that both lm and cd are important measures.

In fact, a polar plot of cd would be the most useful of all (done in H and V axes). This is done (in essence) for microphones, speakers, and luminaires.

The total lumen output is useful to know, but doesn't show how much light is in the beam. Calibrated beamshots and peak candela are another good way to go. Hey, that's what Craig is doing with the Prometrics box!

I don't think total lumens alone tells you much about the beam. You could get all those lumens from an household-type A lamp with no optics, but that wouldn't help much with what goes bump in the night outside your window. After all, a 40W GE Soft White A lamp puts out 490 lumens but only (theoretically) 40 candela (490/(4*pi) if it's an isotropic radiator (well, it doesn't put any light out at its base...) But it's 40 candela is (theoretically) emitted in all directions.

Cheers,

Richard

Personally I see little use for lumens or candlepower without a beam angle rating or beam shot. Brock's site does the best job of this so far, and it's what's needed to really get a good idea how the light performs. Especially in comparisons.

Lumens is great, it's how much light you have but it tells you nothing about the intensity of the light in any one spot. A 60 watt bulb has almost 1000 lumens but you wouldn't want to try and light up a object with it at 50 yards without a relflector.

My issue with lumens is people make the mistake of a bulb with twice the lumens being a similar beam shape being twice as bright. That's not true in the surefire case because the beam size is not the same. It's slightly brighter (as brock's candlepower intensities confirm) but the beam angle is almost twice the lower power lamps. This does result in more "volume" of light, but not light with twice the intensity in the hot spot.

Candlepower is bad too, it's more manipulated than lumens cause frankly most companies use candlepower (probably cause it's a bigger and more impressive number). It has problems as well it will tell you how bright one tiny part of the beam is but not the overall shape or overall light output. If you have a tiny pencil beam with no flood light you can have a huge candlepower but have a nearly useless light (IE a maglite on it's tightest spot). Lot of candlepower but when you only have a 4" circle of light at 20' it's use is limited as well.

So IMO without beam angle and composition information both lumens and candlepower ratings are really not very helpful. Which probably means that unless companies start rating bulbs with candelpower, lumens, and beam angles (like that will happen) all the lumen and candlepower ratings are really useless.

Todd I couldn't have said it better myself.