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Old July 16th, 2003, 08:05 PM   #1
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Is is possible?

I got an Arri 300 fresnel recently. I also have a B&M 650w fresnel. when I got the Arri 300, I did a test, and I'll be danged if they didn't look like they had about the same brightness and amount of spot/flood coverage. Shouldn't my 650 be twice as bright as the Arri? B&M is an older company -- none of you answered an older thread I posted regarding them, so I'm guessing none of you have heard of them, either. I did also get the 650w on Ebay, through Pyramid films, while the Arri was new from B&H. Bulbs don't get dimmer as they age, they just die abruptly, right? But it should have been a new bulb in the 650 anyway.

I did a test with my camera, as well, not just my eye. With the lights set at the same distance from a slightly off white wall, and set to approximately the same spot/flood setting, I was able to achieve correct exposure for the arri 300 at f3.2, and the 650w at f3.4. This is not much difference. Camera's zebra bars were set to 100 IRE.

What is the cause of this? The age of the technology of the B&M 650? Did I put the bulb in wrong? Am I semi- or completely retarded? I know wattage is not a measure of brightness, but rather of how much electricity something draws when it operates, but I figure a 300's a 300 and a 1k is a 1k, no matter who makes it (unless it's a worklight from Home Depot).
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Old July 16th, 2003, 08:21 PM   #2
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It'd be helpful to take a look at the photometric data of the two fixtures, the arri is obviously easy to find, its on their website for all to see...but do you have this for the B&M? Wattage often does not alone dictate how bright something is...other factors are involved.
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Old July 16th, 2003, 10:03 PM   #3
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Josh,
Casey's right. Raw wattage does not tell the entire story. With fresnels, in particular, the quality and nature of the lens makes a big difference in how efficiently light is focused.
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Old July 17th, 2003, 01:26 AM   #4
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They have specs on their website

http://www.bmlighting.com/catalog/babymacspecs.htm

It's the baby mac 650
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Old July 17th, 2003, 09:44 AM   #5
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There are plenty of factors, but today's new lamp designs are MUCH
better than those of yesteryear. An HPL 575W lamp, like those used in
ETC Source 4 fixtures, put out more actual light than a 1000W par.
Even 1000W par lamps vary depending on whether it is a narrow, very narrow
med. wide flood, etc.

A 400W HMI will put out something like 4X the amount of light as a tungsten
lamp of the same wattage AND daylight color temperature at the same time
(whereas if you have to gel a tungsten/halogen lamp to 5600K,
you lose at least 50%. That's one reason why HMI cost 10X more).

In addition to different lamps producing differing lumen values, today's
computer designed mirror/reflector technology is also further advanced
than old school stuff allowing for higher output.

Although there are many factors, it pays to do some careful research,
and as is usually the case, you get what you pay for.

You also asked about old lamps getting dimmer . . . they do, especially HMI.
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Old July 17th, 2003, 11:03 AM   #6
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This company, B&M is still in business, however. Wouldn't their stuff need to be updated to keep up with the competition?
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Old July 17th, 2003, 12:07 PM   #7
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<<<-This company, B&M is still in business, however. Wouldn't their stuff need to be updated to keep up with the competition? -->>>

Before judgement can be passed, you have to check and see what lamps
you have in those fixtures. Only Arri published a 'photometric table', so
maybe B&M is hiding something.

From the B&M website, there are two flavors that work in those 300W Fresnels.
One is a FKW which takes more power
(2.5 amps and probably puts out more light, though some lamps have a
thicker element and therefore last longer, but output less lumens)
and the other is a FSK which draws only 1.2 amps.

From the Arri site, they use the FKW lamp.

So, there could be a couple of things that make the difference in your test.
1) a- How wide the beam is set . . . spotted, flooded, or in between?
b- How far the fixtures were from your target (inverse square law)
2) Which lamp is used (this is a biggie)
3) Mirror technology used by each company (I mentioned that earlier).
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Old July 17th, 2003, 01:33 PM   #8
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Like I said, the tests were performed with everything identical on both lamps - distance from target, spot/flood setting/ etc. The lamp could be a variable. I don't know what I put in. . .it was what they gave me. I'll email and ask.
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Old July 19th, 2003, 01:00 AM   #9
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It's a 650 w lamp--frk according to the guy. I compared the photometric data on both companies' sites, and unless footcandles is like golf where you do better the lower the number, than my 650w should far outperform the arri in terms of the footcandles at a certain distance from a target at a given spot/flood setting.
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Old July 19th, 2003, 10:12 AM   #10
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Interesting. According to the Arri site, the FRK does 5861 lumens @ 3 meters.
The lamp used in the 300 arri, the FKW does 1870. So the FRK should
be about 150% brighter.

A couple of things I noticed. There is a big sale on the mac lite 650.
Maybe they are about to update a fixture long overdue.
When I clicked on the zoomed image of the B&M, the fresnel lens
looks like it has a lot of diffusion built in and seems to have far
fewer steps in it than the Desisti fresnel lens we use at the U.
Those factors coupled with an inefficient mirror could easily be
the difference.
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Old July 19th, 2003, 10:35 AM   #11
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Sigh. . .probably. By "steps" you mean the ripples? I'll do a by-eye comparison just for funsies to see how differently they're built.
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Old July 20th, 2003, 12:39 AM   #12
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Did my unscientific comparison. I swear the reflector and the lens looks the same to my eye--the "bowl" of the reflector is the same size in both lights, and the texture on the glass of the lenses is the same--the arri has more ripples, rings, steps, in the lens--maybe three more than the B&M.
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Old July 20th, 2003, 12:52 PM   #13
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Hey Josh,

I would guess that about the only thing that is still unknown and
possibly the reason for the 650W being no brighter than the 300W,
would be the type of lamp. In the HPL series of lamps, they make
high lumen/short life and long life/lower lumen. There is a big
difference between the two in output. Maybe this series of
lamp also?

Other than that, the next level on inquiry would be to run completely scientific tests. That's nothing either one of us wants to personally
undertake ;)

Hey, what about trying to put the lamp from the 300 into the 650?
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Old July 20th, 2003, 04:38 PM   #14
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I'll look on the lamp and see what it says. I'll try your test too. . .what am I trying to learn by putting the 300w bulb in the 650?
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