Does anyone know what the true measurements across the face of the various PLM's are?
Measuring the arc across the back these things really gives me no idea how big they really are.
Kacey wrote:
Does anyone know what the true measurements across the face of the various PLM's are?
Measuring the arc across the back these things really gives me no idea how big they really are.
As I mentioned on POTN, Jerry, my 51" PLM V2 actually measures 43" across the face. Measuring around the back makes no sense at all. Using that approach, an Elinchrom 39" octa and 39" deep octa could be marketed as 47" and 60" respectively and in neither case would the buyer have an accurate indication of what he was buying. I'd like to see umbrellas spec'ed with diameter across the face and aspect ratio (e.g. diameter/depth).
Every umbrella that i've ever bought is measured across the arc. (photoflex, lastolite, lowell tota and westcott)
It is inconvenient but I can see why a manufacturer would do it. To be fair Alien Bee's site does show both the arc and diameter on it's umbrella description. I think photek size theirs accross the front points. Even measuring across the points will add almost 1.5 " over the fabric diameter.
Still, this is an energy quantity, not an amount of light. It assumes that all systems have the same efficiency, which is not true.
Which is why they tried guide numbers. Truth is that most manufacturers will game whatever spec anyone comes up with to make their stuff look as good as possible. In reality the small differences in actual light output are not that significant. You get a system, you work with it to get used to it. Cracks me up when I see people getting all worked up about these things. There are reasons we still use light meters - it measures what is actually being delivered at the time.
Kacey wrote:
Does anyone know what the true measurements across the face of the various PLM's are?...
One more data point for you, Jerry: I received my 64" PLM yesterday. Actual diameter is 55". It would seem, then, the "Buff Constant" is approximately .855.
Still, this is an energy quantity, not an amount of light. It assumes that all systems have the same efficiency, which is not true.
WS is Watt*Siemens, because S is the official symbol for the unit of electric conductance. The only correct units are J (Joule), W*s (Watt times seconds) or Ws (Wattseconds, just an abbreviation of W*s). A capital S is something entirely different than a lowercase s.
One might as well say '400 pig noses', because everyone knows what's meant in a discussion about monolights. It still hurts me to see such an abuse done to SI units.
Which is why they tried guide numbers. Truth is that most manufacturers will game whatever spec anyone comes up with to make their stuff look as good as possible. In reality the small differences in actual light output are not that significant. You get a system, you work with it to get used to it. Cracks me up when I see people getting all worked up about these things. There are reasons we still use light meters - it measures what is actually being delivered at the time.
Lumens sans reflector works, but few manufacturers provide it.
The cine industry demands real numbers and gets them time after time, but the rest of us in other photography feilds are too lazy and non-vocal about it, so we get fed a wide variety of "standards" that manufactuers of all types come up with.
Who should we blame, the manufacturers for serving what most of us are happy to swallow, or us consumers for being willing to swallow it?
PS I still can't beleive Kodak got away for so many years with rating their print longevity based on testing behind UV glass at brightness levels many of us would have trouble reading a newspaper in.
PPS I haven't checked recently, Kodak may still be quoting based on these same "standards."
Tobi. wrote:
WS is Watt*Siemens, because S is the official symbol for the unit of electric conductance. The only correct units are J (Joule), W*s (Watt times seconds) or Ws (Wattseconds, just an abbreviation of W*s). A capital S is something entirely different than a lowercase s.
One might as well say '400 pig noses', because everyone knows what's meant in a discussion about monolights. It still hurts me to see such an abuse done to SI units.
Tobi, nitpicking.
Capital S vs. s depends upon where you got your "official" acronym. Mine came from my 1st engineering job.
In the USA, we don't use Siemens as a unit. The symbol for conductance that we use is mho which is an upside Omega that is equal to 1/ohms.
Quite simply, a resistive load, such as a light bulb, having a 1000W rating, may also be rated at 1000 w/s (watts per second). If this load is operated for 1/10 s, 100WS, or 100 Joules are dissipated. Watts defines a "rate of energy use", WS or Joules define an "amount on energy". In water analogy, a gallon is an amount while gallons per second is a rate.
The D-Lite 2 is actually $274.89. The prices have dropped since you did that comparison, Mr. Buff. Also the new D-Lite has built-in receiver on top of being cheaper than the previous model.
There might be other stuff as well that might be different on the new one than what's stated on your old test results (Feb. 2007).
