[MF3D.FORUM:1476] Re: NSA MF slide show

["Bill Glickman" <bglick@xxxxxxxx>]

David

> > not many people can fire 300 Gn flash, even a $1k
> > top of the line Metz only offers about 145 GN.
>
> I am starting to see many flashes with a "rated" GN of 160-180
> in feet with ASA 100. I quoted rated as many manufacturers
> highly over-rate their flashes. I highly recommend that anyone
> using a flash determine the actual GN with the
> camera/film/subject set up they use.

             Yes, overstate, is the key word here....what they do is rate
their flashes not at the normal fl lens, but 2x the normal, then up the
guide number by 25%... this is a game the makers are playing...I have not
seen any portable flashes that exceed 150 gn for normal fl lenses!   Even my
big huge qunatum is only 160, and it is huge and heavy and so is the battery
pack!   But it fires fast, like every 2 seconds...

> I use a slave made specifically for cave photography. It is
> called the Firefly and is made in England by cavers. It uses
> IR cutoff as a trigger so random light flashes from caving
> lights won't set it off. It is also good out to about 1500
> feet and works around corners. Most of the light slaves (like
> the Wien) need direct line of site and are good for only a
> couple hundred feet. The other problem is that most light
> slave will not be fired by flashbulbs. I do have one Vivitar
> 283 with a permanent Wien slave foot. I use this quite a bit
> for simple fill flash.

            Wien and Quantum also make the IR system here in USA...they
require additional purchase of the transmitter, they work quite well, I have
used them.  But now, if anyone is ever interested in this, the new LPA
design uses FM transmitters which are impervious to anything, even walls!
They are not that expensive and have performed flawless in the past 1.5
years.   Also, as for Wien flash detector ones.... I have experimented with
all of theirs, and David you are right for their lower end units, but there
top end unit, for about $90 called XL I beleive is truly remarkable... I
have fired flashes in areas I never dreamed in a million years that the
slave would see it, and it did every single time...but with our eyes you can
not see the flash, thats how sensitive it is!   But this is not true of the
their lower priced models.  The reason I use the FM more now is that these
Weins can be so sensitive, even changes in sunlight can make them go off!
Not true for the FM receivers....   I never heard of the ones you are using,
but will look out for them....  flash can be so critical for stereo
photography since the chrome films have such limited exposure lattitude.....

> The pf300 will give a GN of 550 with an ASA of 80-125 and a
> shutter speed of 1/30th or less. They also have a pf330 bulb
> that is so powerful they don't have a GN for it. It is used
> mainly in high speed motion picture photography.

        I think the electronic flashes make more sense, specially if you
already have them...but if you don't use them often, this flash bulb idea is
great!  But a good flash meter would be nice...

> At $50.00 each you had really better be sure everything is set
> up right. I don't think you would want to do too much
> bracketting in a scene that used two or hree of these *{;-)

      Ouch!!!

> > I just carry 6
> > flashes with me and put them around the scene...
>
> That is the best approach. Just make sure to get the right
> distance from flash to subject so all the flashes are balanced
> to the same fstop. or use a flash with variable power settings
> or an auto setting.

       yes, I adjust each flash accordingly...this make it very versatile
system...

You can also use one flash and pop it off
> multiple times, but then you have to do all this math to know
> just how many times to fire. A flash with a GN of 100 flashed
> twice does NOT give a GN of 200!

       I will have to research this again.....you could be right...what
formula do you suggest?

Bill

>
> David W. Kesner
> Boise, Idaho, USA
> drdave@xxxxxxxxxx
>