[Konvas] lighting pars vs. fresnels (off topic)

[FauxFilm at aol.com]

PARS are considered to be a little bit more efficient than fresnels, and  are 
generally a bit lighter in weight and smaller in size than equivalent  
fresnels, too.
 
I use both fresnel and PAR HMIs and there are advantages and disadvantages  
to both.  I would say the upside of fresnels is the ease of focusability...  
just turn a knob and you can go from spot to flood or anywhere in between.   
With PARS you have to swap lenses, which can be a bit of a pain in the rear,  
especially if the instrument is already hot or the face of it is in a difficult  
to access location.  PARS often also have a "focusing knob" that slides the  
globe in and out, but it controls light OUTPUT a lot more than it does much for 
 focus (you don't have to use wire scrims on them quite so much)... you still 
 need the lenses to define the beam spread (and to block the considerable 
amount  of UV).
 
And as I said, there is the size/weight factor, with PARS generally being a  
bit smaller and lighter in weight.  There are exceptions (the Strand 1200w  
PAR HMI we sometimes use is HUGE and heavy), but generally not.  The 800w  
Joker-Bug HMI is TINY (with a VERY small and lightweight ballast) and it is so  
efficient that it puts out almost the same output as a 1200w HMI fresnel.   The 
downside of the Jokers is cost...  the 800w is about $6500.
 
In the HMI world, PARs seem to be most prevalent in the mid-range  area....   
from 150w to 800w you see mostly fresnels....  from  800w to 2.5K you'll see 
a mixture of both PARs and fresnels... and anything  bigger than that are 
usually fresnels.   Not sure why exactly, but  that's just the way it seems to be.
 
You pose an interesting question... I've never seen a tungsten PAR (at  least 
not one built the way HMI PARs are, with the moveable bulb and  
interchangeable lenses) but they might exist somewhere... there's no reason why  they 
wouldn't work.   Smith Victor makes a very cheap (<$100)  little 650w tungsten PAR 
that we have a couple of... it has a focusing lever  that moves the bulb in 
and out a bit, but the amount that it changes focus is  actually very VERY 
minimal.  No lenses for that instrument.
 
As an aside, I did recently build my own homemade 150w HMI.  I needed  a 
little instrument that was small and lightweight enough to just hang on a grip  
arm on a C-stand to use as a backlight/hairlight....  and anything  commercially 
available was way too heavy.  So I took a cheap and very  lightweight PAR 38 
can (like DJs use) and fitted it with the proper socket for a  150w HMI globe, 
reflector, sheet metal heat baffles, a fresnel lens in front,  and a 
reasonably long cable that plugs into the ballast.  It won't focus  (the beam is set 
at medium-wide) because there wasn't enough room inside the  housing for the 
mechanics, but it is extremely small and lightweight, which was  my goal...and 
with great output.  It's pretty efficient, probably the  equivalent to about a  
650w tungsten... maybe more (but 5600K daylight, of  course).   It was also 
only a few hundred bucks to build, which in the  HMI world is peanuts.  Here's 
what it looks like size-comparison-wise next  to a 1200w HMI fresnel (and the 
1200 in the pic is a compact, not the bigger  ones):  
_http://fantasticplastic.com/diy/hmi05.jpg_ (http://fantasticplastic.com/diy/hmi05.jpg) 
 
T2
 
_____________________________________________
Todd Terry
Creative Director
Fantastic Plastic Entertainment, Inc.
_http://fantasticplasticcom_ (http://fantasticplasticcom/) 
 
 
 




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