Film-Tech Forum ARCHIVE: Super Lume X Reflectors

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Posted by Don Furr (Member # 1469) on 03-11-2010, 08:26 PM:

I'm running a Super Lume X lamphouse in my screening room. I picked up another lamp for a spare. One has the silver reflector and the other has the yellow reflector.
Which reflector is preferred?

Posted by Gordon McLeod (Member # 33) on 03-11-2010, 09:36 PM:

The silver reflector is a "hot" rhodnium one the yellowish one is a cold dichroic who's colour temp will be writen on the back

Posted by Don Furr (Member # 1469) on 03-12-2010, 06:21 AM:

Thanks Gordy. This one has 5400 written on the back. Using a 1600 bulb which one should I be using?

Posted by Mark Gulbrandsen (Member # 72) on 03-12-2010, 08:06 AM:

I'd prefer the silvery rhodium version... The light is closer to sun light and not as cold of light as the dichroic would be. That said the whole setup will also run ALOT hotter! You may experience shorter lamp life as well as a much hotter running gate even with the 1600 watt lamp unless you add a heat filter in the front end of the lamphouse. Note that even ORC 1000s had heat filters!!

Posted by Dave Macaulay (Member # 813) on 03-12-2010, 08:23 AM:

Use whatever looks best to you, the silver one is probably a dichroic with few hours on it from a lower wattage lamp so that it hasn't turned yellow yet.
Rhodium reflectors are fairly rare, and some coated reflectors look quite silvery. Both are a stamped metal form or an electroplated nickel form with either a bare rhodium metal plating or a dichroic coating to absorb some infrared energy. Rhodium coated mirrors have a very uniform effect on the lamphouse's colour temperature, the dichroic coating is not very uniform that way and the colour shift varies widely. There's a LOT more infrared heat energy in the light beam from a rhodium plated reflector, so for even small power lamps you may need a heat filter at the least... which is another dichroic coated element with the same variability in colour shift.
Absolute colour temperature is only an issue for studio and lab screening rooms (and possibly a few oddball venues) but is routinely ignored in all platter based commercial cinemas. The few remaining changeover screens should have somewhat matched colour temperatures but nowadays I don't think many techs even look for colour changes on changeovers.
My point, should I have one here somewhere, is that I doubt you have a rhodium reflector. Strong (actually their supplier) measures colour temperature of the coating and codes the reflectors accordingly. Some have an actual number, most have a three letter code like BBD that converts to colour temperature. I don't have the code here but it doesn't matter for a single projector setup, preferably the codes should have the first two letters the same for a changeover setup. If you see such a code on your silver mirror then it is not a rhodium plated mirror. The part number is also different for rhodium ones, and that should be handwritten on the back of the bowl. I don't have this number and it isn't in the Strong price list - showing how unusual it is to find one?
The heat load on the trap and the film itself is much higher with a rhodium reflector. Even with 1500W you will get a very hot trap and may want a heat filter glass in the light path.
The colour temperature with rhodium isn't better than from a dichroic reflector, it is just more consistent. A studio or lab screening room needs (wants?) consistent colour temperature on screen, both projectors and over an extended time. Getting either matched reflectors or heat filters is a major PITA. Setting up the room with rhodium reflectors than matching the heat filters and lenses as well as possible then doing final colour temperature correcting with filters in front of the lenses means a lamp explosion just means a new rhodium reflector and minimal downtime. Using dichroic reflectors would mean an extended closure while a new matched pair of reflectors gets selected and the correcting filters redone.

Posted by Louis Bornwasser (Member # 3063) on 03-12-2010, 08:59 AM:

I, too, have never seen a S Lumex reflector without the heat coating.

If yours says "5400" it is very old. The code was meant to stop complaints from theatre personnel starting way back in the 80's.

btw: the very nearly worthless Chrsitie CH-20-25-10 can be made to be nearly as bright as the Super Lumex. Hadden (and others) have made a reflector kit available for at least 30 years. (The Christie is reliable, though!) Louis

Posted by Phil Hill (Member # 371) on 03-12-2010, 03:25 PM:

Strong Cinema Products uses a 3-letter code to identify the color temperature of their lamphouse reflectors. The code letters are located on the outside surface of each reflector. After decoding, a zero is added in the 4th place of the code to obtain the color temperature in degrees Kelvin. The codes are as follows:

A = 9

B = 5

C = 1

D = 4

E = 8

F = 2

G = 7

H = 0

I = 3

J = 6

Example: Code B J H = 5 6 0 + 0 = 5600°K.