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Author Topic: When to use a heat shield (-edit heat filter) Kirk Futrell Film Handler Posts: 95 From: Nashville, TN / U.S.A. Registered: Nov 2008 posted 01-07-2010 10:50 AM                        We are installing a reel to reel set up with Simplex model 1050's and Strong super 80 lamphouses on pedestals. We will be using 3k bulbs. One of the used lamphouses has a heat shield attachment before the snood with a heat lens in it and the other doesn't. Should I take the heat shield out or buy one for the one that doesn't have one? In general when are heat shields necessary to protect the film?  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 01-07-2010 10:56 AM                     It's not a heat shield actually... You use those when you re-enter the atmosphere from space. Unless you have a lamphouse with a beam spreader lens in there it's generally called a heat filter or heat mirror. It has a special interference coating that reflects the UV and IR light spectrum. I absolutely reccomend it with 3kw lamps, especially if your projectors do not have water cooling on the gate. When you install new ones be sure they are at the correct angle and pointing at a heat sink surface in the lamphouse... not directly back at the lamp itself. Also be sure the coating side is towards the lamp!!! If it's the other way around the new heat filter will probably crack in a short time. Also, if your lamphouse happens to be obsolete you can get the heat filters custom made by Ultra Flat. I reccomend replacing both at the same time and yes, they are a bit expensive to buy. Again, knowing the make.model of your lamphouse or posting a picture would help us determine if it's a beam spreader or heat mirror... Mark  |  IP: Logged Kirk Futrell Film Handler Posts: 95 From: Nashville, TN / U.S.A. Registered: Nov 2008 posted 01-07-2010 11:32 AM                        Thanks for the info. The lamphouses are Strong Super 80's one made in 92 and the other in 2000. When looking through the manual it mentions you can use the lens holder as a beam expander, as you mentioned, or a heat filter for 35mm if you run 4500 watts and up. So, two more questions: How can I tell a beam expander from a heat filter, and what are the benefits to presentation and film preservation, of having a heat filter with a 3000 watt bulb?  |  IP: Logged Dave Macaulay Film God Posts: 2321 From: Toronto, Canada Registered: Apr 2001 posted 01-07-2010 12:13 PM                     The beam expander is a lens, ie the glass is not flat. The heat filter is flat glass. The beam spreader is for 70mm use. The mounting ring of the heat filter should have a sticker with an arrow and "towards lamp" or such. The filter glass is attached at a slight angle to reflect the IR and UV off to one side, not straight back to the lamp. Stron uses something that doesn't survive too long to hold the glass like this, and often the disk is just rattling around loose. You can use a bit of black RTV at the brackets to holt it off-axis, just have the glass out against one support and at the other extreme on the opposite support. If there's no sticker you can tell which side is coated: sight at a low angle above the glass to see a reflection from a bright light. You'll see two reflections, one from each side of the glass plate. The coated surface reflects with a purplish color, the uncoated surface reflects true color. When the purplish reflection is above the clear one you're looking at the coated side.  |  IP: Logged John Walsh Film God Posts: 2490 From: Connecticut, USA, Earth, Milky Way Registered: Oct 1999 posted 01-07-2010 04:59 PM                     For myself, I find that you can do OK without a heat filter up to and including 3K, providing other cooling 'parts' are OK (internal blowers are clean, roof exhaust fan at proper level, etc.) While the heat is reduced by about 50%, it also reduces the light by about 15% so there is a trade-off. I feel there is no sense putting in a heat filter for a 3K lamp if the light on screen is already significantly less than 16fL. Also, they don't last forever; I find after about 5 years, the coating has lost much of it's effectivness. They are nice, though when you need to clean the projector and the trap is not too hot to hold!  |  IP: Logged

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