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This topic comprises 3 pages: 1 2 3
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Author
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Topic: Rotating Xenons? Pro or Con?
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Pat Moore
Master Film Handler
Posts: 363
Registered: Mar 2000
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posted 04-14-2002 09:41 AM
I'll side with Steve and stick with my previous thoughts. Again, I've not seen the Magnacom's be "light eaters", especially if they are properly coupled with lens focal lengths they are designed to work with. The new Zoom Converters are much better than the old Magnacoms. It's more like newer technologies are more light efficient. Generally (emphasize "generally"), I would prefer a fixed prime lens instead of a prime coupled to a Zoom or especially to a Magnacom, but there are a lot of instances where Zooms are an excellent tool and can actually be a better choice. Curved screens are a great example.Yes, if I take a Zoom Converter, properly coupled to the correct prime lens and compare it to a fixed focal length lens of the same resulting focal length, the light levels will be very close. Not too many years ago the combination would have been brighter and more uniform on screen than the single prime, but improvements over the past decade and especially in the last couple of years with prime lenses has changed that. I think there is still a place for Zooms, though, in some applications and have had great results with them. Does that mean I'd put them in every theatre? Nope. Brad, sounds like there are application and/or coupling problems in your example. The true Magnacom didn't like working with a prime lens below 70mm (I think), and it needed close couplers to do that. Otherwise you will see vignetting and probably light loss as well. The Magnacom is nominally a 65% magnifier, so coupled to a 70mm lens the resulting focal length is around 45mm. To get to 40mm or below, they are coupled to 60 or 65mm and that's probably where the problem lies. If it's a late 80's installation, who knows what might be in there. Like most things, a Magnacom is just a tool that functions fairly well if it's properly used. Newer tools and technologies do tend to be better, if properly used. Pat
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John Pytlak
Film God
Posts: 9987
From: Rochester, NY 14650-1922
Registered: Jan 2000
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posted 04-15-2002 10:03 AM
Pat Moore asked: "John -- by "shim", I assume you refer to a washer that would be used on "HTP" style lamps, right? I think washers are normally provided by the lamp manufacturers for 180-degree rotation."Yes, I meant the lamps that have the screw-in base. Didn't know if they came with shims/washers to allow 90-degree rotation increments. ------------------
John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Research Labs, Building 69, Room 7525A
Rochester, New York, 14650-1922 USA
Tel: +1 585 477 5325 Cell: +1 585 781 4036 Fax: +1 585 722 7243
E-Mail: john.pytlak@kodak.com
Web site: http://www.kodak.com/go/motion
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