Too many variables to answer:

How efficient is the illumination system of the projector?

What is the gain of the screen?

Most tungsten lamp 16mm projectors should be able to handle a screen up to about 2 metres wide with good illumination.

But it is best to actually measure the screen luminance:
http://www.kodak.com/US/en/motion/newsletters/pytlak/spring98.shtml
http://www.kodak.com/US/en/motion/newsletters/pytlak/march2000.shtml
http://www.kodak.com/US/en/motion/newsletters/pytlak/june2000.shtml

Their light output was to the naked eye virtually identical, though as you'd expect, the colour temperature was radically different. I did once have to run a show with these two machines that included a changeover, and a customer remarked that it was a pity that the colour seemed to have faded so much during the last half of the film!

For what it's worth, I suspect that the reason why 50mm primes are shipped as standard is that 16mm portables were intended to be used in classrooms, training and conference situations rather than in homes. In this kind of environment you would typically want a throw of 5 to 10 metres rather than the 2 to 3 you have in a living room.

Peter,

I hope you will able to get a very good quality 25mm lens to double your picture width. With my 25’ throw I upgraded my standard 50mm lens for academy & scope. And purchased a good quality 37.5mm size lens for 1.85 wide.

My first projector was a Bell & Howell 631, had a variable aperture plate, which worked satisfactory on a masked screen. The RCA was much better though with the 1.85 aperture plate machined and fixed into a set of gate runners, I was able to file out the plate to fit precisely. Also a vast improvement with the RCA compared to the B & H was the extremely smooth optical framing adjustment by the claw movement.

Here is a picture of the best type of Tape Film Splicer to look out for, made in Italy by CIR would be ideal for you. The special myler splicing tape you will need is 15mm in width. I didn’t bother doing a photo of my Rewinder as it is duel 16/35 which is geared ideal for 16mm 5000’ long play reels. You should be able to pick up a decent cheap small 16mm Rewinder just for 1600/2000 reels. Do check that the spool security clips are complete and sound though before you buy.

Very hard to get but very useful if you can get one is a variant of the 16mm CIR joiner in Bernard's picture which has a set of retractable pins on both edges of the film path, so you can tape over both sides without having to turn the film around horizontally.

Obviously, a xenon or metal-arc (Marc 300) lamp would be more efficient and a higher color temperature.

------------------
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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In terms of splicing at least oen distributor I have spoken to has indicated that they prefer that home users don't do any splicing. They would prefer that the film was returned and they will fix it. However for any films I buy a splicer would be handy.

Thanks John and others for the technical help. One day when everything is set up I'll see if I can find someone with a light meter to come around to my place and measure the light output of my projector and how changing the size of the screen affects teh luminosity.

cheers Peter

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For a given projector and lens, screen luminance is directly related to the image AREA. If you double the AREA, you halve the screen luminance. If you double the width (quadruple the AREA), you need four times more light from the projector.

Can someone please explain to me a little about lenses. I have a 50mm lens - doe the 50mm refer to the width of the lens or the focal length? Also why will a 25mm lens give me twice the size picture?

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