8mm Forum: Two Blade Visuals

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Topic: Two Blade Visuals

Mark Todd
Film God

Posts: 3846
From: UK
Registered: Aug 2003

posted October 27, 2008 07:18 PM

Hi I was wondering what people who had an elmo converted to a two blade shutter thought regarding picture/light improvement.
GS1200 800 or 600 varients.
Interested in any thoughts.
Thanks Mark.

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Douglas Meltzer
Moderator

Posts: 4554
From: New York, NY, USA
Registered: Jun 2003

posted October 27, 2008 07:38 PM

Mark,

Ugo posted a while back that switching to a 2-bladed shutter increased light output by almost 100 lux. I haven't done the conversion since I occasionaly project at 18fps and using that shutter would cause a flicker problem. I know Paul Adsett raves (constantly!) about the surge in light output.

Doug

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I think there's room for just one more film.....

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Paul Adsett
Film God

Posts: 5003
From: USA
Registered: Jun 2003

posted October 28, 2008 10:17 AM

That's right Doug! I did a 2-blade conversion on one of my GS1200'S a few years ago, and the improvement in light output is very noticeable indeed. I know in theory it should boost light output by about 33%, but in practice it seems a lot more than that- the picture is just so much whiter. In comparison my regular 3-blade GS seems dull!
The only down side is flicker, which can be noticeable on small screens, even at 24fps. But above about a 60ins screen you should not notice it, except perhaps on very white scenes. The flicker is so bad at 18fps, that a 2-blde conversion essentially makes your machine 24 fps only.

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The best of all worlds- 8mm, super 8mm, 9.5mm, and HD Digital Projection,
Elmo GS1200 f1.0 2-blade
Eumig S938 Stereo f1.0 Ektar
Panasonic PT-AE4000U digital pj

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Mark Todd
Film God

Posts: 3846
From: UK
Registered: Aug 2003

posted October 29, 2008 06:59 AM

Hi Doug and Paul, thanks for that. I didn`t know about a bit of flicker at 24fps as well. Funny my Elmo 16AA has a two blade and even at a foot sized picture when just running a few to look over I can`t see any flicker at all.
I`m planning a 2 blade into a ST180 elmo and hoping its a good un for that job and will move things up image wise. Sounds possitve.
Best Mark.

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Paul Adsett
Film God

Posts: 5003
From: USA
Registered: Jun 2003

posted October 29, 2008 08:58 AM

Mark, do not be overly concerned about flicker at 24fps with a 2-blade shutter. The scientific fact is that flicker and brightness are related to each other and if you get the screen super bright you can even see flicker at 24 fps with 3 blades.
For all practical purposes you will not detect flicker when projecting normal density films with a 2-blade shutter at 24 fps on a decent sized screen.

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The best of all worlds- 8mm, super 8mm, 9.5mm, and HD Digital Projection,
Elmo GS1200 f1.0 2-blade
Eumig S938 Stereo f1.0 Ektar
Panasonic PT-AE4000U digital pj

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Mark Todd
Film God

Posts: 3846
From: UK
Registered: Aug 2003

posted October 29, 2008 10:01 AM

Hi Paul. Thanks. I`m working on the theory that with a 100 watt xenophot you have around 120 watts of light, plus 33% from the shutter upgrade takes you to around 160 watt`s only 20 watt`s behind a st1200 with the 150 watt xenophot in.
Sounds like a really good up grade and going to the place to get it done.
Best Mark.

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