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#1 Eliott Ward

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Posted 11 March 2006 - 03:50 PM

I wanted to create a Venetian blind pattern.

I first tried a real set of venetians and later a 4x4 frame with 2" tape on it. (neither one seemed any better then the other)

I used an open face lamp, 1500W. I flooded it and moved it back, expecting to see a nice pattern...but it was very indistinct.

Strangely when I closed the barn doors some (reducing intensity unfortunately) or even held up my hand in front of the light (again, taking down intensity) the pattern got much more distinct.

Why is this? I would have thought an open face lamp would be perfect for this. Moving the light back further didn't help.

Obviously, there's some characteristic to this light that is not conducive to casting a distinct pattern. But i thought such a strong point source is exactly what we would have wanted.

Thanks for any help.

Eliott Barnes
Los Angeles
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#2 Luke Prendergast

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Posted 11 March 2006 - 04:22 PM

But i thought such a strong point source is exactly what we would have wanted.


Ah, but an open-faced fixture is not a point source - it has a reflector behind it.
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#3 David Mullen ASC

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Posted 11 March 2006 - 05:25 PM

A fresnel with the lens removed is even better, but then it's not as bright. Try a 2K or 5K fresnel with the lens removed.

A really bright light backed FAR away would be sharp.

I've lit things with the sharp edge spill from an HMI PAR with a lens in front, the light at a right angle to the subject -- but it's not very efficient.
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#4 Michael Nash

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Posted 11 March 2006 - 09:40 PM

Strangely when I closed the barn doors some (reducing intensity unfortunately) or even held up my hand in front of the light (again, taking down intensity) the pattern got much more distinct.

Why is this?


You need a very small, point source of light to create a sharp shadow. Closing the barn doors a bit or side-cutting the light makes the light source a smaller point, and the shadow therefore sharper.

But obviously you also need a more powerful light if the shadow is to be sharp AND the light bright enough. Sometimes you can use some form of ellipsoidal light to create a more focused shadow, but at the expense of spread. Dedo's, source-4's, or spotlights like a Supertrooper can work.
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#5 Hal Smith

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Posted 11 March 2006 - 10:09 PM

I wanted to create a Venetian blind pattern.

I first tried a real set of venetians and later a 4x4 frame with 2" tape on it. (neither one seemed any better then the other)

I used an open face lamp, 1500W. I flooded it and moved it back, expecting to see a nice pattern...but it was very indistinct.

Strangely when I closed the barn doors some (reducing intensity unfortunately) or even held up my hand in front of the light (again, taking down intensity) the pattern got much more distinct.

Why is this? I would have thought an open face lamp would be perfect for this. Moving the light back further didn't help.

Obviously, there's some characteristic to this light that is not conducive to casting a distinct pattern. But i thought such a strong point source is exactly what we would have wanted.

Thanks for any help.



Eliott Barnes
Los Angeles

How many footcandles do you need in the lit portion of the venetian blind pattern? How large a pattern (H X W)? You might be within the performance parameters of an ETC Source Four Ellipsoidal with a Gobo in it. If you can give me the requested information and an idea of what kind of shot you're planning, I might be able to help.

I lit the final scene in a stage production of "Driving Miss Daisy" with an S4 and a blinds gobo projecting across the stage to the table where Hoke is feeding Daisy (and a very low key general wash with a bit of eye light for Daisy and Hoke). When the nurse wheeled Daisy in through the pattern the effect was breathtaking - the director of the production was an Emmy winning TV producer, he flipped when he saw the "look" for the first time in tech rehearsal. We don't use gobos projected by lekos all that much in movie making but they do have their strong points. ETC just came out with optional lens tubes for Source Four's that have improved optics specifically for gobo and image slide projection.

Look at http://www.rosco.com...log/window.html to get an idea of what's available. The other gel and pattern companies also have libraries of window gobos.

Edmond, OK
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#6 Adam Frisch FSF

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Posted 13 March 2006 - 07:09 AM

Warning! Don't ever operate a HMI with the lens removed. The UV protection is in the lens and will not only give skin burn but might damage the eyes permanently.
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#7 Dino Giammattei

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Posted 16 June 2006 - 05:00 AM

Kinda like looking at an arc welder...
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#8 Michael Nash

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Posted 16 June 2006 - 03:20 PM

Kinda like looking at an arc welder...


Worse. You'll feel an arch welder, as anyone who's ever been "flashed" can tell you. You don't feel the UV damage from HMI's when it happens. That's what makes it so dangerous.
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#9 Bob Hayes

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Posted 16 June 2006 - 03:54 PM

Sometimes putting a c-stand arm horizontal through the beam will help. But my first choice is, as David said, as fresnel with the lens removed. You can just open the door with the lens on it.
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