Barrel
The Source Four is the first fixture to feature a rotating shutter barrel, which makes framing objects much easier regardless of lamp orientation. In previous fixtures, the shutters had only a limited range of motion and could not be rotated. The shutters are also made from stainless steel, which does not warp easily under the heat of the lamp. The shutters are arranged in 3 planes, allowing a degree of freedom in shutter placement by the extreme angles they can be racked to. The top and bottom shutters are on their own plane, with the 2 side shutters sharing a single plane. Occasionally with difficult shots and extreme shutter angles this sometimes causes the side shutters to hit each other, preventing a perfect focus. One option is to rotate the shutter assembly and try to achieve the same effect with different shutters. A more extreme work around is to remove the shutter assembly from the unit body and reattach it 90° offset, so that the bottom and top shutters effectively become the side shutters.
ETC also offers a variety of interchangeable lens tubes with various field angles. These are: 90, 70, 50, 36, 26, 19, 14, 10, and 5 degree lens tubes, some of which are available as enhanced definition lens tubes (EDLT). The Source Four is also available as a zoom fixture, with a non-interchangeable lens tube. According to ETC's manual, the lenses in each lens tube cannot be reoriented, added or removed. Lenses come from the factory with a painted-on dot denoting the front face. The inside of the lens tube shows which slot is for which lens.
Different field angles are needed for different venues with different catwalk and electric systems (and, therefore, different throws). A lens tube with a smaller field angle will light an area from far away, whereas a large beam degree such as a 90 degree can be much closer in order to light the same area. A 90 degree Source Four might be used to project a gobo from the rear only 5 feet away on a scrim at the back of the stage, while a 10 degree could be used in the back of the house, for example, in the technical booth where a technician could access it to refocus or change gobos during a show. A zoom gives the option of adjusting the field angle within a specified range without changing the lens tube. This is needed in the case of lighting fixtures that need to be re-focused frequently to different areas of the performing area, without having to rehang them in a different position in the lighting rig. There are two Source Four Zoom fixtures, the 15-30 degree and the 25-50 degree.
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Famous quotes containing the word barrel:
“My long two-pointed ladder’s sticking through a tree
Toward heaven still,
And there’s a barrel that I didn’t fill
Beside it, and there may be two or three
Apples I didn’t pick upon some bough.
But I am done with apple-picking now.”
—Robert Frost (1874–1963)
“Peaches grow wild, and pigs can live in clover;
A barrel of salted herrings lasts a year;
The spring begins before the winter’s over.”
—Elinor Wylie (1885–1928)
“I do not know if you remember the tale of the girl who saves the ship under mutiny by sitting on the powder barrel with her lighted torch ... and all the time knowing that it is empty? This has seemed to me a charming image of the women of my time. There they were, keeping the world in order ... by sitting on the mystery of life, and knowing themselves that there was no mystery.”
—Isak Dinesen [Karen Blixen] (1885–1962)