## Section

The vortical angle of 30 at the spectator s position establishes the distance from the closest seat to the screen or to the highest significant object on the stage- The lowest seat in the orchestra must be located where the patron can just see the stage floor (except in the case of theaters built for motion pictures only). The highest seat in the balcony must be on a line which is not more than 30 to the horizontal at the front curtain at the stage floor if it is not to be above the limit of reasonable distortion. The standing patron at the back of the orchestra must be able to see the top of the screen, which is usually as high as any significant portion of a stage setting. Each spectator must see the whole stage or screen over the heads ol those in front of him Within these limits the floor slope of orchestra and balcony can be laid out; the first step in determining auditorium section. (See Fig, 19.)

Several methods have been offered heretofore for developing the floor slope. Doubtless others will be offered in the future. The authors present the following method as one which assures unobstructed vision from all seats. It may be noted that this system produces a floor slope considerably steeper thon that in many existing theaters. It also produces better seeing conditions.

To determine floor slope, establish eye position of spectator in first row on center line by approximately 30 vertical angle above. For live shows, stage floor will be approximately 2

in, below this level. For theaters designed solely for motion pictures, the location of the stage floor is not critical; the position ol the bottom of the screen is. (See Fig. 20.)

A point 3 ft 8 in. below, end 18 in. In front ol tha aye position will be ihe floor level for the front row. (I) Draw a sight line from the eye position to downstage edge of stage, and extend it back of the eye position for the front row, step off horizontal seat «pacing {back to back), end draw vertical lines at the points thus established <2) Establish a point 5 in. above the intersection of the extended sight line and the next vertical tine. (3) This is the eye position for the second row and the floor level at the front edge of the second row seat is 3 ft 8 in. below and 18 in. in front of the eye position. Repeat stepa (1), (2), and (3) lo the beck of the houaa and draw In the floor slope. Where the slope exceeds t % in, per foot, platforms are required under the seat a, and steps in the aisles. A cross eisle which dividea the orchestra into front and back sections enteils the elevation of the first row of seats behind it to make up for horizontel width of the aisle.

The standing spectator's eye level behind ihe rear row of seats is assumed to be 5 ft 6 in. above the floor level of the last row. The sight line Irom this position to the top of the screen or highest probable curtain trim establishes the minimum height for ceiling under balcony. (See Fig. 21.)

Raising the stage will make it possible to reduce the floor slope but et the penalty of producing upward sight lines in the first two or three rows which are uncomfortable end unnatural for viewing stage setting and action. If the stage floor is above the elevation of the first row eye position, the upstage floor out of sight by perhaps as much as 6 in. Irom the first row is generally preferable to having an excessive floor slope, especially if more than one balcony is used.

When planning for motion pictures only, the lower sight line from the first row will come to the bottom of the projected picture, approximately 24 in. above the stage floor, or still higher if a reverse floor slope ie planned.

In laying out the balcony, sight tines ere laid out from rear to front because it is unsafe to change balcony slope, Tha focal point onstage is tha point farthest downstage at which visibility is requisite, or, in the case of motion pictures only, the bottom of the screen. The maximum forward extenaity of the belcony Ie then determined when the location of the spectetor's eye position has been moved forward to a point beyond which the floor and supporting structure would intersect the upper sight tine of the spectator standing at the rear of the orcheatre.

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Fig, 20 (a) Maximum tolerable for motion picture», (hi Maximum lion of closest seats, (c) Basic

Fig. 19 Maximum tolerable downward sight line angle from balcony.

then 2 ft above the stage floor. Raising the screen makes it possible to flatten the contour of the orchestra floor. The reversed floor slope developed by Ben Schlanger makes use of thia relationship to get the maximum number of seats into the lone of least visual distortion, and to hold the height of motion picture theaters to a minimum. A result of tha reversed floor slope is to place balcony seats In the ion« of optimum seeing.

sight line angla determines locator plotting

The pitch of balcony floors should not change since that would entell e change of riser height for aisle steirs and introduce attendant hazards- If vision from the rest row in the balcony la adequate, the rest of the balcony is satisfactory.

In theaters designed only to show motion pictures, the first row need not be located so that tha patron can see the atoga floor. It is satisfactory if he sees without obstruction the bottom of the screen which is seldom placed less

Fig. 21 The sight line of the standing patron limits ihe balcony overhang.

It is apparent that a theater designed for maximum efficiency for motion pictures (reverse floor slope) is almost completely useless for sny other sort of production except large-screen television. The principle survives in the angle of the car stands in the drive-in motion picture theaters.

### Floor Dish

The planning of the floor slope is not completed when pitch of orchestra and balcony has been laid out on the center line. It depends also on the curve of the rows of seats. The whole row must be at the same elevation if the seats are to be level. The floor therefore ia not a sloped plane, but a dished surface in whioh horizontal contours follow tha seat row curve. The floor section at the center line, rotated horizontally about the oenter of curvature of the rows of seats, will determine the orchestra floor shape. The balcony is planned the same way save that the floor is terraced to take the seats. (See Fig. 22.}

### Comment

It has been established that conditions of seeing limit the depth of the house. Since capacity ia a function of depth and width, increasing the width increases the capacity. However, since sight lines from the side seats limit the angular spread of the aide walls, the width can be increased only by increasing the proscenium opening. The width of the proscenium opening is e function of the kind of production contemplated for the theater. The dimensions given in Table 1 are derived from the requirements of tha typea of produc-

TABLE 1 Proscenium Widths, in Feet, for Kinds of Theatrical Production

Fig. 19 Maximum tolerable downward sight line angle from balcony.

TABLE 1 Proscenium Widths, in Feet, for Kinds of Theatrical Production