The matter of skylight construction for a photographic studio has always been debatable and any one seeking information on this subject experiences difficulty in obtaining advice which might be considered as authoritative.
The principles governing skylight construction are, however, extremely simple and it was on account of numerous requests for information on this subject that we published some years ago in Studio Light an explanation relating to the construction of a single slant skylight. Many photographers are, however, so situated that a single slant light does not meet their requirements. It therefore occurs to us that a supplementary article explaining the principles involved in the construction of skylights of various types will be of interest.
The accompanying diagram represents a cross section of a photographic studio 20 feet wide and 12 feet high. In this diagram the skylight comes within 3 feet of the floor and the vertical line A-B represents the simplest form of skylight construction. This is the form of "skylight" usually available when making home portraits in private houses. The dotted lines represent the general direction from which light is assumed to fall when entering any room through either a window or skylight. A glance at the diagram will show that if a vertical light were to be built for a room 20 feet wide, it would necessitate extreme height in order to secure illumination for the entire width of the room. Light falling in a straight line at an angle of 45 degrees from the top of the window should strike the opposite wall at about 5 feet from the floor to fully illuminate the room. In home portrait work where the height of an ordinary window does not exceed 8 or 9 feet it would be necessary to work very close to the window and the taking of large groups would not be practicable even in a large sized room. A vertical light for a room 20 feet wide should be 25 feet high.
In an ordinary studio, the construction of a light of this description would be out of the question, but for the photographer who can erect a studio building where a room of spacious proportions and stately height could be built, a vertical light constructed of plate glass with leaded sash would be the last word in efficiency and impressive-ness. Photographers who have the opportunity to build a light of this description are, however, so very few that we merely mention this in passing as the most simple form of light.
In considering the next form, commonly known as the "single slant light" which is represented by the line A-C, we have a sash placed at an angle of 70 degrees. The extreme height, from the floor, at the peak for a room 20 feet wide is 19 feet. If a skylight is to be constructed for a room of less width the proper height can easily be determined. This diagram is drawn to a scale of 3/16 inch to a foot. Lay a rule on the diagram and measure the distance from the floor to a point where the dotted lines, for a room of any specified width, intersect the heavy black line. By taking the distances in inches and dividing by 3/16 the result will be the height in feet. Experience has shown that for a single slant light the best angle at which sash should be placed is 70 degrees. This for the reason that a steeper angle would necessitate an unreasonable height and if light were placed at a lower angle there would be very considerable danger of breaking glass when moving back-grounds, head screens, etc.
The form of skylight which is perhaps in most general use is that indicated by lines A-D-E. This is what is commonly known as "top and side" and represents a vertical side light extending to an average height of 9 feet from the floor and a top light extending from this point at an angle of 45 degrees back far enough to intersect the dotted line representing the angle of light for a room of any given width.
The next form of skylight, commonly known as the "hip light," is represented by the lines A-F-G and is an excellent form of skylight construction, bringing, as it does, the average surface of the glass nearer to the subject. The lower sash being placed at an angle of 80 degrees and extending to a height of 9 feet from the floor permits of working very close to the light with back-grounds and other accessories. The upper sash running back at an angle of 45 degrees to the line of light intersection will give illumination to the extreme width of the room. As the curtains covering the skylight are operated at the plane of the glass this form of light permits of great concentration and accurate control. For either the form known as the "top and side" or the "hip" light the proper angle for the upper sash is 45 degrees for the reason that in this position light strikes the glass more nearly at right angles and passes through and into the room with least deflection.
The accompanying diagram and the above explanation relate to the proper heights and angles for skylights of various types - height and angle being the only factors which afford illumination to the entire width of the room. The width for a light has nothing to do with illumination beyond the angle of light intersection. The width is merely a matter of working convenience and depends largely upon the length of the room. Where there is sufficient length to permit of operating in either direction the most advantageous position for the light is in the center of the room and the light may advantageously occupy one-third of the whole side. With a studio of less spacious dimensions it would be advisable to leave a space of at least 4 to 6 feet at one end. The skylight may then occupy practically one-third of the remaining space, but if the room is very short it will undoubtedly be necessary to increase this proportion.They are a real economy, because they afford the means of cutting accurate masks easily and without bothersome measuring
The Great Event
Many photographers regard a visit to the Eastman School of Professional Photography as the most profitable trip they could take, but there are still a few who fail to take advantage of this opportunity for brushing up their working methods by attending the lectures and demonstrations, and to pick up new ideas from rubbing shoulders with other men in the same line of work.
All are invited.
All come, please!
Dates for the School in Toronto are Feb. 22, 23 and 24, at St. George's Hall; for Montreal, Feb. 29, March 1 and 2, at Coronation Hall.
FROM 1915 KODAK ADVERTISING CONTEST "Write it on the film - at the time"
By Percy DeGaston Tropico, Calif.
FROM 1915 KODAK ADVERTISING CONTEST "Let the children Kodak"
By Julius Schabtach Buffalo, N. Y.