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The spectra direct readine color temperature meter
CURRENT TOPICS The Spectra Direct Reading Color Temperature Meter.--The S P E C T R A Direct Reading Color Temperature M e t e r made by P h o t o Research Corporation, San Fernando, California, is the first instrument offered to the general public for measuring the exact color of a source of illumination. It operates photo-electrically and is therefore independent of individual eyesight and personal judgment. Everyone is familiar with the fact t h a t the appearance of objects depends greatly upon the illumination which falls on them. Even an unobservant person c a n n o t fail to note the difference between objects seen u n d e r sunlight and candlelight, and every woman knows t h a t colors which match under tungsten light do not match in daylight. These, however, are large differences of which almost everyone is aware. In recent years, the growing importance of color photography, and the increasing need of precise color matching in many fields, has made it necessary to deal with much smaller differences--differences which the human eye is totally unable t o perceive because of its ability to a d a p t itself to them, y e t which can seriously impair the correctness of color matching or of a color photograph. Practically no light source in common use furnishes light of constant, known color. Sunlight varies in color with the time of day, the season, the weather, the altitude, and many o t h e r factors. Tungsten light is somewhat more constant, b u t serious variations occur which depend on the wattage of the lamp, its age, the voltage a t the lamp (which varies widelv in most communities) and o t h e r influences. For a decade or more there has been a need for an instrument which would measure the color of a source of illumination in a precise way, so t h a t suitable corrective measures might be applied. That need has finally been met in the SPECTRA. The S P E C T R A is simple in principle, and no special knowledge or skill is required for its operation. In o r d e r to measure the color of illumination, we must have some sort of units in which to measure it. Fortunately, such a scale of measurement already exists in the laboratory. It is known as Color Temperature. It is not necessary to understand Color Temperature in order to use the SPECTRA, but for those who are interested in understanding how it operates, here is a brief explanation : The Color Temperature of a light source is the Kelvin temperature to which a black body would have to be h e a t e d in o r d e r to give off light of the same color. The Kelvin temperature is measured in degrees Centigrade above Absolute Zero. When we know the Color Temperature of a light source, we can say exactly how much red, yellow, green, blue and violet is contained in the illumination. Similarly, if we know how much of these colors is in the light, we can compute the Color Temperature. 89
I9o
CURRENT TOPICS
[J. F. I.
Fortunately, it is not necessary to follow such a complicated procedure. It is sufficient to measure the amount of any two colors in the light source, and t h e ratio between those two colors will correspond to one Color Temperature, and one only. This is what is done in the SPECTRA. First, t h e S P E C T R A is pointed a t the light source which we wish to measure. It is now measuring the red content of the light. W e adjust a ring so as to bring the needle on the scale to a red mark. This adjusts our red reading to a standard value. T h e n we pull t h e trigger on the SPECTRA. This moves the red filter o u t of the way and swings a blue filter in front of t h e light sensitive cell. With the trigger held back, t h e needle now tells us on the scale t h e exact Color Temperature of the light source. That is all there is t o it. If we are taking a color photograph on Daylight Type film, t h e light should be 5900 K. F o r T y p e A or Photoflood film, it should be 3400 K., and for T y p e B or Tungsten, 3200 K. If the S P E C T R A shows a departure from the correct figure, corrective measures must b e taken, such as the use of filters, as explained in t h e directions furnished with t h e meter. An important feature of t h e S P E C T R A is t h e Spectrasphere, a diffusing hemisphere which is placed over the instrument when light of mixed character is t o be measured. Out of doors, for example, directsunlight and light coming from the sky are not of the same color. Indoors, several lamps may be in use which are not of exactly the same color. The Spectrasphere mixes and averages u p t h e various light sources, and provides a figure which is the best guide to t h e most favorable results.
Farm Alcohol M a k e s Low-Octane Motor Fuel Equal to Regular Gasoline.On two recent trips of nearly 1000 miles each, a U. S. Department of Agriculture test truck ran successfully on relatively inexpensive low-octane gasoline fortified b y periodic injections of alcohol and water. Results of these longdistance road trials, according to t h e Department's Bureau of Agricultural and Industrial Chemistry, show how using alcohol in motor vehicles can help conserve petroleum a n d provide a potentially vast new market for surplus grains. The tests were made as part of the motor-fuels work financed under the Research a n d Marketing Act. Bureau researchers report t h a t in the first trial the truck operated as well on 58-octane gasoline plus alcohol-water injection as it would on regular gasoline, which has a n o c t a n e rating of 74 or better. The alcohol-water mixture (85 per cent alcohol, 15 per cent water) was injected automatically into the truck's carburetor when t h e engine was under h e a v y load, as in climbing hills, accelerating in traffic, or passing other vehicles. This enabled the engine to give knock-free performance even with the low-octane gasoline. For the second trial run the engine of the truck was equipped with a high compression head (8.25-to-1 compression ratio). This made it necessary to supply t h e engine with fuel having a n effective octane rating of a t least 85. On this trip 74-octane gasoline plus alcohol-water injection was used satisfactorily. Because of t h e tremendous consumption of motor fuels--more than 80 million gallons a day--general adoption of alcohol-water injection could open up a wide new outlet for surplus grains a n d o t h e r agricultural commodities. Alcohol can be made from a variety of these products. The usual method is
I9o
CURRENT TOPICS
[J. F. I.
Fortunately, it is not necessary to follow such a complicated procedure. It is sufficient to measure the amount of any two colors in the light source, and t h e ratio between those two colors will correspond to one Color Temperature, and one only. This is what is done in the SPECTRA. First, t h e S P E C T R A is pointed a t the light source which we wish to measure. It is now measuring the red content of the light. W e adjust a ring so as to bring the needle on the scale to a red mark. This adjusts our red reading to a standard value. T h e n we pull t h e trigger on the SPECTRA. This moves the red filter o u t of the way and swings a blue filter in front of t h e light sensitive cell. With the trigger held back, t h e needle now tells us on the scale t h e exact Color Temperature of the light source. That is all there is t o it. If we are taking a color photograph on Daylight Type film, t h e light should be 5900 K. F o r T y p e A or Photoflood film, it should be 3400 K., and for T y p e B or Tungsten, 3200 K. If the S P E C T R A shows a departure from the correct figure, corrective measures must b e taken, such as the use of filters, as explained in t h e directions furnished with t h e meter. An important feature of t h e S P E C T R A is t h e Spectrasphere, a diffusing hemisphere which is placed over the instrument when light of mixed character is t o be measured. Out of doors, for example, directsunlight and light coming from the sky are not of the same color. Indoors, several lamps may be in use which are not of exactly the same color. The Spectrasphere mixes and averages u p t h e various light sources, and provides a figure which is the best guide to t h e most favorable results.
Farm Alcohol M a k e s Low-Octane Motor Fuel Equal to Regular Gasoline.On two recent trips of nearly 1000 miles each, a U. S. Department of Agriculture test truck ran successfully on relatively inexpensive low-octane gasoline fortified b y periodic injections of alcohol and water. Results of these longdistance road trials, according to t h e Department's Bureau of Agricultural and Industrial Chemistry, show how using alcohol in motor vehicles can help conserve petroleum a n d provide a potentially vast new market for surplus grains. The tests were made as part of the motor-fuels work financed under the Research a n d Marketing Act. Bureau researchers report t h a t in the first trial the truck operated as well on 58-octane gasoline plus alcohol-water injection as it would on regular gasoline, which has a n o c t a n e rating of 74 or better. The alcohol-water mixture (85 per cent alcohol, 15 per cent water) was injected automatically into the truck's carburetor when t h e engine was under h e a v y load, as in climbing hills, accelerating in traffic, or passing other vehicles. This enabled the engine to give knock-free performance even with the low-octane gasoline. For the second trial run the engine of the truck was equipped with a high compression head (8.25-to-1 compression ratio). This made it necessary to supply t h e engine with fuel having a n effective octane rating of a t least 85. On this trip 74-octane gasoline plus alcohol-water injection was used satisfactorily. Because of t h e tremendous consumption of motor fuels--more than 80 million gallons a day--general adoption of alcohol-water injection could open up a wide new outlet for surplus grains a n d o t h e r agricultural commodities. Alcohol can be made from a variety of these products. The usual method is