All darkroom lights are unsafe under certain conditions but some are safer than others. Then again the safelight, by which we mean the colored glasses through which the light is filtered, may be made unsafe by merely changing the lamp behind it.

In our September number we published under the heading "Safelights," an article which went into this matter very thoroughly and gave the standard of safety which has been adopted for the Wratten Safelight lamps. However, we have recently learned of several cases where these lights have been declared unsafe, but we wish to show how, in each case, the light has been made unsafe by using a lamp of too great candle power.

Any light, if it is too intense, will affect a plate, but to secure the best light for various plates, a standard of safety had to be adopted. With the safelight recommended for a certain plate this standard permits a dry plate to be exposed for one-half minute at three feet from the light with no danger of fogging, provided a 16 c. p. carbon or a 25 watt Mazda lamp is used. In each case where these lights have been unsafe either a 40 watt lamp has been substituted for the 25 watt recommended or the lamp was used nearer than the prescribed three feet.

Unsafe Darkroom Lights StudioLightMagazine1915 254

FROM AN ARTURA IRIS PRINT

By Frank Scott Clark Detroit, Mich.

Unsafe Darkroom Lights StudioLightMagazine1915 256

FROM AN ARTURA IRIS PRINT

By Frank Scott Clark Detroit, Mich.

This same safelight lamp may be used at 18 inches with perfect safety if an 8 c. p. carbon or 10 watt Mazda lamp is used, or it may be used with a 40 watt Mazda lamp if the safelight is something like five feet from the developing tray. However, it is readily seen that the strength of the light that reaches the plate must be the same in each case if the light is to remain safe.

Some photographers may not think our standard gives a sufficient degree of safety, in which case a smaller candle power lamp may be used. It should be understood, however, that when we say a plate may be exposed for one-half minute at three feet from the light that we refer to a dry plate and not one that is in the developing solution.

The actual time your dry plate need be exposed to the darkroom light is never over a few seconds. And once it is in the developer the action of the light on the plate is less. And as your developing tray is seldom in the direct rays of light the only danger is from examining the plate too often or for too long a time during development.So we think our standard of safety for the Wratten Safelights is reasonable and one that is best suited to the average worker who wants as much safe light as possible.

You can develop plates with absolute safety with ordinary care or you can double the safety of your light and be as careless as you like, but you can't use lamps of greater candle power than are recommended and still have a safelight that is safe.