Download Safelight
Niccoletta Vullo
A safelight is a light source suitable for use in a photographic darkroom. It provides illumination only from parts of the visible spectrum to which the photographic material in use is nearly, or completely insensitive.
A safelight usually consists of an ordinary light bulb in a housing closed off by a coloured filter, but sometimes a special light bulb or fluorescent tube with suitable filter material or phosphor (in fluorescent tubes) coated directly on the glass is used in an ordinary fixture.
Differently sensitised materials require different safelights. In traditional black-and-white photographic printing, photographic papers normally are handled under an amber or red safelight, as such papers typically are sensitive only to blue and green light. Orthochromatic papers and films are also sensitive to yellow light and must be used only with a deep red safelight, not with an amber one.[1] Panchromatic films and papers, nominally sensitive to the entire spectrum, sometimes have a region of minimum in their range of sensitivity that allows the careful use of safelight confined to that part of the spectrum. For example, Kodak Panalure panchromatic paper is tolerant of limited exposure to light filtered through a Kodak 13 Safelight Filter.[2] Other panchromatic materials must be handled only in total darkness.
Many photosensitive materials used in technical and industrial applications, such as photoresist, are sensitive only to blue, violet, and ultraviolet light and may be handled under a brighter yellow safelight. Low-pressure sodium vapour lamps sometimes are used in larger industrial darkrooms. They emit nearly monochromatic light at 589 nm (yellow), to which the materials are insensitive; as a result they can be extremely bright while still "safe".[citation needed]
Has anyone tried or heard of a green safelight that can be used in a dark room for black and white film loading? The first person who mentioned this to me about 10 years ago is a notorious chain yanker but someone mentioned it again recently.
Not that I'm trying to change many years of habit by introducing a safe light for loading my reels, just real curious if it's true and why I never heard of it before.
4:12PM, 4 February 2011 PST(permalink)
The short answer is yes, there is a safelight for film development (Kodak #3 dark green) but it's not really the equivalent of the safelight used for making prints. It's for development by inspection when the film has been mostly developed, and can only be used for very brief periods. More here.
ages ago(permalink)
A dark green safelight is allegedly OK for (some) panchromatic film, as long as it's indirect illumination (i.e. you stand between the film and the bulb).
Red is OK for ortho, green is not.
Panchro has a dip in sensitivity around green, which eyes also happen to be very sensitive to.
I would avoid using anything other than infrared light/goggles for darkroom use (obviously not OK for HIE or whatever though).
ages ago(permalink)
The entire reason for a green safelight has nothing to do with the sensitivity of the film. Panchromatic film is sensitive to all visible wavelengths of light. Rather, it has to do with the fact that the human eye is most sensitive to green light. This is also the reason why the fire exit signs in buildings are changing from red to green.
ages ago(permalink)
Kodak issue recommendations for some panchro films saying that you can develop by inspection by using a dark green safelight about thirty miles away from the film.
You can't use it for undeveloped film though, as it will fog unless it's so dim as to be useless to you.
ages ago(permalink)
Joao,Most B&W papers are orthochromatic, meaning that they are not sensitive to
red light. The exception I can think of is Kodak Panalure Select which is
panchromatic so that it can be used with color negs. I use Ilford MG IV
with a red safelight and find that it works just fine. Many makers of B&W
paper suggest using the Kodak OC safelight because its brownish/amber
color is safe and is easier to see by. Whenever I try a new paper I
always do a safelight test just to make sure. Hope this helps. :-)Eric Dawson
When he refers to "process" films, he's talking about ortho film. The kind
used by printshops for black & white line art. It can be developed under
a red safelight.Cheers, Rene
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A safelight is a type of lighting fixture used to provide working light in photographic darkrooms. By definition, the safelight is a light source emitting light in an area of the spectrum that does not affect the light sensitive materials for which it is designed.
A safelight is essential in any darkroom, as it provides illumination without affecting the photographic materials. Many darkroom processes would be impossible or impractical without a safelight. Safelights are also utilised in most other fascilities handling photosensitive materials like medical imagery labs (x-ray radiology), lithography printing outfits and others.
There are different types of safelights for different light sensitive materials. Depending on the type of material, there may or may not be a safelight available for it. Modern panchromatic photography film is sensitive to all parts of the visible light spectrum, so no safelight is suitable for it. Such materials may sometimes be handled under infrared light with suitable optical aids.
On the other hand, orthochromatic film is only sensitive to blue and green light and can be safely used under a red safelight. This is also the case with most black and white printing papers, although there are some specifics which we will cover below.
There are several different types of safelights on the market, and they differ mainly in their light filtering mechanism. There are two principal approaches to a safelight: a full spectrum lightsource behind a filtering medium or a narrow band light emitter. For most of the history of photographic printing, safelights have been predominantly of the former type. Only recently, with the rapid development of narrow band LED light sources, did the latter kind emerge. Today, both are readily available, either new or on the second hand market. Here are the most popular safelight types with their advantages and disadvantages:
Probably the most traditional type of darkroom safelight fixture consists of a housing with a bulb socket and a filter frame. One such model is the Kaiser Darkroom Safelight pictured above. The main advantage of this design is the flexibility it provides. The interchangeable filters to allow the safelight to work with a variety of light sensitive materials.
Another traditional photographic safelight is the bare bulb safelight like the Delta 1 pictured above. It is the simplest kind of safelight, as it is just a regular light bulb coated with filtering material.
A properly selected LED is therefore a perfect safelight source, as all the light that is emitted is within the safe spectrum. Such LEDs require no filtering and there is no filter factor light loss. Compared to an incandescent bulb behind a filter, where a large percentage of the light is absorbed by the filter, LEDs are extremely efficient. Subsequently, LEDs also produce very little heat in operation, which can be very benefitial in a small, non air conditioned darkroom.
A key advantage of the narrow spectral output of LEDs is that you can make your darkroom as bright as you want. Generally LEDs allow much higher darkroom illumination for far longer than traditional incandescent safelights. Of course, as with any other safelight lamp, you need to test your particular setup before you begin printing.
While the classic red safelight is the vastly recognizable darkroom staple, it is far from the only type of safelight used. Digging deeper, you will stumble upon safelights described as amber, brown, yellow-green and others. In reality, the colour of the safelight is just an easier (and less accurate) way to describe the spectrum range of light it outputs.
ILFORD MULTIGRADE papers can be used with most common safelights for black and white papers. The ILFORD safelights are especially recommended as they generally allow darkrooms to be brighter, but completely safe. For direct lighting, do not expose the paper to the safelight for more than 4 minutes, and the distance between the paper and the safelight should be a minimum of 1.2 metres/4ft.
From the chart above, we can see that the paper is sensitive to the light spectrum from about 370nm to 550nm. What this means is that any safelight filter that filters out these wavelenghts is suitable for use with Ilford Multigrade. A classic Kodak 1 safelight filter will do nicely with this paper. Looking at this from an LED safelight point of view, any fixture emitting light from about 600nm upwards (to be on the safe side) is fine. Bear in mind that the higher you go, the less visible the light will be. In this example you might want to stick between 600nm and 650nm. Anything above 650-700nm starts getting outside of the visible spectrum and into infrared.
If you are equipping a dedicated darkroom and intend on doing various processes there you might need something more durable and flexible. A classic interchangeable filter fixture with the corresponding filters for your processes is a comprehensive solution. Alternatively, another option can be a dedicated LED safelight. Some advanced models like the Heiland above offer selectable spectral outputs within one unit, including a white light mode for regular viewing.
The one area where safelight illumination control matters most is the enlarger baseboard or easel. If the safelight intensity in this area is too strong, you will have a hard time seeing and focusing the image projected by the enlarger. It might also interfere with the use of a focus finder or when doing any dodging and burning. Furthermore, you will increase the risks of paper fogging with prolonged exposure.
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