Modern, high performance bulbs guarantee short exposure times, high dot-to-dot accuracy and thus perfect exposure results. To achieve this performance however, one has to make sure to use a bulb which emits high energy levels in the spectral region where the material being exposed is most sensitive. Metal-Halide bulbs are the light source of choice for most exposure applications. They have come a long way since they first replaced pulsed xenon and carbon arc systems. Because of the wide variety of MH-bulbs available, the wrong type is often used for a specific application. Unlike regular light bulbs which emit light in a rather continuous and smooth curve along the light spectrum, high intensity metal halide bulbs emit relatively narrow but very intense peaks of energy at specific wave-lengths. By mixing additives into the bulbs, manufacturers are able to adjust the wave-lengths of these peaks, tuning them to match the response curve of a particular type of material. Since each imaging product is only sensitive to a limited region of the light spectrum, it is very important to have the right bulb for the material being used. The optimum bulb emits its energy at a wavelength that closely matches the spectral sensitivity of the material being exposed. The manufacturer of your film or plate, or your local sales rep can obtain the spectral sensitivity curves of the material you are using. Finding a bulb which matches the spectral sensitivity of your material is essential. Lamp Express came up with a new way of showing the spectral output of bulbs - Donuts ! The number in the center of the donut corresponds with the ending number of all Theimer bulbs. The popular THS 8027 for example, ends with the number 7. This means that this bulb generates the spectral output as shown in the donut with the number 7 in its center. The THO 5040, a high quality replacement bulb for the Olec L1280, generates the output as shown by the 0 - series donut. Each donuts graphically indicates how many % of a bulbs output is in a specific wavelength range. Now just look into the data sheet of your plate- or film material to find out where it is most sensitive and compare it with the LE donuts. O - Series Bulbs 7 - Series Bulbs 8 - Series Bulbs 9 - Series Bulbs