Differences in Light Sources:
In your Exposure unit the light source is the key ingredient to good resolution, crisp images, and clean prints. It is what allows you to gain great detail or fast exposures.
There are 3 main types of lights commonly used in exposure units. There is multi point, single point, and a combination of the two. These are typically referred to as Fluorescent, Metal Halide, and Halogen-Fluorescent in that order.
When choosing an exposure unit there are several factors to address: speed, flexibility, resolution, and price. The better the light source the more expensive the unit will be.
Multi-point Exposure units- These units are most represented by the Fluorescent tube units on the market today. With there being multiple points of light, these units are best used for lower resolution images, spot color art work, and coarser halftones. These are the least expensive units and work excellent with diazo and photopolymer sensitive emulsions. Vacuum units will enhance the detail achieved with these types of units.
Combination Halogen-Fluorescent units are the next step up in exposure units. They can expose higher resolution halftones easier and work effectively with both photopolymer and dual cure emulsions.
Single point Metal Halide units use a single light source. This allows you to achieve extremely fine detail and the fastest exposure times. These are also the most expensive of the units. They come in varying wattages as well. This flexibility not only gives faster exposures, but lets you expose thicker emulsions easier and cleaner.