True prismatic letters are a work of art. Simulated prismatic letters are much easier to make and less expensive. The simulated prismatic are often acceptable, especially with the existence of so many graphics software programs like Corel and Adobe Illustrator. When you use these to generate a “prismatic” letter, the effect is actually simulated. Many people today cannot tell the difference.
With a true prismatic letter, the high center edge will be at a consistent height. For example, a 2” thick prismatic letter will be 2” thick all along its center lines. To achieve this with a Roman (or thick and thin stroke) letter requires that the “beveled” edge from the peak down to the base of the letter will vary in angle. The thin strokes of the letter will have very steep bevels, whereas the heavy strokes will have flatter bevels.
Since a standard CNC machine will be using a bit with a fixed angle, it is impossible for it to produce true prismatic letters. These are generally carved by hand. Obviously, this makes them more expensive, but a true prismatic letter, well made and gold leafed, is just about the pinnacle of the sign crafters art.
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