When using IPL we consider the condition we are treating, or trying to eradicate (whether this is unwanted hair, unwanted pigmentation, broken capillaries etc.), as the target. We apply filters to the light the IPL equipment is emitting (420 nm – 1200 nm) to reduce the wavelength range of the light.

For example if we use a filter with a range of 640 nm – 1200 nm it will block all light wavelengths 420 nm – 639 nm, letting through only 640 nm – 1200 nm. This particular filter is used when hair (the bulb or root at the base of the hair shaft) is the target. The reason we filter out certain wavelengths is because they have no effect on the target, so leaving them in has no benefit, we leave only the wavelengths that focus on the target.