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Difference between revisions of "Lenses"
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'''Plastic''' Less expensive lights usually have a flat plastic lens over the reflector and bulb (or LED). Plastic lenses are more resilient than glass and can be useful if the light will get knocked around and take some abuse. However, plastic is easier to scratch and often not as clear as glass. | '''Plastic''' Less expensive lights usually have a flat plastic lens over the reflector and bulb (or LED). Plastic lenses are more resilient than glass and can be useful if the light will get knocked around and take some abuse. However, plastic is easier to scratch and often not as clear as glass. | ||
'''Glass''' Glass lenses are more common in better lights. Borosilicate glass like Pyrex has lower thermal expansion than regular glass and therefore is less likely to crack when the lens is exposed to higher temperatures, like from an incandescent light. Tempered glass is heated and cooled to introduce stresses in the glass that make it stronger than regular glass, but it can not be ground after tempering. | [[File:Coatedlens.jpg|thumb|Less light is reflected off the coated lens at right than the uncoated lenses]]'''Glass''' Glass lenses are more common in better lights. Borosilicate glass like Pyrex has lower thermal expansion than regular glass and therefore is less likely to crack when the lens is exposed to higher temperatures, like from an incandescent light. Tempered glass is heated and cooled to introduce stresses in the glass that make it stronger than regular glass, but it can not be ground after tempering. | ||
'''Sapphire''' Another choice is a sapphire lens made of synthetic sapphire (not actually glass) which is stronger than tempered glass and very resistant to scratches. Due to it scratch resistance, sapphire is often used for watch crystals, but is also available as a flashlight lens. | '''Sapphire''' Another choice is a sapphire lens made of synthetic sapphire (not actually glass) which is stronger than tempered glass and very resistant to scratches. Due to it scratch resistance, sapphire is often used for watch crystals, but is also available as a flashlight lens. | ||