A friend recently asked me about the need for a UV filter on a lens. Others have asked me about this in the past. It seemed like a good opportunity to write about it.
First and foremost, a UV filter can be seen as an insurance policy. A $20 piece of glass that protects $100s of glass.
You don’t have to adjust exposure or shutter speed for a UV filter in any conditions like you would for a polarizer or an ND filter. So basically, you can put it on your lens and leave it there. Other filters screw right on top of a UV filter. I buy a UV filter for every lens I have and leave them on the lens 24/7.
Besides the insurance, why use a UV filter? To my understanding, a cameras sensor (and even film) is sensitive to Red, Green and Blue light. UV light falls in the Blue end of non-visible light and the sensor is sensitive to light outside of the visible spectrum. That non-visible light can over-saturate the sensor and can often manifest as a blue cast over the image. This affect becomes more likely as you gain altitude as there is less atmosphere filtering the UV light. (more…)