I’m told that to photograph the solar eclipse with my smartphone I will need a filter to put in front of my camera to prevent damage to the sensor. My understanding, and maybe this is where I’m wrong, is that a camera that doesn’t have a telephoto lens can shoot pictures of the sun on a normal day without a filter. If that’s true what makes a solar eclipse different? It would seem to be like the more the sun gets blocked, the less energy makes it to the sensor, the safer it is for the electronics. Does it have to do with exposure time due to a darker scene?
In: Physics
Your camera (and your eyes) incorporates a light sensor. Normally, if you point either at the sun, it detects a ton of light and immediately works to close the aperture (or, for your body, your iris contracts and you reflexively want to look away or cover your eyes.) That reduces how much light is coming through the lens and protects the sensor/your retinas.
During the eclipse, not as much visible light will be hitting the sensor/your eye. This makes them think it’s dark, so the aperture/iris opens to let more light in.
UNFORTUNATELY, visible light is only PART of the sun’s energy. It’s still emitting a lot of UV light, and even during the eclipse it’s enough to cause damage. Worse: a camera lens focuses light onto the sensor, think about that like an amplifier. So this creates a big problem: there is a dangerous amount of UV light, but the camera has been tricked into *letting more in*, and the lens is focusing it on the sensor. That’s more likely to cause damage. Same thing happens with your eyes: you end up staring at a source of powerful UV energy without the normal defenses that would prevent you from doing that.
A good example of what happens took place at a fancy party for crypto people recently. The party organizers wanted UV black lights. Somehow they found some exceptionally powerful ones meant for sterilizing things, not for air, and decided to install those. Many of the attendees got sick and experienced at least temporary blindness after being exposed to extremely harmful levels of UV light. Nobody knew it was dangerous because our bodies aren’t used to a nature where we can get blasted by UV without ALSO sensing a lot of visible light and/or heat.
That’s why the filters are OK (if they are good ones). They block the invisible UV light and a very large portion of the visible light so that it’s safe to look at the sun even if your camera/eyeballs are confused and think it’s a dim object.
Latest Answers