Thoriated photography lenses #thorium

You know how sometimes you stumble upon something totally unexpected? Well, I recently got really curious about those 'thoriated lenses' I kept hearing about. My initial thought was, 'Wait, my camera lens could be radioactive?' It sounded like something out of a sci-fi movie! But as I dove deeper, especially after seeing discussions about whether a modern cell phone sets off a geiger counter (spoiler: it usually doesn't!), I realized this was a fascinating corner of physics. The original article mentioned how these vintage lenses, especially the really high-quality ones, sometimes contained thorium. And yes, they absolutely could set off a radiation alarm! The reason boils down to thorium's unique properties. This element, a naturally occurring radioactive metal, was used because it gave lenses an incredibly high refractive index. This meant photographers could achieve exceptionally good photography with sharper images and better color correction – a huge advantage back in the day. The trade-off? A tiny bit of radioactivity. So, what about being a 'thorium reader'? This is where a geiger counter comes in handy. If you have an old lens and you're curious, a geiger counter is the classic tool to detect ionizing radiation. You simply hold it near the lens, and if there's thorium present, you'll hear those characteristic clicks. It’s quite an experience to hear your camera gear making a radiation detector chirp! Associate Professor Robert B. Hayes, PhD, even mentioned how these lenses were known to trigger alarms. Now, before you panic and throw out your vintage gear, it's important to understand the levels. The radiation from thoriated lenses is generally considered low-level. Most experts agree that the risk to a photographer using these lenses occasionally is minimal, especially since the alpha particles emitted by thorium are easily stopped by the lens glass itself. The main concern might be if you're collecting dozens of these lenses and storing them in an unventilated space for extended periods, or if the thorium somehow becomes airborne (which is highly unlikely with intact lenses). How can you tell if your lens is thoriated without a geiger counter? It's tricky. Some lenses developed a yellowish or brownish tint over time, often called 'yellowing' or 'browning,' due to the radiation affecting the glass. This is a common indicator, but not all yellowed lenses are thoriated, and not all thoriated lenses yellow significantly. Researching specific lens models is your best bet! Many online communities have lists of known thoriated lenses. While modern lenses have moved away from thorium, using safer alternatives to achieve that high refractive index, it's a cool piece of photographic history. It just goes to show how science and engineering constantly evolve! So, if you're ever at a flea market and spot an old, suspiciously yellowed lens, you might be looking at a piece of photographic history that could indeed get a geiger counter buzzing. It's a fun fact to share with your fellow photography enthusiasts!