Back then when people thought radiation was basically a vitamin, they crammed it into everything from face masks to toothpaste (Radium girls gives it a thumbs down), optics manufacturers weren't far behind (but hey, at least in their case it actually did something useful, Jiří Zouhar gives it a thumbs up).

To squeeze out a higher refractive index and cut down on dispersion (yeah, the photos looked a whole damn Röentgen better), they started making so-called lanthanum and earlier thorium glass - meaning the optical elements had lanthanum oxide (La₂O₃) or good ol' radioactive thorium dioxide (ThO₂) baked right into the glass mix. This wasn't just some coating like with anti-reflective layers, but an inseparable part of the glass mass itself where thorium content could reach up to 30%. Because of the radioactive decay of thorium isotopes, the Canadian balsam used for cementing lens elements would turn yellow over time, which, among other things, gave the photos a nice golden tint. The discoloration can be reversed by annealing the glass or exposing it to UV light - just stick it out in the sun, let it marinate for a while and voilà.

• Thorium in lenses was more commonly used from the 1940s to the 1970s, especially from Asahi, Kodak and Schneider-Kreuznach. Eventually it turned out thorium wouldn't actually kill you - but the fear of thorium definitely killed off thorium.
• Canada balsam (marginally also "Canadian turpentine") is a mixture of oil and resin obtained from the Balsam Fir (Abies balsamea). It is traditionally used, for example, as a medium for fixing laboratory specimens, as it is invisible when dry. When it is mixed in a 1:1 ratio with xylene, it produces a mixture with almost identical refractive index (which is very similar even without xylene) as a crown glass (n = 1.55). This is why it has found applications in the binding of lenses and optical systems. When you don't have anything to do during the long winter evenings and you feel like burning the mucous membranes or teasing the nervous system is the thing, I recommend opening a bottle of xylene.
• Today's lenses and optics are no longer cemented this way - UV fixation is used. It's an irreversible method (which can be a disadvantage, older lenses could be re-cemented by heat) and does not change over time, so you no longer encounter element separation caused by balm degradation.

Some lenses have emitted over 3 μSv/h, which is "not great, not terrible" - however, thorium emits "only" α and β radiation, so as long as you don't eat those lenses or roll around naked in them for long periods of time, you're fine. I guess. Either way, the lens is very nice, it just needs a really big camera or a really long bellows because of the long focal length. In any case - really big muscles. However, it's fun to work with and it's radiating joy and emmiting fun. Heh.

• Hear the truth: for every millimeter of your lens's focal length, you need just as many millimeters of bellows to focus at infinity. So, if you're rocking a Claron with a 610 mm focal length, you'll need at least 610 mm of bellows to even start playing the game. But wait - want to focus closer? That eats up more millimeters. Want a life-size 1:1 reproduction? Buckle up, because now you'll need double the extension - 1220 mm. That'll make you look like a badass even among accordion players.

• But wait, there's more! Your exposure is only accurate at infinity focus. The moment you extend the bellows, light starts vanishing like dreams and hopes. So you need to compensate - exposure correction for bellows extension. Then throw in filter factors. And just to kick you while you're down, Schwarzschild effect says hi. Well, welcome to j̶a̶c̶k̶a̶s̶s̶  large format.

Now let's get to the crux of the matter (emmiter?): the Claron. This thing sits in a monstrous Compound 5 shutter and when you slap it onto an 8x10" camera, it turns into a respectable telephoto with a full-frame equivalent focal length of about 89 mm. As mentioned earlier, this means you're gonna need loooong bellows and also strong back - see the photos below for evidence. Coverage-wise, this beast throws an image circle of up to 518 mm at infinity with an angle of view around 46°. That's obscene. The rendering is exactly what you'd expect from a process/repro lens: clinically sharp and contrasty as heck even wide open. Sure, f9 won't win any races in the speed department, but when paired with that long focal length and the sheer size of 8x10" and bigger, you still get a satisfyingly shallow depth of field. The subject pops cleanly from the background, enough to justify throwing around words like "plasticity" and "3D effect" without sounding like a complete tosser.

• Let's talk about the image circle. If it's too small, you'll end up with vignetting: dark corners, shadowy sides, or in the worst case scenario a sad little circular image floating in black like you used a bad lenshood. But if the coverage is generous enough (like here), the frame stays well-lit, sharp across the board and gives you plenty of wiggle room for all those glorious camera movements - tilts, shifts, swings and whatever will row your boat.