I guess there is not even such a filter that would actually be able to protect the sensors actually. Just like the guy said above, I guess Standard Clear Glass filter would actually be a great choice.
Not too sure about if that is true...?
Old topic, but as people allready pointed out, there are propper percision Bandpass-Filters available for Visible Light only, and people use them For Solar Photography, aka. Pointing a Highly Magnifying Lens / Mirror assembly (filling the Frame with the Incredibly bright sun) directly to the sun and even focusing on it, which would easily destroy the sensor and actually melt the Camera behind it and can even Start fires (has happened bevore to some people) without propper filters made for it. Given the use of High apperture Telescopes in combination with the Brightness of the Sun, there is WAY more power involved in solar photography than in your usual welding (dont know about some Extreme Indusrial applications, but for most other welding stuff and electric arcs this should hold true) with an common lens.
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those solar filters can sometimes be rather expensive, but they are very effective and have prooven themselves well over time, to be working very well, if you know what you are doing and get the Correct filter.
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Now i am no specialist about those Sensors at this, but from what i have seen and heard, they are way less delicate in terms of damage by non-visual Light in general compared to human eyes. As i said in my first reply, i shot Plasma Cutting (which can be watched by bare eyes but is still uncomftably bright and proppably also not good to look at for long time, a Second or so is fine however) and even CNC-Laser Cutting (dont know exactly which type of laser that was, but a invisible one, that could easily make you blind from the Smallest of reflection, and at that place i had to wear special Eye-Protection Glasses made for that Laser Wave-Length at all time the laser was running, shot that Laser for like 30-60 Min as a Closeup of the Actuall cutting from like 20cm distance for some Troubleshooting which they couldnt do propperly by themselves, because the Machine was just moving way to fast to propperly see what was even going on on the Cutting Head. Industrial Laser, with scary power.) without any protection besides some Clear glass filters to avoid the crazy hot Splashing of Metal beads hitting the Fontlens and also keeping all the Dust out of there, again, sometimes from Pretty close up. So as for usual Welding, i would expect, that as long as you can watch it by eyes, aka. from behind Welding Shades, it should be very save for a Camera sensor. As Long as not too much power and Heat is involved (like from some Crazy industrial Arc Lamps/ -furnace or industrial Welding), it might even be fine to shoot without any additional protection at smaller appertures, not too sure about Very fast lenses though. Back then for the Laser i just risked it, cause it was like a 400€ camera body only anyways, but wouldnt be sure if i would just go and try that with an Chronos again (without having tested with an cheap camera bevore, to know its save), as i completely expected to loose that camera on that day when shooting the Laser. But did survive just fine.
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If gyppor allready tried whatever he was shooting back then, maybe he could share what worked out for him as protection (if any at all).