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I'm videoing rather than taking stills, but the same rules ought to apply and I'm hoping you might be able to suggest some things to try.

I want to video a weld in progress. The electric arc is very bright, so I have a welding mask in front of the camera lens. When viewed by eye it is possible to see detail of the end of the welding wire, but in the video the that detail is swamped by the light from the arc which overloads the CCD. I guess this is simply the difference in dynamic range between the human eye and the CCD.

The green channel maxes out first (I guess because the welding glass is green). Could you suggest a filter that would bring the channels more in balance? Apart from the green channel the overexposed blob remains about the same size until I go down 6 stops on exposure, so it might be worth concentrating on the green.

Another thought would be a heck of a lot of lighting. Two 500W halogen floodlights don't do much. I'm tempted to try to reflect some of the arc light onto the subject to brighten it up.

Any other thoughts on how to improve the image? The camera is a Sony CX115 and has manual settings. I've attached a couple of images at different exposures.

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well - first off, there are different grades of welding glass... There's actually a thread on here where people have used welding glasses for extremely long duration photography. Depending on the grade, the welding glass has at least 5 stops of extra attenuation (from a grade 9 to grade 13 glass) - As a first step, I'd try using a grade 13 welding glass - in my experiments, these are worth around 15 stops of light. Note: the grades of glass don't actually correspond to the ND filters stop values, a grade 10 welding glass is around 12 stops.
 
I've tried a few welding lenses. The photos are with an auto-darkening lens (it switches shade when it sees a bright light). I agree with the shade 13 - the lighter shades don't seem to work so well with the camera.

Fixed shade lenses are a bit better on colour, and I might end up using one, but the auto-darkening is useful for showing the torch position before the weld. Ideally I'd like to try an even darker shade as if I am to have that effect the difference between non-darkened and darkened needs to be huge to avoid the restriction of auto light metering. I might have to bodge it using a fixed shade filter I can quickly drop in.

Reflecting has to be worth a shot as I've got an awfully good light source there. I'll try that Monday.

It's really good to find a forum where people reply to you - thanks! :)
 
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