The frames-per-second question

It’s possible to capture video at high frame rates with a high speed camera like the MeltView SYNC (up to 1200fps), but is it worth it? First of all, it depends on whether you are watching welding in real-time or recording it for playback.

For real-time monitoring, the key question is, what is the top frame rate that the human visual system can perceive? For recording and playback, the key question is, how fast are the welding events that you want to observe happening?

We’ll consider live monitoring of welding in this post and recording and playback of welding in the next post.

According to Peter Jackson, when filming The Hobbit, his crew wanted to create a “more lifelike and comfortable viewing experience” by increasing the fps above the standard 24. He reports that they “tested both 48 fps and 60 fps. The difference between those speeds is almost impossible to detect, but the increase in quality over 24 fps is significant.” So they opted for 48 fps.

If you didn’t get to watch any of The Hobbit series in 48 fps, this app will help you to compare the difference that frame rate makes in the viewing experience.

First, slow the balls down to 50 px/s.
Notice the background – it does appear more lifelike at 48 fps than 24 fps.
Set one ball at 30 fps and the other at 60fps. Then begin to increase their speeds simultaneously to 100, then 200, then 500, etc.
You can also try setting the two balls at two different speeds to simulate a slower-moving object (e.g. the torch) and a faster-moving object (e.g. the molten metal).

For live monitoring of welding, does anything above 50 or 60 fps offer an advantage over 25 or 30 fps? There is a slight advantage in clarity, which may be noticeable for fast-moving processes such as GMAW or LBW (represented by speeds between 100-500 px/s in the simulation; note that at speeds of px/s <100 and >500, it’s hard to see any difference between 30 fps and 60 fps).

Perhaps more interesting to consider is what you can observe when you capture video at very high speeds, in the thousands of frames per second, e.g. for troubleshooting purposes. High speed imaging of welding is next.

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