Interesting device... anyway this is to measure frequency, not elongation.
There are also mobile apps to measure vibration by reading internal accelemeters, I use this one https://web.archive.org/web/20180430...ensor&hl=en_US
Search "vibration meters"...
... but IMHO the laser it's essential to acknowledge the real impact of the vibration on film, because we can simply ponderate vibration we see in the spot according to the magnification, this pretty intuitive, and we also can make straight calcualtions to have a quantitative value.
The vibration frequency is useful to know at what shutter speed we may start freezing the vibration, ...if we expose only during 1/10 of the typical vibration cycle then we may have 1/5 of the blur radius than with a long exposure.
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