My understanding is that captchas were never supposed to be impenetrable, just difficult enough that to have bots (or mechanical turks) solve them at scale is expensive enough to deter that kind of automation. It’s probably getting a lot easier for a computer to solve nowadays though.

15/70 is the IMAX film format, using horizontal frames, 70 mm tall and 15 perforations across, in comparison to regular 70mm (large format) film which has much smaller frames turned vertically that are ~5 perforations tall.