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    Re: Vernier explanation
    From: David Pike
    Date: 2022 Jun 23, 02:55 -0700

    I spent most of the night wondering why my photographs were so unconvincing, especially the 5.6 one.  Was it just poor drawing, or was there another reason?  Well done those who spotted that I can no longer count to five.  Don’t tell my GP.  The other reason was parallax.  I folded the Vernier bit to make a stiffer, nicer edge.  That made it stand proud of the main scale causing a slight air gap.  As I held my smart phone quite close to take the photograph, parallax, a Greek trick on les Anglais this time arriving via France, must have come into play.  It couldn’t possibly have been my drawing.  I hope the attached photographs clear things up. 

    Having taught at times during my school master days both Practical Geometry and Tech Drawing to kids with varying thicknesses of spectacles, holding their heads at various heights above the paper from nose touching to high up, holding their rulers in all manner of fashions, it makes you realise that the different speeds of progress might not all have been due to individual mental ability.  Parallax might have been affecting some more than others.  DaveP

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