From: "Bill T." 
To: atm{at}shore.net
Reply-To: "Bill T." 


One thing I noticed about an Edmund glass grating that I have is that the
black and clear lines are exactly the same width.  Looking at some flexible
film gratings, the black lines are little thin in proportion to the clear
lines, something like a 45/55 ratio.  Probably makes no difference, except
maybe if you're trying to do close match-ups with computer generated Ronchi
images.

Also, the edges of the lines on the glass plate are extremely straight,
whereas the edges of the film lines are a tiny bit bumpy.  FWIW, I only use
film gratings in my devices, the glass is just a curiosity on the shelf.

Bill T.

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