Re: where 2 measure needle diameters?

----- Original Message -----
From: "Mike Keller" <Mike.Keller@wvculture.org>
> I tried that but wasn't sure I did it right. Care to elaborate on how you
> "measured?"

Sure, here is what you should do: Set your scanning to the highest optical
resolution (1200 in my case), scan the pinhole and then scan a transparent
ruler (use mm to make it easier). Using your favorite graphic program
(photoshop, corel, printshop, etc) "zoom in" the pinhole image as big as you
can get it and still be able to tell where the edges of the hole are (300%
in my case), then "zoom in" the ruler image the same amount you did for the
pinhole. You them measure the actual size of the pinhole on your computer
screen (I got 9mm), then do the same for a portion of the ruler seen on the
screen (I measured the screen image size of 5mm of the ruler and got 148mm),
that means each "computer screen millimeter" is equal to 5 / 148 or
0.03378 real millimeters, therefore 9 comp.screen millimeters will be equal
to: 9 x 0.03378 or 0.30402 real millimeters and that is equal to
0.30402 / 25.4 = 0.01196 inches. The same pinhole measured with my
0.0005" capable microscope, measures 0.012", close enough I'd say!.

Guillermo
Received on Tue Sep 12 14:44:36 2000