Re: pinhole size

Hi:

Its not exact but close enough. I have a 10x loup (a small magnifier) and
a metal ruler incremented in .5 mm, both bought from a hardware tool
supply shop.

When I make a pinhole I can check to see if its round with this and get an
accurate enough idea of the pinhole's diamter by holding the ruler up to
the pinhole and looking at it through the loup. With the ruler and its .5
mm increments I can judge the size of the pinhole accurate to 1/10 of a
millimeter. Not rocket science but accurate enough.

The ruler and loup were under $20.00.

Another option is to find a comparator, (a loup with a scale - called a
reticle) or something like a linen tester see
http://www.edmundoptics.com/IOD/DisplayProduct.cfm?productid=1600

or one could use just the reticle with an existing loup.

A reticle is a small piece of glass or film with a scale etched on the
surface - for measuring small things under some kind of magnifier

http://www.edmundoptics.com/IOD/DisplayProduct.cfm?productid=1728

These from edmund optics are expensive, but something similar could likely
be found cheaper

One could gamble with these:

http://www.sciplus.com/singleItem.cfm?terms=2668

an assortment 10 of surplus reticles

On Sun, 21 Jul 2002, William Erickson wrote:

> One simple way is to photograph the pinhole over a light box with a ruler
> beside it, then enlarge the negative as big as you can and compare the
> diamter of.the aperture with distance on the ruler. Comparators for threads
> are said to work fairly well. I bought a set of pre-drilled pinholes and use
> them for eyeball comparison.
>
> ----- Original Message -----
> From: "Jean Hanson" <jhanson@pon.net>
> To: <pinhole-discussion@pinhole.com>
> Sent: Sunday, July 21, 2002 5:53 PM
> Subject: [pinhole-discussion] pinhole size
>
>
> > I have the math on how to figure the ideal size of the pinholes but how
> > do you actually measure them. Does everyone but me have a microscope, a
> > micrometer? what? Jean
> >
> >
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>
>
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---------------------------------------------------------
Gordon J. Holtslander Dept. of Biology
holtsg@duke.usask.ca 112 Science Place
http://duke.usask.ca/~holtsg University of Saskatchewan
Tel (306) 966-4433 Saskatoon, Saskatchewan
Fax (306) 966-4461 Canada S7N 5E2
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Received on Sun Jul 21 22:38:57 2002