Re: Re: Building Pinhole Cameras
tomf2468@pipeline.com
Mon, 5 Aug 1996 17:23:32 GMT
Yes, a lot of people do use sewing needles to make a pinhole. I didn t
have access to a chart of sewing needles verses size when I started, so I
bought wire gauge drills. These are very small precision drills sold at
better hardware stores. Pinhole done by the numbers with correctly sized
holes onto an 8x10 negative, enlarged onto 16x20 silver gelatin paper was
almost as sharp as a 35mm neg enlarged onto 16x20 paper. That was not what
I was looking for. I wanted more error . So, I went to larger (1-1/2
or 2 times optimal ) pinholes, and I m much happier.
Three things seem to determine your resolution: One, focal length (I can t
make a high resolution long pinhole??). Two, hole size. The standard
formula is: Hole (inches)= square root of focal length/141, in mm=square
root of focal length/28.4. As stated earlier, I multiply this answer by 2
for wide angle pinholes and by 1.5 for normal angle pinholes. The larger
the pinhole, the softer the results (and the shorter the exposure!!).
Three, the quality of roundness in your pinhole, if the pinhole is
perfectly round (like the manufactured ones by Pinhole Resource or Edmunds)
it will be quite sharp, my wire gauge drills in thin brass shim stock
will be less sharp, and a sewing needle forced threw metal will be quite
unsharp (creates a rather ragged edged circle). I like my method (over
sized wire gauge drills and brass shim stock) because I get the soft effect
of a sewing needle type, with more speed (larger aperture). I also moved
down to a 4x5 negative, there wasn t any advantage to carrying the 8x10
around for my project.
Here are some typical drill sizes for 4x5 use:
Drill #80, hole size 0.00135 inches, 3.5 inch focal length, F260
Drill #77, hole size 0.018 inches, 6.5 inch focal length, F360
Drill #75, hole size 0.021 inches, 8.25 inch focal length, F390
Drill #70, hole size 0.028 inches, 14 inch focal length, F500
tomf2468@usa.pipeline.com (Tom Ferguson)
On Mon, Aug 5, 1996 6:22:36 PM, Macy Garcia wrote:
<SNIP>
>I remember just using a pin to make the hole. Is it any better to use a
>store bought "hole"?
>
>To much resolution? I was under the impression that the resolution wasn't
>as good as a lense?