Re: motion picture, registration, & basic pinhole info

>bernard,
*For ASA, just use the one on the film can. For some color films, you
may need a filter and a little exposure correction for "reciprocity"
but I have shot long long exposures w/ B/W reversal, no troubles!
Call kodak's motion pic people at 1-800-621-3456 for more exact
reciprocity info (which filter, exposure compensation for which film
stock, etc,)

*As for registration, I don't think that you will get much of it by
simply turning the reel X-number of degrees. For one thing, the
diameter of the reel changes w/ more or less film on it.
I thought a little more about this dilemma and I thought more and
more about registration, I'm sure the pinhole camera can be
constructed, all in all, I think a better bet (much easier) is find
an old 16mm body, one that has "Bulb" mode such as a Bolex (look for
a Non-rex, it's cheaper and because you won't even use the reflex
feature anyway ) Now, remove the lens or body cap, stick your pinhole
aperture inside the "C"mount and go to town, start clicking
frames!!!! Costs a little cash but is NO LESS of a pinhole camera
than anything you construct. You will even get a frame counter (for
timing) and footage counter, you know when you're out of film this
way! If you do use a bolex, you could have the added bonus of a nice
litte rangefinder viewer (called an octameter) mounted to the side
of your camera. This is exactly what I intend to do with my camera.

*Here is info on how to determine f-stops focal length etc :
Pinhole plug-in formulas. (Metric & inches)
Easy to use....provided you have a calculator. It's been eons since
my last Algebra class, so, off of the top of my head, I couldn't
remember the formula for finding the square root of something if my
life depended on it.
Have you tried building that camera yet??

The size of hole you need depends on the kind of effect you want to
get. Many of us calculate the "optimum" size and then depart (or not)
from it, in order to experiment. There are many formulas to calculate
the "optimum" size. Optimum, in this case, means the hole that gives
the "sharpest" pictures. Incidentally, the sharpest pictures may or
may not be the "best" pictures for yo

SQR stands for square root.

mum pinhole diameter in inches =
0.0073 * SQR (focal length in inches)

For metric system the formula becomes:
Pinhole diameter = 0.03679 * SQR (focal length) where diameter and
focal length are in millimeters

Once you know the size of pinhole you will use, find the f/stop of
your camera by dividing the focal length by the diameter. Obviously,
both values must be in the same unit of measurement.

f/stop = focal length / diameter

More likely than not, the f/stop won't coincide with a full stop.
Since the progression of f/stops is not linear, to find where exactly
in between stops the f/stop of your pinhole camera is, you'll need a
mathematical formula to calculate it. But that isn't necessary due to
the "imprecise" nature of pinhole. I would suggest you approximate
the calculated f/stop to the next full stop (unless is really close
to lower one). The reason is that pinhole exposures are more likely
to be under than over-exposed.

Good luck Bernard, please let me know how that turns out (I'm an
animator myself)
Ed Gendron

>These two questions may be no-brainers to most here, but I'd appreciate
>some help:
>1. What is the surface area of slide film, 135 - 36? (Or the surface
>area of 120 or 220 - I don't even know what these numbers stand for.)
>2. Where can I get exposure times for pinhole cameras? (Is there a way
>to determine the ASA, or do I just use that of the roll I am loading?)
>Thanks.
>Bernie
>
>
>
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Edwin Gendron
Virginia Tech
Residential and Dining Programs Graphics
43 Owens Hall (0223)
Blacksburg, Va. 24061
(540)231-5398
egendron@vt.edu