The pinhole acts as the lens, the light being emitted outside the box is forced through the pinhole onto the photographic paper; which is able to record the image coming through the pinhole. However the image being recorded will project onto the paper as an inverted image (it will be upside down and back to front).
If you don’t understand here’s an illustration of the process
See the red lines are the light, because light only travels in a straight line the image becomes inverted.
Now whether the image is clear, detailed or comes through at all is to do with the exposure, i.e the amount of time you allow for light to enter the pinhole. The time will defer whether the image being recorded is inside or outside. Remember how the pinhole is the aperture, well that’s measured in increments called f-stops, that’s how you can work out how long you’ll need to lift the shutter to let the light travel through.
Here’s the calculation:
f-stop = distance from pinhole to paper (mm)
diameter of pinhole (mm)
So the distance from pinhole to paper, is exactly what it says; so you’re measuring (with the lid on if you have one) from the pinhole to where the photographic paper will lie.
Here’s my calculation:
f-stop = 104
0.8
We then use the combination of f-stop (f-130), film speed (6 ASA) to calculate the shutter speed (exposure time in seconds/minutes)
