500mm pinhole camera "lens"

The focal length or projection length is determined by how far the pinhole is from the negative. In this case I have built a "tube" to have  the pinhole at 500mm from the negative.


The photographs are of Kingsnorth Power station taken from the shore line 3kms away the other side of the river.

As with pinhole camera the focus is soft but the depth of field is from in front of the camera to infinity.

A different view with closer foreground

The exposure was 6 minutes with a pinhole of 0.89mm giving an aperture of f/561.

The Calculation

I established the size of lens needed by measuring the width of the power station and the distance away on an Ordnance Survey map.  Then by the use of simple trigonometry I established the Tangent of the angle for half the width of the station. Knowing the half width of the image and now the Tangent of the angle I calculated the distance of  the lens to negative and made the necessary tube accordingly.  It created a photo exactly as expected.

A macro picture

On another web site, see link below, I have given a description as to how I make my pinholes. 
To make the size repeatable I have pushed the needle into a section of pencil rubber and the size required is the diameter of the needle at the surface of the rubber as measured by digital callipers.

The Nikon lens to take this photo was kindly loaned to me by Mike as it will be a rare thing that I need to take such close-ups.  The diameter of the needle poking through the rubber is only 0.28mm, the piece of rubber is about 5mm x 5mm  !!!

The needle is prepared ready to make the new pinhole "lens" for the film camera.

I am also building a monster 500mm "lens" for the 5x4" paper negative camera in an attempt to take telephoto photographs using a pinhole camera. The pinhole diameter for that will need to be 0.89mm quite the largest hole I have made.

LINK
http://www.darleys.pwp.blueyonder.co.uk/photography/

35mm Film pinhole camera tests

I decided not to give up so I prepared some photographic paper and popped it in the camera and closed over the eye piece .

 

The paper was exposed for 45minutes and then developed, scanned  at 1200dpi, mirror image and negative conversion and this is the result. 

I cannot see any fogging which I had previously experienced. The image is much sharper than when I tried to enlarge the previous negatives photographically. 

I have now stripped the camera apart again and  further improved the light prevention measures and a further test will be carried out ASAP.