Notes for personal use. You can click the links and maybe find something useful for yourself too.
From wikipedia: https://en.wikipedia.org/wiki/Pinhole_camera
A pinhole camera is a simple camera without a lens but with a tiny aperture, a pinhole – effectively a light-proof box with a small hole in one side. Light from a scene passes through the aperture and projects an inverted image on the opposite side of the box, which is known as the camera obscura effect.
to make a camera yourself all you need is a light tight box. Your lens is on one side of this box and the sensor? that's the film negative. But why try a pinhole camera?
A tiny pinhole won't let through a lot of light. This is an effect you can play with: because it takes longer to get a correct exposure, all movement in your photo will smooth out. A tree in the background will move the entire 2 min you are taking your picture.
Characteristics of pinhole camera photography Pinhole photographs have nearly infinite depth of field, everything appears in focus. As there's no lens distortion, wide angle images remain absolutely rectilinear. Exposure times are usually long, resulting in motion blur around moving objects and the absence of objects that moved too fast. Other special features can be built into pinhole cameras such as the ability to take double images by using multiple pinholes, or the ability to take pictures in cylindrical or spherical perspective by curving the film plane.
Single Hole Pinhole Camera
Calculate 6x9 Max angle of view
http://www.mrpinhole.com/calcpinh.php Using mrpinhole calculator, find the widest angle without vignetting (where the image circle becomes too small to cover the negative)
52mm (~ 20mm-25mm 35mm equivalent),
173 f - 0.3 pinhole diameter, image diameter 99,8 mm 100mm img diagonal of 6x9, 87,8 deg Angle of view 125 film speed, 1/2 sec sunny day exposure
F/173 exposure guide http://www.mrpinhole.com/exposure.php?Fstop=173 Determining Exposure Times for Pinhole Cameras [pinhole.cz]
Angle of View
https://skweres.net/CalcDoc/AngleOfView.html The angle of view defines the image boundaries of the subject. An 40 degree angle is considered normal, more than 50 degrees is wide angle and less than 20 degrees is telephoto. the wider the angle of course, the more uneven the illumination of the negative.
https://digital-photography-school.com/wide-angle-lenses-landscape/ https://gizmodo.com/5911493/the-lens-explained-telephoto-vs--wide-angle wide angle makes the horizon seem further away, long lenses compresses perspective, making it look as if things are closer together
https://www.photo.net/discuss/threads/normal-lens-for-a-camera-with-a-4in-by-5in.172519/ leonard_evens, Sep 28, 2006
Since it comes up so often in large format photography, every large format photographer should understand the Pythagorean theorem. That says that if you have a rectangle, the diagonal, i.e., the distance between opposite corners, is found as follows. Square each side of the rectangle, and then add. Finally take the square root of that sum. This can be done easily on almost any calculator which has both a square key and a square root key. As Michael pointed out, the usable area of a 4 x5 frame has dimensions 95 x 120 mm. Using my computer's built in calculator, I find 95 squared = 9025, 120 squared = 14400. The sum is 23425. the square root of that is 153.05227865, but we would normally ignore anything past the first three digits and simply take the answer as 153 mm, which is close enough.
Optimal pinhole Diameter
The sharpest image is obtained at the optimal diameter for a given focal length. This is due to a trade off between flare and fuzziness. As hole size is increased the picture becomes fuzzier. As hole size is decreased the picture becomes sharper up to a point where flare becomes a problem. There are many opinions on the exact formula used to determine this, however, most are derived from the equation: optimal diameter = square root (wavelength focal length k) * 2 k is set between 0.5 and 1
What is a normal lens on a 6x9 negative?
1.50:1 56 × 84 8 exposures
THE IDEAL PINHOLE http://pinhole.stanford.edu/ip.html
56^2 + 84^2 3.136+7.056 = 10.192 √10.192 = 100.9554357129917
100mm is a normal lens
f number In order to set exposure times, you have to know the f number of the pinhole camera. This is calculated simply by dividing the focal length by the diameter of the hole. However, it is important to bear in mind that, during longer exposures, the time must be extended due to reciprocity failure
52 / 0,3 = f173,3333333333
- Set your light meter to the film's ISO/ASA
- Take a reading
- Locate the line that your reading is on
- Read across the right hand column for your exposure time
- Add time for reciprocity failure
Some thoughts and things; on keeping a small notebooks in an ‘always carry a sketchbook’ - kind of way. Drawing for fun, not so much to study.