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
https://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 https://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 https://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
wanderlustcameras Posted 6 years ago.1
There are many factors involved. A lot of people tend to mention only one or two of the factors that effect sharpness. All of the following play an important roll.
1: Correct size of aperture (pinhole) for your specific focal length.
Each focal length has an optimum size. Too large and it will be softer than what is possible. Too small and it will be softer as well.
2: The precision of the hole (symmetry, no burs).
If you make a pinhole by hand, you create burs as you push the needle through the metal. These need to be sanded down. You also want to make sure the hole is as round and symmetrical as possible.
You can make a very good pinhole by hand with a little practice. The next best thing is micro drilled, then even better is laser drilled. The ultimate is a chemically etched pinhole. It is extremely precise and leaves the cleanest symmetrical hole in super thin metal.
3: Thickness of pinhole material
If the metal you are using is really thick the light has to pass through more material. This can increase the diffraction of light and soften the image a little more.
4: Film format
The larger the format you use, the sharper the image will look. The important thing to keep in mind is you must make legitimate comparisons. You can not compare a 35mm pinhole image to a 4x5 pinhole image. That is a loosing battle! It's like comparing grapes to watermelons. If you are making a 35mm film pinhole camera, compare it to other 35mm film pinhole images.
Standard 35mm image (24 x 36mm) = 864 sq. mm
Standard 4x5 film (101.6 x 127mm) = 12,903.2 sq. mm
So 4x5 has 14.934 times the image area.
The fact that you have to enlarge the 35mm pinhole image that much to equal a 4x5 image means it is not going to look as sharp.
5: Diffraction (this relates to film format)
A larger pinhole for a 4x5 camera is going to have less diffraction. A smaller pinhole for 35mm format will have more diffraction. This will start to soften the image. There is no way around this. Blame physics!
6: Film vs Digital
Film will look sharper than digital. The digital sensors have filters over them. This will bring the focus down a little bit.
7: Steady movement free setup.
A solid steady tripod is gonna give a crisp image compared to something wobbly.
8: Sharpening in Photoshop.
Who knows how much John Doe sharpened the image in photoshop after scanning the negative. If you are comparing your image to an image from someone online, keep this in mind.
9: Remember its pinhole
Sorry to geek out!