PINHOLE CAMERA What do we need to know? Light travels in straight lines A pinhole is a tiny hole

Camera Obscura Camera Obscura (latin) > Dark Room Projects a view of the outside onto the inside walls The image is upside down

Collecting Place / Locked Treasure Room The history… 5th Century BC: Mo-Ti 322 BC: Aristotle 965 AC: Alhazen 1500s: Leonardo Da Vinci Collecting Place / Locked Treasure Room

Pinhole: Bright Object Light reflects off bright surface Small Hole >> Sharper Image Bigger Hole >>Brighter Image Bright Object Light reflects off bright surface Pass through small holes Light rays cross Upside down image on wall Small Hole

The history… Used for observing eclipses 1558 > Lenses and mirrors Leonardo Da Vinci: "When images of illuminated objects ... penetrate through a small hole into a very dark room ... you will see [on the opposite wall] these objects in their proper form and color, reduced in size ... in a reversed position, owing to the intersection of the rays". Leonardo da Vinci Used for observing eclipses 1558 > Lenses and mirrors

1558 1568 1700 1728 1558: Lens Based Camera Obscura, 1568 Correct for reversed image 1568 1700: Hooke described ‘picture box’ in a paper to the Royal Society 1700 1728: Reversed the specimen to overcome upside down image 1728

The history… 1700 – 1900 1898 1970 Silicon Image Detector, 1970 Translucent screen + 45° mirror: Override two inversions of image But here’s the puzzle. How could the images projected by the camera obscura stir up the emotions and widen the horizon of visual experiences of the likes of Huygens and, later on, Vermeer? After all, versions of this instrument had been around long before this period. The pinhole camera, for example, was known and used in classical antiquity in an astronomical setting, particularly for observing solar eclipses. From antiquity up to the Renaissance, the camera obscura never fell into total oblivion. Now and then, it was mentioned and occasionally used, mostly for astronomy. But it did not attract very much attention. At the end of the 16th century, however, its fortunes changed dramatically. The pinhole camera obscura was equipped with lenses and mirrors and transformed into the optical camera obscura of the early modern period. 4 Although no single optical camera obscura has survived from the 17th century, we know from written sources and a few book illustrations that at least four principal types of this camera were developed and in use. The simplest arrangement, with a lens fastened in the pinhole, projected an inversed and reversed image on a vertical screen opposite the aperture. A variation on this employed a translucent screen, allowing the viewer to see the image from the other side, thereby correcting the left-to-right reversal. These two types of camera projected the image directly and could be combined in one device. There were at least two additional incarnations of the camera obscura, which used a mirror oriented at 45 degrees to the path of light to achieve vertical reversion. Without a translucent screen the projected image remained horizontally reversed, but with a translucent screen this too could be overcome (Figure 2). Judging from contemporary illustrations, standardized forms of these four types were slow to replace makeshift, ad hoc constructions put together on site to meet a specific need. If the earliest optical camera obscuras were indeed temporary devices, this could explain why none appears to have survived. 1898 Silicon Image Detector, 1970 1970

Digital Cameras/ SLR The history… 1888 Kodak handheld camera 1959 Camera sent back to Kodak for processing Digital Cameras/ SLR Reflect IR beam off subject + focus lens http://www.mpiwg-berlin.mpg.de/Preprints/P333.PDF But here’s the puzzle. How could the images projected by the camera obscura stir up the emotions and widen the horizon of visual experiences of the likes of Huygens and, later on, Vermeer? After all, versions of this instrument had been around long before this period. The pinhole camera, for example, was known and used in classical antiquity in an astronomical setting, particularly for observing solar eclipses. From antiquity up to the Renaissance, the camera obscura never fell into total oblivion. Now and then, it was mentioned and occasionally used, mostly for astronomy. But it did not attract very much attention. At the end of the 16th century, however, its fortunes changed dramatically. The pinhole camera obscura was equipped with lenses and mirrors and transformed into the optical camera obscura of the early modern period. 4 Although no single optical camera obscura has survived from the 17th century, we know from written sources and a few book illustrations that at least four principal types of this camera were developed and in use. The simplest arrangement, with a lens fastened in the pinhole, projected an inversed and reversed image on a vertical screen opposite the aperture. A variation on this employed a translucent screen, allowing the viewer to see the image from the other side, thereby correcting the left-to-right reversal. These two types of camera projected the image directly and could be combined in one device. There were at least two additional incarnations of the camera obscura, which used a mirror oriented at 45 degrees to the path of light to achieve vertical reversion. Without a translucent screen the projected image remained horizontally reversed, but with a translucent screen this too could be overcome (Figure 2). Judging from contemporary illustrations, standardized forms of these four types were slow to replace makeshift, ad hoc constructions put together on site to meet a specific need. If the earliest optical camera obscuras were indeed temporary devices, this could explain why none appears to have survived. 1959 J-Phone: Cost: $ 500 110,000 pixels (0.1 MP) 2000

Ray diagrams:

Making a pinhole camera … It can be very simple! Dark box or tube + a tiny hole in the front We’ll use a screen for viewing on the back instead of film

STEp 1 Roll a tube of black card OR make a box with two open ends

STEp 2 Use the tinfoil to cover one end (Blocks light from entering)

STEp 3 Make a tiny pinhole in the front

STEp 4 4 Add a screen to the back The image will appear here

STEp 5 The image will be dark so you’ll need to cover the screen Make a cover that wraps around the screen.

TEST IT!

STAR

SUN

Problems with pinholes image plane effective focal length, f’ optical axis y x z pinhole

Problems with pinholes Pinhole size (aperture) must be “very small” to obtain a clear image. However, as pinhole size is made smaller, less light is received by image plane. If pinhole is comparable to wavelength of incoming light, DIFFRACTION effects blur the image! Sharpest image is obtained when: pinhole diameter Example: If f’ = 50mm, λ = 600nm (red), d = 0.36mm

Image Formation using (Thin) Lenses Lenses are used to avoid problems with pinholes. Ideal Lens: Same projection as pinhole but gathers more light! i o Gaussian Lens Formula: f is the focal length of the lens – determines the lens’s ability to bend (refract) light f different from the effective focal length f’ discussed before! P P’ f

Two Lens System Rule : Image formed by first lens is the object for the second lens. Ray passing through focus emerges parallel to optical axis. Ray through optical center passes un-deviated. image plane lens 2 lens 1 object intermediate virtual image final Magnification:

The Eye The human eye is a camera! Iris - colored annulus with radial muscles Pupil - the hole (aperture) whose size is controlled by the iris Photoreceptor cells (rods and cones) in the retina

PINHOLE CAMERA How to Build It