Compound and Stereo- microscopes - how to determine the total magnification of a microscope
Initially, the camera obscura was, in fact, a room where the image was projected onto one of the walls through an opening in the opposite wall. It was used to observe the solar eclipse and to examine the laws of projection. It later became a portable instrument which was perfected with a converging lens. Instruments of this kind were often used as drawing aids and, at the dawn of photographic history, they formed the basis for the construction of the camera. The pinhole camera was finally also applied in modern science – during the mid-20th century scientists discovered that it could be used to photograph X-ray radiation and gamma rays, which the ordinary lens absorbs. As a result, the pinhole camera then found its way onto spacecraft and into space itself.
FresnelLight Bulb
Images created via a small opening will be found in the natural environment and in everyday life, and people in various parts of the world have been observing them since ancient times. Probably the earliest surviving description of this kind of observation dates from the 5th century BC, written by Chinese philosopher Mo Ti. In the Western hemisphere, Aristotle in 4 BC was asking, without receiving any satisfactory answer, why sunlight passing through quadrilaterals, for example, one of the holes in wickerwork, does not create an angled image, but a round one instead, and why the image of the solar eclipse passing through a sieve, the leaves of a tree or the gaps between crossed fingers creates a crescent on the ground. In 10 AD the Arabian physicist and mathematician Ibn al-Haitham, known as Alhazen, studied the reverse image formed by a tiny hole and indicated the rectilinear propagation of light. There was another scholar during the Middle Ages who was familiar with the principle of the camera obscura, namely the English monk, philosopher and scientist Roger Bacon. It was not until the manuscript Codex atlanticus (c. 1485) that the first detailed description of the pinhole camera was set down by Italian artist and inventor Leonardo da Vinci, who used it to study perspective.
Fresnellight lighthouse
Probably the earliest depiction of the camera obscura, published in the book De radio astronomico et geometrico liber in 1545. Here, Dutch physicist and mathematician Gemma Frisius described his observation of the solar eclipse in 1544. Johannes Kepler observed sun spots in the same way in Prague at the beginning of the 17th century; Kepler was also the first to use the term camera obscura.
The image created by a pinhole camera has certain characteristics which we won't find in classical lens photography. Since the process entails a central projection, the images in the pinhole camera are rendered in ideal perspective.
Fresnelstage light
The pinhole camera's simple construction offers a number of ways in which it can be constructed, using various materials. The cameras can be all kinds of shapes and sizes, with various formats and types of light-sensitive material, several holes, curved film planes, for panoramic images etc. There are all sorts of imaginative ways to make these cameras; the most ordinary of objects can unexpectedly become pinhole cameras, for example a matchbox, book, a pepper, travel bag, a delivery van, an old fridge or even a hotel room. You can, of course, turn your ordinary camera into a pinhole camera by simply replacing the lens with a small hole. And to complete the list, there are also a number of commercially produced pinhole cameras in existence, on the whole, highly elaborate models.
Many accessories can be added to Fresnels to further control their light. These are traditionally sold separately. However, some may be included with the new LED Fresnels (depending on the make and model).
Fresnellight pronunciation
Film set Fresnel lights are fairly simple tools and are quick to master. They come in various sizes and intensities and serve as a spotlight or a flood light. The apparatus itself is simple. A lamp (i.e., bulb) sits on a movable track behind a Fresnel lens and in front of a spherical reflector. The reflector directs most of the light towards the Fresnel lens, which then corrals the illumination into a beam.
If you’ve ever taken a film lighting class, you should know about a typical three-point lighting system. Often used for interviews, three or four Fresnels can act as a key light, a fill light, a rim/hair/backlight and the fourth as an optional background light. You’ve most likely seen the results of thousands of these setups in just about any documentary with a sit-down interview or in long-form news television shows, such as “60 Minutes.” But this isn’t all that you can do with a few of these lights. With the ability to up the intensity and direction for use in more artistic situations, you can create a moodier atmosphere.
Videomaker is always looking for talented, qualified writers. If you have a great idea you’d like to share with our readers, send it to editor@videomaker.com.
What you experience once you design, construct and try out your own pinhole camera is difficult to describe. You'll find yourself on a whole new plane of imagination, experimentation and creativity. Moreover, the photos themselves have an unusual atmosphere and capture the world in a different way than you are used to. Make your own pinhole camera and take some photographs with it. You'll find out for yourselves.
LEDFresnellight
Fresnel lights can be found in studios around the world because they are both portable and durable. They are incredibly useful for location shooting and deserve a spot in every professional’s setup. Let’s take a closer look at these lights and why they’re so important in video production today.
Diagram from 1685 showing how rays of light travel through the camera obscura, and how the size of the image depends on its distance from the hole, according to Johann Zahn.
Fresnel lights are also great for product shots where you need to light relatively small, immobile props from a distance. As mentioned earlier, many film stages will have a ceiling pipe grid filled with hanging Fresnels, usually controlled from a light board.
For more free tips on setting up your studio production, check out our ultimate guide to setting up a video production studio.
Partner with us to reach an enthusiastic audience of students, enthusiasts and professional videographers and filmmakers. Click here to contact a sales representative and request a media kit.
VintageFresnellight
Fair warning: Never touch a Fresnel’s glass lamp. It doesn’t matter if it’s hot or cold. Even when the lamp is cool, your fingers will leave a small amount of oil on the glass. This will heat up when the lamp is in use. This can cause the lamp to explode, and they aren’t cheap to replace. They can also leave a nasty burn if touched when hot. Seventy percent of the energy used by a tungsten light is dispersed as heat, with only 30 percent visible as light. Use gloves when handling any tungsten lights.
If you want to see what Fresnel lights are truly capable of, do an image search for George Hurrell and you’ll see beautiful portraits utilizing Fresnel lights dating back to the early twentieth century. You’ll find these workhorses of the lighting world on sets and on location across the world, making the movies, television and news shows we watch daily.
Fresnel lights have a lot of good points. But like with any tool, knowing its strengths and weaknesses can help you make the smartest choice. Fresnel lights, when used correctly and in the appropriate settings, can lead to truly cinematic, professional video.
Constructing a simple pinhole camera is easy. Make a hole in one side of a closable box made of material which doesn't let light in. Place a thin piece of metal or tin can with a tiny hole over the opening. On the outside of the box stick a strip of black tape over the opening which acts as the release. Then, in a dark room, attach a piece of film or photographic paper onto the opposite side and the camera is ready.
Augustin-Jean’s inspiration came from trying to reduce the weight of a large spherical lens. He did this by carving concentric rings — like the rings of a tree — in a flat lens. Each ring bends the light slightly more than the one beneath it. The results in the light rays all projecting as a beam. Outside of lighthouses and movie sets, Fresnel lenses are also used in car headlights and those large, outdoor event lights that shine into the night sky at movie premieres — like the one Commissioner Gordon uses to summon Batman.
Fresnel lights can be expensive. Also, learning how to use them takes time. So, it can be a tough investment to justify without prior experience with the lights. They can also be heavy, making them tricky to transport. These lights probably wouldn’t be a good choice for on-the-go productions or productions that need lights that are quick to set up and disassemble. They need some time to cool down before packing up, so fast-paced productions may find Fresnel lights hard to work with.
While the first photograph taken with a pinhole camera was the work of Scottish scientist Sir David Brewster back in 1850, the technique became more established in photography during the late 19th century when it was noted for the soft outlines it produced, as opposed to lenses generating perfect, sharp images. The pinhole camera was later abandoned and it wasn't until the end of the 1960s that several artists began using it in their experiments, thus awakening renewed interest in this simple photographic apparatus which endures to this day.
Fresnellight effect
As mentioned above, the image in the pinhole camera is created on the basis of the rectilinear propagation of light. Each point on the surface of an illuminated object reflects rays of light in all directions. The hole lets through a certain number of these rays which continue on their course until they meet the projection plane where they produce a reverse image of the object. Thus the point is not reproduced as a point, but as a small disc, resulting in an image which is slightly out of focus. This description would suggest that the smaller the hole, the sharper the image. However, light is essentially a wave phenomenon and so, as soon as the dimensions of the opening are commensurable with the dimensions of the light wavelength, diffraction occurs. In other words, if the hole is too small, the image will also be out of focus. The calculations for the optimal diameter of the hole in order to achieve the sharpest possible image were first proposed by Josef Petzval and later perfected by British Nobel prizewinner Lord Rayleigh (see Making the pinhole). He published the formula in his book Nature in 1891, and it is still valid today.
First off, Fresnel lights make things look really nice on camera. They can emit light that’s either soft or hard, so they are highly flexible lights. Most directors of photography (DPs) seem to prefer the color of tungsten Fresnel lights to newer LED lights, as well as the control the traditional lights allow. However, while DPs often prefer tungsten Fresnel lights, LED Fresnels draw much less power and stay cooler. LED fresnels are also dimmable and can even switch between daylight and indoor light in color within their single unit.
One of the most important things to know about a Fresnel light is how to pronounce it. There are few quicker ways to be labeled a “newb” (newbie, novice or newcomer) on a film set than by mispronouncing the light as FRAZ-nel. It’s pronounced “Fray-NEL,” with a silent “s.” The name for the light, or more accurately, the lens found in the lighting fixture, refers to the French engineer, Augustin-Jean Fresnel. He invented the technology for lighthouses in the early 1800s. His invention was so well received that he was nominated to be the commissioner of lighthouses in France.
A four-leaf barn door mounted to the front brackets of the light can control the beam, for example. Round scrims — metal screens mounted in a metal frame — can reduce light intensity. A speed ring with a softbox can help create a soft, wrap-around light. Traditional tungsten Fresnels don’t come with built-in dimmers, but external dimming systems cost about $50. Blackwrap(TM) or CineFoil(TM) — essentially heavy, black aluminum foil — is useful for shaping light. Attaching Gels and diffusion elements using C47s (a.k.a. wooden clothespins) to change the color or intensity of the light.
Another special characteristic is the infinite depth of field which, in a single photograph, allows objects to be captured with equal sharpness whether they are very close up or far away.
The pinhole camera takes in an extremely wide angle. The rays of light, however, take much longer to reach the edges of the negative than the centre, thus the picture is less exposed along the edges and therefore darkens.
Encasing all of this is a housing that dissipates the enormous amount of heat the unit produces. There is a knob, usually in the rear of the housing, which is used to move the lamp/reflector team along a track. This allows the beam to be either spotted or flooded. There are usually four brackets on the front of the light — three fixed and one movable. These brackets hold barn doors, speed rings, scrims and other tools. Finally, there is an AC power jack to provide electricity and a standard stand mount and yoke to mount the light to a light stand or ceiling pipe grid. Simple, right? Trust us, they’re even easier to use than we just explained.
FresnelLight price
A certain disadvantage of the pinhole camera is the amount of light allowed through (small aperture), which complicates and sometimes prevents entirely the photographing of moving subjects. Exposure time is normally counted in seconds or minutes but, in bad lighting conditions, this could be hours or even days (see Determining exposure times for pinhole cameras).
A pinhole camera, also known as camera obscura, or "dark chamber", is a simple optical imaging device in the shape of a closed box or chamber. In one of its sides is a small hole which, via the rectilinear propagation of light, creates an image of the outside space on the opposite side of the box.
* This is just a short summary of the most important stages of the development of the pinhole camera. One of the sources I used was the exhaustive account of the history of the pinhole camera in science and art presented by Eric Renner in his book Pinhole Photography, Rediscovering a Historic Technique (Focal Press 1995).