Many films contain a top supercoat layer to protect the emulsion layers from damage. [24] Some manufacturers manufacture their films with daylight, tungsten (named after the tungsten filament of incandescent and halogen lamps) or fluorescent lighting in mind, recommending the use of lens filters, light meters and test shots in some situations to maintain color balance, or by recommending the division of the ISO value of the film by the distance of the subject from the camera to get an appropriate f-number value to be set in the lens. [25] [26]

When a photograph is cut in half, each piece shows half of the scene. When a hologram is cut in half, the whole scene can still be seen in each piece. This is because, whereas each point in a photograph only represents light scattered from a single point in the scene, each point on a holographic recording includes information about light scattered from every point in the scene. It can be thought of as viewing a street outside a house through a 120cm ×120cm (4ft ×4ft) window, then through a 60cm ×120cm (2ft ×4ft) window. One can see all of the same things through the smaller window (by moving the head to change the viewing angle), but the viewer can see more at once through the 120cm (4ft) window. Silver halide photographic emulsion and photographic material containing the same". Archived from the original on 2021-06-19 . Retrieved 2020-08-16. A diffraction grating is a structure with a repeating pattern. A simple example is a metal plate with slits cut at regular intervals. A light wave that is incident on a grating is split into several waves; the direction of these diffracted waves is determined by the grating spacing and the wavelength of the light. The holograms you can buy as novelties or see on your driver's license are reflection holograms. These are usually mass-produced using a stamping method. When you develop a holographic emulsion, the surface of the emulsion collapses as the silver halide grains are reduced to pure silver. This changes the texture of the emulsion's surface. A hologram is made by superimposing a second wavefront (normally called the reference beam) on the wavefront of interest, generating an interference pattern which is recorded on a physical medium. When only the second wavefront illuminates the interference pattern, it is diffracted to recreate the original wavefront. Holograms can also be computer-generated by modelling the two wavefronts and combining them digitally. The resulting digital image is then printed onto a suitable mask or film and illuminated by a suitable source to reconstruct the wavefront of interest.

Different transparencies

Day Lance McNeil Ian (2002). Biographical Dictionary of the History of Technology. Routledge. p.631. ISBN 1-134-65020-5. In contrast, a hologram encodes both the brightness and phase of each light wave. That combination delivers a truer depiction of a scene’s parallax and depth. So, while a photograph of Monet’s “Water Lilies” can highlight the paintings’ color palate, a hologram can bring the work to life, rendering the unique 3D texture of each brush stroke. But despite their realism, holograms are a challenge to make and share. To record a hologram of a complex object, a laser beam is first split into two beams of light. One beam illuminates the object, which then scatters light onto the recording medium. According to diffraction theory, each point in the object acts as a point source of light so the recording medium can be considered to be illuminated by a set of point sources located at varying distances from the medium. Most films are affected by the physics of silver grain activation (which sets a minimum amount of light required to expose a single grain) and by the statistics of random grain activation by photons. The film requires a minimum amount of light before it begins to expose, and then responds by progressive darkening over a wide dynamic range of exposure until all of the grains are exposed, and the film achieves (after development) its maximum optical density.

Common film speeds include ISO 25, 50, 64, 100, 160, 200, 400, 800, 1600, 3200, and 6400. Consumer print films are usually in the ISO 100 to ISO 800 range. Some films, like Kodak's Technical Pan, [28] are not ISO rated and therefore careful examination of the film's properties must be made by the photographer before exposure and development. ISO 25 film is very "slow", as it requires much more exposure to produce a usable image than "fast" ISO 800 film. Films of ISO 800 and greater are thus better suited to low-light situations and action shots (where the short exposure time limits the total light received). The benefit of slower film is that it usually has finer grain and better color rendition than fast film. Professional photographers of static subjects such as portraits or landscapes usually seek these qualities, and therefore require a tripod to stabilize the camera for a longer exposure. A professional photographing subjects such as rapidly moving sports or in low-light conditions will inevitably choose a faster film. This may sound far-fetched, but you encounter this phenomenon every day. Every time you look in a mirror, you see yourself and the surroundings behind you as though they were on the other side of the mirror's surface. But the light rays that make this image aren't on the other side of the mirror — they're the ones that bounce off of the mirror's surface and reach your eyes. Most holograms also act like color filters, so you see the object as the same color as the laser used in its creation rather than its natural color. Sensitivity across the visible spectrum means you don't need different film for different lasers. And if you want to make full-color holograms, expose with multiple wavelengths in one material! Real Holograms Basic Sensitometry and Characteristics of Film" (PDF). Kodak Cinema and Television: Technical Information. Kodak. Archived (PDF) from the original on 5 March 2016 . Retrieved 11 August 2015.

The emulsion layers of films are made by dissolving pure silver in nitric acid to form silver nitrate crystals, which are mixed with other chemicals to form silver halide grains, which are then suspended in gelatin and applied to the film base. The size and hence the light sensitivity of these grains determines the speed of the film; since films contain real silver (as silver halide), faster films with larger crystals are more expensive and potentially subject to variations in the price of silver metal. Also, faster films have more grain, since the grains (crystals) are larger. Each crystal is often 0.2 to 2 microns in size; in color films, the dye clouds that form around the silver halide crystals are often 25 microns across. [16] The crystals can be shaped as cubes, flat rectangles, tetradecadedra, [17] or be flat and resemble a triangle with or without clipped edges; this type of crystal is known as a T-grain crystal or a tabular grain (T-grains). Films using T-grains are more sensitive to light without using more silver halide since they increase the surface area exposed to light by making the crystals flatter and larger in footprint instead of simply increasing their volume. [18] a b Peres, Michael R. (2008). The concise Focal encyclopedia of photography: from the first photo on paper to the digital revolution. Burlington, Mass.: Focal Press/Elsevier. p.75. ISBN 978-0-240-80998-4. KODAK PROFESSIONAL Technical Pan Film Technical Data Sheet" (PDF). Eastman Kodak Company. Archived (PDF) from the original on 17 August 2000 . Retrieved 13 August 2015.

If parts of the image are exposed heavily enough to approach the maximum density possible for a print film, then they will begin losing the ability to show tonal variations in the final print. Usually those areas will be considered overexposed and will appear as featureless white on the print. Some subject matter is tolerant of very heavy exposure. For example, sources of brilliant light, such as a light bulb or the sun, generally appear best as a featureless white on the print. A typical lens-based photograph encodes the brightness of each light wave — a photo can faithfully reproduce a scene’s colors, but it ultimately yields a flat image.Like conventional photography, holography requires an appropriate exposure time to correctly affect the recording medium. Unlike conventional photography, during the exposure the light source, the optical elements, the recording medium, and the subject must all remain motionless relative to each other, to within about a quarter of the wavelength of the light, or the interference pattern will be blurred and the hologram spoiled. With living subjects and some unstable materials, that is only possible if a very intense and extremely brief pulse of laser light is used, a hazardous procedure which is rarely done outside of scientific and industrial laboratory settings. Exposures lasting several seconds to several minutes, using a much lower-powered continuously operating laser, are typical. This section does not cite any sources. Please help improve this section by adding citations to reliable sources. Unsourced material may be challenged and removed. ( October 2016) ( Learn how and when to remove this template message) Holographic film: Holographic film can record light at a very high resolution, which is necessary for creating a hologram. It's a layer of light-sensitive compounds on a transparent surface, like photographic film. The difference between holographic and photographic film is that holographic film has to be able to record very small changes in light that take place over microscopic distances. In other words, it needs to have a very fine grain. In some cases, holograms that use a red laser rely on emulsions that respond most strongly to red light. A hologram can be made by shining part of the light beam directly into the recording medium, and the other part onto the object in such a way that some of the scattered light falls onto the recording medium. A more flexible arrangement for recording a hologram requires the laser beam to be aimed through a series of elements that change it in different ways. The first element is a beam splitter that divides the beam into two identical beams, each aimed in different directions: Vitale, Tim (March 2006), Film Grain, Resolution and Fundamental Film Particles (PDF), archived (PDF) from the original on 2020-06-05 , retrieved 2020-08-15

Color reversal film produces positive transparencies, also known as diapositives. Transparencies can be reviewed with the aid of a magnifying loupe and a lightbox. If mounted in small metal, plastic or cardboard frames for use in a slide projector or slide viewer they are commonly called slides. Reversal film is often marketed as "slide film". Large-format color reversal sheet film is used by some professional photographers, typically to originate very-high-resolution imagery for digital scanning into color separations for mass photomechanical reproduction. Photographic prints can be produced from reversal film transparencies, but positive-to-positive print materials for doing this directly (e.g. Ektachrome paper, Cibachrome/Ilfochrome) have all been discontinued, so it now requires the use of an internegative to convert the positive transparency image into a negative transparency, which is then printed as a positive print. [5] Japan-based Fujifilm's instant film "Instax" cameras and paper have also proven to be very successful, and have replaced traditional photographic films as Fujifilm's main film products, while they continue to offer traditional photographic films in various formats and types. [59] Reusable film [ edit ] This missing key is provided later by shining a laser, identical to the one used to record the hologram, onto the developed film. When this beam illuminates the hologram, it is diffracted by the hologram's surface pattern. This produces a light field identical to the one originally produced by the scene and scattered onto the hologram. Kodak Ektachrome E100 Film is Now Available in 120 and 4x5 Formats". petapixel.com. 10 December 2019. Archived from the original on 2020-06-03 . Retrieved 2020-06-03.When a plane wave-front illuminates a negative lens, it is expanded into a wave that appears to diverge from the focal point of the lens. Thus, when the recorded pattern is illuminated with the original plane wave, some of the light is diffracted into a diverging beam equivalent to the original spherical wave; a holographic recording of the point source has been created. Although cellulose acetate or " safety film" had been introduced by Kodak in 1908, [45] at first it found only a few special applications as an alternative to the hazardous nitrate film, which had the advantages of being considerably tougher, slightly more transparent, and cheaper. The changeover was completed for X-ray films in 1933, but although safety film was always used for 16mm and 8mm home movies, nitrate film remained standard for theatrical 35mm films until it was finally discontinued in 1951. [46] You will see different images and the colors depending upon the position and angle from which you are looking at the film. The image and spectral coloring will change as you view the grooves at different positions and from different angles. Many holographic films are metallized with Aluminum. Not only does this protect the embossed surface and reflect light through it, it also provides a more colorful, crisp and bright image. Holography film is widely used for brand protection, increases the brand value and protects against counterfeiting of the end products by making it completely holographic.