Photograph
Astronomer John Hershel in Britain invented the word "Photograph". The opinion that it was a meaning "One thus (It writes, and draw)" and "..being able to start.. one .."photo-".." .."Light" and "-graph".., and it was possible to translate into "Picture of light" by matching it is necessarily incontrovertible. However, it was invented ..light.. ..copy.. to mean it in Japan, that is, "The spectacle is copied". It might be called the photo from "Photograph" for short. The photograph is called an image in case of electronic data of the digital photography.
Principle of photograph
Optical operations of refraction and the interception, etc. are done to light with equipment such as lenses and cameras, it irradiates to the material (exposure material) exposed to the light of specific wavelength, and it is exposed. Light and shade is reversed and a final image is obtained by expanding if necessary for a exposed exposure material by the operation of the disappearance of the exposure abilities such as making to visible about development etc. and established etc. , the printing, and the print, etc.As for the obtained image, the thing that applies light again and appreciates is possible.
Principle of silver halide photography
When halogenation silver gives light, silver that the silver ion is reduced, and not ionized can be done. It doesn't become an image as it is even if exposing and becoming silvery. Silver in the exposed part should increase the number of silvers up to a suitable amount for a very small amount. This is done with the developer. Moreover, because a part not exposed is embarrassed when it is exposed any more, it is necessary to remove the silver molecule in an unnecessary part. This is done by the established processing.
The area where wavelength is absorbed depends on blue when halogenation silver is exposed. Then, it is set that the reaction takes place besides original absorption wave length by using the photosensitizing dye to extend to the visible region and to expose it. First of all, because the photosensitizing dye responds to light, and the electron of the coloring matter moves to halogenation silver, the change similar to the exposure directly of halogenation silver is approved. If it exposes only to a specific wavelength area of a visible electromagnetic radiation, and the photosensitive layer piled up to correspond to three primary colors, it becomes a color film.
Principle of semiconductor image sensor
When the photon that enters into the semiconductor image sensor enters the pn junction for CCD, the electron is generated. The quantum efficiency is high sensitivity because it is far higher for halogenation silver of the silver halide photography. It sends it to analog-to-digital converter by scanning the generated electron. Strength of the signal is recorded in the recording medium for VHS etc. analog according to the quantity of electric charge. (Shannon = Hartley's theorem)
Strength of potential is recorded in the recording medium by potential's changing for the vidicon tube with the photon that enters into the photoelectron surface, and scanning.
Principle of semiconductor image sensor
When the photon that enters into the semiconductor image sensor enters the pn junction for CCD, the electron is generated. The quantum efficiency is high sensitivity because it is far higher for halogenation silver of the silver halide photography. It sends it to analog-to-digital converter by scanning the generated electron. Strength of the signal is recorded in the recording medium for VHS etc. analog according to the quantity of electric charge. (Shannon = Hartley's theorem)
Aspect foul and reciprocity failure
The amount of the exposure in the photograph is basically decided depending on the amount of light (time that amount ~ light of light each unit time is hit). This is called an aspect foul. However, the amount of the exposure is not proportional to the amount of the entering light even where either. It doesn't thicken any more even if light more than constancy is applied because halogenation silver that doesn't become a light color, and is exposed more than the base film is limited as for the unexposure part. Therefore, when an incident amount of light and the density of the image are made a graph, it becomes like the sigmoidal function. The middle part of change straight line, and the inclination of this part is called a gamma.
When the exposure time extremely is short or long, the aspect foul might not be approved. This is called a reciprocity failure. It gives birth to another further problem in the color film. The color balance collapses because the state of the reciprocity failure is different in each color. Yet another problem is in the exposure for a long time. The random noise generated from a thermal noise and defective production in the image gets on in the digital camera that can be used now. The function to reduce the noise when exposing it for a long time in a part of digital camera has adhered. It is necessary to operate the detector at the low temperature so as not to influence an image final the noise when exposing it at very long time. However, the grainy doesn't change for a long time in the exposure in the film.
Source where it is known to be able to decrease reciprocity failure when exposing it for a long time by cooling experiencing necessary. When astrophotography is taken, the reciprocity failure becomes a big problem. The film for the heavenly body taking a picture that adjusted no aspect foul [**] measures and the spectrum sensitivity when exposing it for a long time was marketed in around 1977.
Taking of photograph
The camera and camera [obusukura] are the movie camera machines. Other methods might be adopted though the photograph film or the electronic record card is a recording medium. For instance, because the movement of not the photograph film but static electricity is used, it is said an electronic copy (electrostatic copy) though an optical copy and a dry copy (0 copies) make the image that can be used for the long term. The photogram such as [reiyogurafu] that Man Ray published is an image that can be done by the shadow projected to printing paper, and with a camera. It is also possible to copy the electron by putting the taking a picture object directly on the glass side of the scanner.
To expose the recording medium to necessary amount of light, the photographer can select and operate the camera and the lens (The photograph film or the solid state image sensor is usually used as a recording medium).
It seems that the object of the selection and the operation includes the following etc.The operation of the camera relates mutually.
Squeezing
F value of the left side is small, and F value of the right side is large.
The gross weight of the light that reaches the film plane changes by stopping down the lens at the exposure time. The exposure changes if either is changed among these. (Even if it is a camera without a physical shutter. )The exposure time is shown at the shutter speed. When the exposure time is shorter than one second, the molecule is usually written by the fraction of one, and it is displayed by the reciprocal at the second when described clearly in the shutter speed setting dial of the camera. This shows the brightness of the lens though squeezing is displayed by F value. F is F of focus ratio (focal ratio). The diameter of squeezing grows by the route twice whenever F value becomes 1/2 route times, and the area of squeezing doubles. This means the amount of light becomes half whenever the figure grows though F value carved for a typical MF lens is 2.8, 4, 5.6, 8, 11, 16, 22, and 32, etc.
Various combinations are approved to the shutter speed and the squeezing value of a specific exposure. For instance, the same amount of power can be gained in 1/125 seconds in F 8 and 1/500 seconds in F 4. Naturally, which combination was chosen influences final finish. The change in the shutter speed changes the degree of the reflection of the movement of the object and the camera (blur). The change in squeezing changes the depth of field.
The depth of field is a range with the focus that extends before and behind the focus seem. For instance, suitable of the focus and not seeing the head of the nose when sharply focusing happen in eyes of the object when squeezing is opened and the long focus lens of the large caliber is used. It is easy to take the photograph that seems to be appropriate for eyes of the object and noses of the focus if it focuses on the distance reversely squeezing with a short focus lens of the small caliber and crowding (The squeezing value is enlarged) and it uses it.
The depth of field becomes extremely shallow if it opens the diaphragm with a long focus lens of the large caliber and it focuses it on the short distance. The depth of field becomes extremely deep if it focuses it on the distance reversely squeezing with a short focus lens of the small caliber and crowding (The squeezing value is enlarged). Even if the position of the squeezing value, the focal length, and the focus is the same, the depth of field is different depending on F value of the lens (F value when squeezing is opened). Moreover, even if F value of the lens is the same, the depth of field is actually different from the design and the mark depending on the difference etc.It is possible to focus the camera by using a very small squeezing like the pinhole within the very wide range. This is called pan-focus.