Describing the role of the pentaprism in the DSLR mentioned a total internal reflection of light. We explain this phenomenon accessibly as possible. Let shown here is a cross sectional drawing of an aquarium filled with water. From the bottom of the aquariumthrow a beam of light toward the surface. The direction of the beam determines the angle between the normal (perpendicular) to the water surface and the radius. This angle is called the angle of incidence at the border facilities (water and air).

For small angles of incidence, such as the angle marked in blue, light comes out of thewater and continues through the air.
For a certain angle, called for the border (marked in red), the beam will not go out of the water and "slides" over the surface,
For angles of incidence greater than the critical angle the light reflected from the surface of the water and returns to it. Reflection is completely lossless, ie there is no loss of energy. Hence the name of total internal reflection

This phenomenon occurs whenever the light goes from the center of the denser (with higher refractive index) to the rarer and therefore such

- from water to air

- glass into the air

The phenomenon of internal reflection całkowitegoo is the basis for the construction of fiber optics. In a thin rod of glass or transparent plastic light can travel without any loss of energy very long distance, bouncing off the walls in succession from the bar.

In each SLR, a camera with interchangeable lenses and a mirror directing light rays to the optical viewfinder, there is a pentagonal prism. The prism is used to direct light raysreflected from the mirror to the eye of the photographer. Schematic of light rays in theSLR, is shown in the accompanying drawings.

Structure and elements of an SLR

The SLR camera with a specific structure, so it will devote a separate chapter. Canon has released a document describing very precisely DSLR EOS-1D Mark IV. This is a pdf document larger than 7 MB, so when the first download should be saved to disk for looking into it does not require multiple downloads from the network. This is called the white paper, this term means an official document that explains very accurately describing a problem or a product. In other words, this is a very accurate description of the parameters and rules of operation of the camera. The document has 123 pages and contains many photos, diagrams and charts explaining the operation of the different elements of this camera. Since the Canon EOS-1D Mark IV is currently one of the most advanced models of digital photography apartów SLR class, we use the information contained in this "White Paper" for explanations of the workings of many elements of this type of camera. The best solution is studying the original document, but it is in English and not everyone can handle and understand some subtleties of language. We will not explain it dokmentu, because you must have permission from the copyright holder and only on the basis of the principles we describe the basic elements of an advanced SLR, popularly called as cameras with interchangeable lenses and a movable mirror directing the image from the lens to the viewfinder. Studying the various paragraphs of this chapter should have opened the original document that you can quickly look at the drawing, or diagram illustrating the described problem.