Copyright Michael Karbo, Denmark, Europe.


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    Chapter 4. Images: from light to RAM

    The photographic process consists of catching a light impression in a camera. The image has to be fixed so that it can in one way or another be conserved for the future. This is done with image sensors, image computers and RAM.

    In old-fashioned analog cameras the light was caught onto a chemical film, which reacted to the energy of the light. When the film was developed, the image was fixed on to the film’s surface. It’s not done at all like this in a digital camera.

    From the outside the exposures in the two types of cameras look just like each other. We are talking about rather short exposure times (e.g.1/200 second), when the light’s rays are focused in the lens and gathered in the camera. But all the similarities stop here. In a digital camera the light is not caught on a piece of film but by a light sensitive sensor, which converts the energy of the light into an electrical form.

    Figur 11. If we try to make a comparison with an analog camera, it is the image sensor (1), which gathers the light. The fixation of the exposure itself takes place in the camera’s image computer (2) with the help of advanced electronics and software and the image is finally stored in the memory card (3).

    The image sensor

    An image sensor is an electronic chip, which is installed on a print sheet inside the camera. Its surface is covered with millions of small “eyes” (pixels), each and every one of them registering a certain amount of light. With the help of advanced electronics these millions of light information are converted into digital images. Here is a 6 megapixel sensor, ”the film” in the digital camera:

    Data from every single exposure is processed in the camera’s image computer where they are converted to image files. The files are finally stored in the memory card.

    The image files are digital. This means that they can be copied and transferred time and time again, as many times as you want to, with losing their quality. We will be looking at this later on in the book.

    Figur 12. You can see here the inside of a Nikon Coolpix-camera. The image sensor is installed on a print sheet with the lens placed over it. The image’s data is sent from the sensor to the image computer, which is a little chip on the print sheet. It is the task of the image computer to store photographs in the memory card.

    As a memory card has a limited capacity, it has to be emptied now and again. This is done by transferring the image files from the memory card to the computer’s hard disk either by using a cable between the camera and a computer or by putting the memory card in a little card reader, which is connected to a computer.

    This picture shows a so-called xD card, which is the smallest on the market. It doesn’t use very much power and is especially good for very compact cameras with limited room. These small cards can be a little difficult to get out of the camera, so it is easiest to transfer the images to a computer through a USB cable.

    A USB-based card reader, which is used to transfer image files from a camera’s memory card to a computer. You can also make a direct connection between a computer and the camera but a cable will have to be used every time:

    The card reader doesn’t take much room on a desk and the only thing you have to do is to slide the memory card into it. A card reader works like a drive in Windows, e.g. an E-drive. This means that you can use Windows Explorer to transfer the files from the memory card to the image archive on the hard disk.

    Figur 13. There are three sockets on the side of this camera, which can be used for USB (computer connection), video (television connection) and power supply. A small soft plastic door covers the sockets. The USB socket transfers images from the camera to a computer, without having to move the RAM-card. This is especially smart, when a memory card is small and difficult to handle.


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