Capturing Digital Images

Say Good-bye to 35mm Film Cameras

The days of 35 mm film photography for the consumer and amateur photographers are just about over.

• In January of 2006, Nikon announced it would end production of all but two of its film cameras and accessories and concentrate on digital models. Digital cameras accounted for 75 percent of Nikon's sales as of March 2005.

• In 2005, Kodak announced that they will only make 35 mm film cameras for their high end professional line and for their low end consumer disposable lines.  All the cameras in between these models will be digital.

• Canon has also made a similar announcement saying Good-Bye to 35mm film cameras.

• Europe's biggest film maker, Germany's AgfaPhoto GmbH, couldn't adapt to the digital revolution and is now bankrupt and liquidated.

If you are a professional who has the skill to work with large format films to get high quality landscapes, portraits and reproductions, film still beats digital, but for the rest of the ordinary people in this world, digital will win us over because of it's ability to capture very good color, it's great convenience, and the ease of editing and storing photos on your computer.

Some hard-core fans of film say that film cameras produce quality and depth that cannot be captured by digital, but many photographers consider new high-end digital SLRs to have equal, if not better, quality compared to most 35-millimeter film cameras.

If you want to set up a Website, digital photos are the way to go.  No film to buy or be developed, no negatives to mess with, no paper photos to scan, no time spent delivering and picking up film and prints.  Just grab your digital camera, shoot your pictures, load them onto your computer's hard drive and add them to your Website. 

Even if you need to do a little editing on your pictures before putting them on your site, there are numerous, low cost photo editing programs (discussed below) available that make the task so simple, that even the most "Photographically Challenged" individuals can do it with a few clicks of the mouse. 

Some cameras even have LCD viewers that allow you to see the picture immediately after you take the picture so you can see if it's what you want.

How A Digital Image is Captured

Digital cameras are very similar to the traditional film cameras.  The big difference between them is how they capture an image.

Film cameras record the image on film that is coated with chemicals that sense color and the intensity of the color.
Digital cameras use an electronic chip called an Image Sensor

There are two types of Image Sensors:
CCD or Charge-Couple Device and CMOS or Complementary Metal-Oxide Semiconductor.

CCD is the most common.  They generally give better image quality and have a greater dynamic range.  They also offer faster speeds.  However, CCDs tend to be more expensive and use more power.

CMOS sensors are larger than CCDs, often resulting in bulkier cameras.  CMOS sensors are getting better and some are better than CCDs.

The surface of the Image Sensor chip contains a grid of hundreds of thousands or millions of Photosensitive Diodes or Photo elements, also known as Pixels (Picture Elements).  Each pixel in the Image Sensor will capture the intensity of the light for each pixel in the photograph.

When the shutter of a digital camera opens, each pixel on the image sensor records the brightness of the light that falls on it with an electrical charge. The more light that on a pixel, the higher the charge, the less light, the smaller the charge.

The charge from each pixel is then converted to a digital number and that number is used to set the color and brightness of the pixels which you will eventually see on your computer monitor or printer.

Each pixel on the Image Sensor can only capture the brightness or intensity of the light, not the color. They record a gray scale brightness that is any one of 256 different levels of gray ranging from 100% white to 100% black.
(Picture by Fuji - text has been added for clarification.)

To get a color photograph, each pixel is covered with either a Red, Green or Blue filter, so then each pixel is actually recording the brightness of the light for the color of the filter that covers it.  Only Red light can pass through a Red filter, so a pixel covered with a Red filter is only recording the brightness of the Red light, all the other colors are blocked out by the Red filter.  As shown in the picture, there are more Green filters than Red or Blue filters.  That is because the human eye is more sensitive to green light, so there are more Green filters to increase the accuracy of Green colors.

On top of the color filters are lenses that help collect the light and make each pixel or individual sensor more sensitive.

All of this information has to be processed and recorded and there are other calculations that take place during this brief time span when you click the shutter.  For each picture, there are millions of calculations that have to be made in just seconds.  All of these calculations are performed by a microprocessor chip in the camera, similar to the chip that's in your computer.  This chip makes it possible for the camera to preview the picture, record it, compress it, store it, transfer, and also display the image on the LCD viewer.

RGB Color

You've probably heard of a computer monitor being referred to as an "RGB" display.  This is because the images it displays are formed from light that is projected from multiple pixels, each one having one of the three Primary Colors, either RED, GREEN or BLUE.  By combining different amounts of each of these colors, a monitor can display up to 16.7 million different colors.  This color system is called the Additive Color System because when these three colors are combined (added together) in equal amounts they form white. When Red and Green overlap, the form Yellow, when Red and Blue overlap they form Magenta, and when Green and Blue overlap they form Cyan.

This RGB color system occurs whenever light is projected to form colors.  Colors in a photographic image are based on the Primary Colors and so is natural daylight.  This is why a color image can be produced by simply placing red, green, and blue filters over individual Pixels on an Image Sensor in a digital camera.

To read more about color see my section on Color Systems.

In the next section, Common Digital File Types, I'll discuss the different file types that Digital Cameras use to store their Captured Images and how this is relates to Image Resolution, both Optical and Interpolated Resolutions.

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