Technology of digital photography

Technology of digital photography

In digital photography each image is, in fact, a file containing an array of data in the digital format. Besides, digital photography uses an electronic device, a sensor, as a photosensitive material.

Both in film and digital cameras, the light from the scene being photographed focuses in a lens, then falls on a photosensitive material (a film or a sensor, in the case of a digital camera).

  a – Scene, b – Lense, c – Film or sensor 

Digital technology in photography made it far easier to take and store photos. Digital photography has many advantages over film, which include:

• Instant review of pictures.
• Greater flexibility and speed in taking photos and getting the result.
• Ability to take and store an almost endless number of images.
• Cheaper permanent storage on digital media.
• Easier and cheaper copying, printing and distributing.
• Ability to embed metadata within the image file, such as the time and date of the photograph, model of the camera, shutter speed, flash use, and other similar items.
• Ability to capture and store hundreds of photographs on the same media device within the digital camera.
• Ability to retouch the photo and apply various filters.

A more comprehensive review of digital photography can be found in this article: "Digital versus film photography"

How digital camera registers the picture

The heart of a digital camera is an image sensor that consists of an array of tiny pixels (PIcture ELements). The number of megapixels (1 Megapixel = 1 million pixels) is one of the major factors for a digital camera, though there are other critical things, such as processing system inside the camera that turns the data from sensors into a color-balanced photograph, the physical size of a sensor and camera lenses characteristics.

 a – IR-Blocking Filter, b – Color Filters, c – Color blind sensors, d – Millions of light sensors 

Sensor pixels are also called photodiodes or sensors. When you press the shutter-release button on your camera, the light starts to fall on photodiodes (elements of a camera sensor), and they begin to store photons into its cavity. Photodiodes are color blind, that is they are unable to determine the color of the light that falls on them. So digital cameras use different color filters to transmit light through. The most common are filters for three basic colors – red, green and blue. So, the camera is able to calculate the number of photons of three basic colors that fell on each photodiode while the shutter was open.
To calculate all color components around each photodiode, red, green and blue filters should be situated adjacently. This makes it possible to convert raw image data into a full-color image in RGB (Red Green Blue) space. The most common type of color filter array is called a "Bayer array".
You can learn more about color filters, and the way they are arranged in sensors, from this article: "Color filter array".

Digital photo size and resolution

When making a photo, you can select resulting photo resolution (number of megapixels in a photo). Maximum resolution is a significant factor for cameras, but it is not the only measure of image quality; a larger sensor with the same number of pixels will generally produce a better image than a smaller one. One of the most important differences is an improvement in image noise. This is one of the advantages of digital SLR (single-lens reflex) cameras, which have larger sensors than simpler cameras of the same resolution. Common image sizes are 640 x 480, 1280 x 960, 1600 x 1200, 2048 x 1536, 3008 x 1960, 3088 x 2056 and 4064 x 2704. The larger image size, the better is printed photo quality.

 

 

 Color reproduction and color spaces

Color reproduction (gamut) is dependent on the type and quality of sensor used and the quality of the optical system. Different sensors have different color sensitivity; the photographer needs to understand his equipment, the light conditions, and the media used to ensure accurate color reproduction. Many digital cameras offer RAW format (sensor data) which makes it possible to choose color space in the development stage regardless of camera settings; in effect the scene itself is stored as far as the sensor allows, and can to some extent be "rephotographed" with different color balance, exposure, etc.

Output image formats

RAW
The uncompressed and unprocessed image data captured from the image sensor is called RAW format. Ordinary, if you are not a professional photographer, you don’t use RAW files, because most part of point-and-shoot digital cameras don’t output photos in this format; besides, you need special RAW converters to process “negative” RAW files into a "positive" file format. On top of that, there is a different RAW format for each manufacturer and camera model. Different manufacturers use their own proprietary RAW formats, and offer their own software for raw processing. Image formats most frequent in the internet are .JPEG, .PNG and .GIF formats.
JPEG
JPEG is a standardised image compression mechanism. This format is designed for compressing either full-color (24 bit) or grey-scale digital images of "natural" (real-world) scenes.
It works well on photographs, naturalistic artwork, and similar material. However, it is not advised to use it for lettering, simple cartoons, or black-and-white line drawings, as files will come out very large or artifacts will be noticeable.
GIF
GIF is an 8 bit format which means the maximum number of colors supported by the format is 256. GIF uses LZW compression algorithm.
GIF format was developed in 1987 by CompuServe to provide a color image format for their file downloading areas. In 1989 the format was enhanced; the new version added support for animation delays and transparent background colors. GIF favors flat areas of uniform color with well defined edges, that is why it is best suited for logos, other sharp-edged line art with a limited number of colors and simple animations.
PNG
PNG (pronounced Ping) is a bitmap graphic format that uses lossless compression. This format was developed to surpass the limitations of GIFs. PNG is patent-free, it has better compression and supports millions of colors. It also provides greater depth of color, catering to images up to 24 bit in color.
However, PNG format will never completely replace GIF, as it doesn't support animation and the difference in compression rate for small images is no more than 5%.

Improvement and retouch of digital photos

Each digital image is, in fact, a set of pixels. In RGB color space each pixel has 3 components corresponding to the three basic colors: Red, Green and Blue. The depth of color (a number of bits used to represent a color) determines how many different colors an image may have.

 

 Example of picture decomposition into 3 color channels: Red, Green and Blue

 

As any image file is a set of digital components, it can be easily edited just by changing the value of Red, Green and Blue components. This is a main principle of any photo editor, either online or offline.
Digital photography has taken photographing into a realm of infinite possibilities when it comes to image editing, storing and sharing. That is why digital photography is rapidly replacing traditional film-based photography.
But even digital photos sometimes are not ideal. A common nuisance is the notorious 'red-eye' caused by the flash light bouncing directly back from the center of the eye. If you use an entry-level point-and-shoot camera, or use a professional camera with improper settings, you may be disappointed with poor color and lighting.
We always want to see well-balanced photos with nice composition, vivid colors and unblemished faces. Of course, you can study Photoshop or ask professionals to retouch your photos, but it takes much time and money. A wise alternative is using online services and easy-to use software tools at Pho.to site that was specially designed to let you fix the most common problems of your photos in a snap.
Pho.to site offers efficient, easy to use and mostly automatic image editing tools (both online and offline). Also, here you will find a wide set of photo manipulation tools for fun and entertainment, like services for making photo montages, creating animated avatars or even changing face mimics on a photo.
 

More useful information on common problems of point and shoot photography and on how to fix them can be found on Photo Tips & Tricks page. There you will also find tips on arranging your photos into cool web galleries and 3D albums.
Pho.to team believe that you will have lots of fun learning to understand and edit digital photography. Don’t be afraid to experiment, you will certainly enjoy it!