Digital Photography
Created by Joel May November, 2007
revised January, 2009

Part I - Features of a Digital Camera

  1. Resolution
    2.

    1. Resolution is determined by the sensitivity of the CCD (charge coupled device) or CMOS (complementary metal oxide semiconductor) in your camera]
    2. This, in turn, is determined by
      1. The number of photo-sensitive cells (photo diodes) on the device (measured in pixels)
      2. The sensitivity of each of the cells (measured in bit depth or dynamic range)
      3. The physical size of the cells
    3. In all three cases, higher is better in terms of image quality
      4. Today, a 6-megapixel CCD is pretty much the minimum you should buy

  2. Compression

    1. Digital cameras are capable of compressing images to create smaller file sizes
    2. They do this with minimal quality loss
    3. Every digital image is a bitmap (BMP) or matrix of adjacent pixels.
      1. If you would enlarge a small area of a bit-mapped image you would clearly be able to see the pixels of which it is made
      2. Together these pixels form a massive grid that creates the illusion of a continuous tone image
      3. The number of pixels in this matrix determines the size at which such an image can be printed or displayed

  3. Formats
    1. Some digicams let you save the raw image data straight from the CCD in an uncompressed file format called CCD RAW
      1. This format contains all the information as captured by the CCD as no in-camera processing is performed
      2. It can be transferred to a computer where the data can be worked on to produce the final image
    2. The Tagged Image File Format (TIFF) is a very flexible image format which was created to save images created by scanners and image manipulating programs
      1. It produces an excellent quality image
      2. A disadvantage is that it creates very large files. Typically an image from a 3-megapixel camera will take up more than 9Mb of space on your storage card
    3. The JPEG format (Joint Photographic Experts Group) which supports 24-bit color, can be read by many applications because it is a standardized image compression mechanism
      1. Created especially for the transmission and storage of photographic images, it offers a significant reduction in file size
      2. However, it uses a lossy compression scheme by averaging the data in blocks of 8 x 8 pixels. Color variations that existed in the original image are lessened
      3. Although digital images can be compressed at up to 100 JPEG quality levels, most digital cameras that use JPEG let you save the images at three settings, usually marked Fine, Normal or Low, though the exact terms used may vary from one manufacturer to the other
      4. This means that you have a choice as to how much information will be lost during compression and consequently what the final quality of your image will be
      5. But beware, since every time you open and save a JPEG file the image is compressed again so repeatedly saving the same image will seriously degrade it
    4. The EXIF (Exchangeable Image File) format is used by nearly all digital cameras to store extended camera information
      1. It contains information about the time and date that an image was taken, together with exposure information such as ISO-speed, shutter time and aperture used
      2. When an image is compressed by EXIF it stores the information in the header of each JPEG file. This means that any program that supports JPEG files, which includes all web browsers and image editing applications can read the information
    5. As it is not always possible to determine beforehand what an image will be used for, you should, if possible, always use the highest quality setting, since information lost can never be retrieved.

  4. Memory / Storage

    1. Digital cameras do not use film to capture images. Instead pictures are saved on some form of internal storage media or memory cards. Their capacities range from 4Mb to 8GB and are increasing all the time as technology progresses. There is even a 1Gb Microdrive available for use in certain cameras
    2. Memory cards can hold quite a number of images, depending on the chosen resolution and/or the capacity of the card. If you aim to take many high-resolution pictures it pays to buy the largest memory cards you can afford since high-resolution images eat up memory at an alarming rate
    3. There are a number of different memory devices available:
      1. Smart Media Cards. These are the memory cards used most by today’s digicams
      2. Compact Flash Cards
      3. Memory Stick
      4. MultiMediaCard
      5. xD-Picture Card
      6. The IBM Microdrive
      7. and more
    4. How much memory do I need? (examples)
      1. In a standard 16 MB storage device and a 1.3 Megapixel resolution
        1. JPG format (compressed standard) – about 55 pictures
        2. JPG format (compressed fine) – about 35 pictures
        3. JPG format (uncompressed) – about 20 pictures
        4. TIFF format – about 8 pictures
      2. For an 8” X 10” print at 300 dots per inch: (8 x 300) X (10 x 300) = 2400 x 3000 = 7.2 million pixels
        1. A 16 MB memory device will hold about 2 pictures
        2. A 256 MB memory device will hold about 36 pictures
        3. A 1 GB memory device will hold about 139 pictures
      3. For a 4” x 6” print at 300 dots per inch: (4 x 300) X (6 x 300) = 1200 x 1800 = 2.16 million pixels
        1. A 16 MB memory device will hold about 7 pictures
        2. A 256 MB memory device will hold about 118 pictures
        3. A 1 GB memory device will hold about 463 pictures
      4. For a 5” x 7” e-mail or computer screen image at 72 dots per inch: (5 x 72) X (7 x 72) = 360 x 514 = 185,000 pixels
        1. A 16 MB memory device will hold about 86 pictures
        2. A 256 MB memory device will hold about 1,383 pictures
        3. A 1 GB memory device will hold about 5,405 pictures

  5. The Viewfinder

    1. The viewfinder is the window in which you compose the image. There are four varieties: optical, LCD screen, electronic and through the lens
    2. Optical viewfinder
      1. The simplest and most common type in use. It is not very accurate in framing the scene as it doesn’t look straight through the lens and is mostly slightly offset both horizontally ad vertically. It only shows about 80% to 90% of the actual image.
      2. Optical viewfinders suffer from parallax error. As they are not completely in line with the lens, they show a slightly different view than the actual image. This will not be a problem i iages taken from a distance, but when capturing close-ups this is something to take into account.
      3. Nevertheless, they are the easiest to use and the least expensive.
    3. LCD screen
      1. Featured on almost every digicam nowadays. It lets you review images, change camera settings or frame the scene
      2. The LCD screen eliminates the parallax error problem inherent in the use of the optical viewfinder
      3. Since it is much more accurate than optical viewfinders, many users compose the image through the LCD screen.
      4. However, they drain batteries fairly quickly and they may be difficult to judge in bright sunlight.
    4. Electronic viewfinder
      1. An electronic viewfinder shows the image on a very small LCD screen.
      2. It is used in the same way as the optical viewfinder but is much more accurate since it doesn’t suffer from parallax error.
      3. The are a major cause of battery drain
      4. The view is quite coarse, which makes it impossible to check finer details in an image such as whether someone’s eyes are open or partially closed.
      5. They tend to show an overly bright view, which makes it hard to judge correct exposure of the scene.
    5. Through The Lens (TTL) optical viewfinders
      1. Usually found only found on high-end digital SLR (single lense reflex) cameras because of its complexity and cost.
      2. The most accurate system of all since you can look at the scene straight through the lens through a prism or mirror system.
      3. While no system is perfect, optical TTL viewfinders are best in most situations, since they don’t suffer from parallax, don’t use battery power and clearly show all the details in a scene.

  6. Flash

    1. Sometimes the available light is not enough to create the image you are after, and some form of artificial light is needed.
    2. The most readily available is your in-camera flash.
      1. To make full use of the available flash power, always wait for the flash-ready light to be lit before pressing the shutter.
      2. It is rather limited in its coverage as its power is usually only enough to cover subjects of about three to four meters (15 to 25 feet) away
      3. It can be a very useful tool as a fill-in flash to supplement available light and to lighten up dark shadows in your subject.
      4. In-camera flashlights invariably cause red-eye when photographing a person looking straight at the camera, because the beam of light is too close to the axis of the lens. Using a of-camera flashgun or making sure the subject is looking away from the camera, will avoid this.
      5. Using flashlight at concerts or stage shows in large halls or stadiums is useless. Try getting closer to the stage or failing this, support your camera firmly and use a slow shutter seed.
    3. Flash Modes - Many digital cameras have a variety of flash modes. They usually include:
      1. Flash on - the camera fires the flash whenever the exposure system decides it is necessary. The light is quite harsh, making the subject stand out against a dark bckground.
      2. Forced on - the flash always fires when you press the shutter, regardless of the amount of available light present
      3. Flash off - turns the flash off so you can capture an image with available light without the flash firing.
      4. Anti red-eye - used to reduce red-eye when taking a picture of a person looking straight at the camera. A pre-flash makes the eye’s pupil contract and lessens the red-eye effect. I is not very effective though.
      5. Slow synch or fill-in mode - the most versatile. The camera will choose a shutter speed for the ambient light plus a small dose of flash to lighten the foreground. This will make for balanced picture as the subject will be lit by the flash while the background will be recorded as well. Fill-in is also very effective at lightening up dark shadows in harsh sunlight. This feature is uually available only in top-of-the-line cameras

  7. Time Delays

    1. Start-up Time
        2. After turning on your digital camera, it takes some time before it is ready to use.
      1. Start-up time with digicams is usually between 2 to 5 seconds, which is considerably longer than with conventional compact cameras.
      2. The reason for this is that the built-in processor will have to do a “self-test” to determine all the settings, load the operating system (just like a PC) and get everything ready for capturing an image.
      3. To shorten start-up time, off the flash before turning off the camera. The reason for this is that if the camera is set to automatic mode, you additionally have to wait for the flash capacitor to charge, before you will get a ready signal. This can mean a further couple of seconds before you can take a picture. Switching off the flash when turning the camera off also means that you save on batteries, since this is one thing digital cameras consume at an alarming rate.
      4. Because of this time lag at start-up, your camera must be switched on beforehand if you want to take candid or action shots, so you will be prepared for anything that might be worth capturing on camera.
    2. Shutter Lag
      1. Digital cameras need some time before they are ready to capture an image.
      2. After pressing the shutter release button it will take some time before the actual picture is being taken.
      3. This phenomenon is called shutter lag and it can be more than a full second on some cameras.
      4. This delay is caused by the time it takes the camera to adjust white balance, focus on the subject and calculate the exposure settings
      5. This time lag can be the cause of missed photo opportunities because not every subject is static enough or willing to wait for the camera to be ready.
      6. To deal with this, in anticipation of the action taking place before you
        1. Press the shutter button halfway to lock focus and then wait for the decisive moment to release the shutter.
        2. Use burst mode on your digicam, capture several images after another and select the best one afterwards.

  8. Batteries

    1. Digital cameras need a lot of electrical power to perform their multiple functions. Your best choice would be to use rechargeables.
    2. There are several types of batteries
      1. Disposable type AA Alkaline
        1. Low power, short life, inexpensive.
        2. Should be removed from your camera when not in use to avoid corrosive chemical leaks
      2. Disposable type AA Lithium
        1. Relatively powerful, hold their power for years, relatively expensive
      3. Rechargeable type NiCd (Nickel Cadmium)
        1. Moderately powerful, relatively short shelf life, relatively inexpensive
        2. Can be safely left in the camera for prolonged periods, gradually lose charge if not in use
        3. The have “memory” problems. If they are not fully discharged before being recharged, they will fail to recharge completely
      4. Rechargeable type NiMH (Nickel Metal Hydride)
        1. Moderately powerful, longer shelf life, relatively inexpensive
        2. Can be safely left in the camera for prolonged periods, gradually lose charge in not in use.
      5. Rechargeable Lithium Ion batteries
        1. Three times as powerful as NiCd or NiMH
        2. Possess excellent cold weather performance and have a shelf life of up to 10 years
        3. Can be recharged many times, relatively expensive
        4. Can be safely left in the camera for prolonged periods, hold their power for years
        5. Have been known to explode in laptops and cell phones