Digital Cameras

Digital Cameras

And toss out those analog video cameras - digital video cameras offer improved picture quality, sound and the ability to upload video to your PC for editing and inclusion in documents and your web site.  It is time to make the move to digital imaging!

Once you decide to "go digital" for your imaging needs, you'll have lots of choices in lots of price ranges.  And, like any technology, the specifications are filled with both basic camera and digital camera terminology that can be somewhat confusing.  So, before you purchase that hot new camera, we thought a quick review of the some of the key technical terms might help.

• Resolution - Expressed in "megapixels" (MP), is the detail that your camera can capture.  The better the detail, the larger print you can make (you probably know the term 'blow up' - that is what resolution is about).  For digital cameras, an image resolution of 640x480 (0.3 megapixels) results in a good wallet size print, 768x512 (0.4 megapixels) a 4x5" print, 1152x768 pixels (0.8 megapixels) 5x7", 1536x1024 pixels (1.6 megapixels) 8x10".
• Sensor - The image sensors are the devices that convert light into electrons.  There are two main types, CCD (charged coupled device) and CMOS (complementary metal oxide semiconductor).  CCD sensors are more expensive but give great fidelity and light sensitivity.  CMOS sensors are cheaper, have less sensitivity and consume less power.  Because digital cameras are often compared to their 35MM film counterparts, digital camera sensitivity is often rated on the film "ISO" standard for film sensitivity. ISO 100, 200, 300, 400 etc.   The higher the number, the greater the sensitivity.
• Memory - The amount of memory in the camera determines how many images you can store before you have to download them to your PC.  In general, a 640x480 resolution image is around 80Kb, 1632x1232 500Kb and 1632x1232 900KB.  You can see that if you are taking images at higher resolutions, you'll need more memory!
• Lens - The lens is described using a number of terms:
  • F-Number - indicates the size of the lens aperture opening. Standard numbers for calibration are 1.0, 1.4, 2, 2.8, 4, 5.6, 8.11, 16, 22, 32, etc.  Each change results in a doubling or halving of the amount of light transmitted by the lens to the sensor.
  • Focal Length - the distance between the sensor and the optical center of the lens when the lens is focused on infinity.
  • Zoom - the ability to vary the focal length.  Optical zoom changes the focal length of the lens.  Digital zoom magnifies a portion of the data that comes from the sensor (ignoring the rest) and basically adds detail to the "chosen" data coming from the sensor.
  • Aspherical Zoom or Lens - Aspherical lenses (in contrast to standard sphere-shaped lens) are used in ultra-wide angle lenses or large-aperture lenses to correct spherical distortions and aberrations.
• Shutter Speed - The speed at which the shutter opens and closes for the "exposure".  If you are shooting sporting events, a fast shutter speed is essential.

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• Compression - Is very important (remember the memory problem outlined above) in still and video environments where you are not using CDs, MiniDV or other recording media.  For images, TIFF and JPEG formats are used (the compression qualities and algorithms vary by manufacturer - the best quality, the biggest file).  For video and audio, MPEG compression is used with compression capabilities varying from 25:1 to 50:1.
• Frame Rate - The number of frames/images taken a second in video.  Faster frame rates are, again, best for 'action' shots - like sporting events (or checking out your golf swing!).

Done with your quick "term review"?  Great!  Now let's move on to either the Digital Still Cameras or Digital Video Cameras page to not only discover what to look for in YOUR camera, but also the offerings by manufacturer and how we rated them!

If you want complete descriptions of how cameras and digital cameras work, see - How Stuff Works - Cameras or How Stuff Works - Digital Cameras.  For a glossary of photographic terms (very helpful sometimes!) see - Maximum Impact Research - Photography Glossary of Terms.