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IMT – Cholla Training Center
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Pixel Count
One of the main ways that manufacturers categorize their digital cameras is in terms
of pixel count. This is the number of individual pixels that go into making each image.
Today this number varies between 1 million (1 Megapixel) to around 14 million (14
Megapixels). A million pixels is abbreviated to MP, so a 1MP camera has 1 million
pixels and a 3MP camera has 3 million pixels. Currently most popular consumer
digital cameras have between 2MP and 5MP. A 3MP camera can make excellent 4”x6”
prints and very good 5”x7” prints. If you intend to make lots of 8”x10” prints, then
perhaps a 4MP or 5MP camera would be a better choice. Sometimes two numbers are
given, total pixels and effective pixels. Total pixels count every pixel on the sensor
surface. Usually the very edge pixels aren’t used in the final image. Effective pixels
are the number of pixels actually used in the image after the edge pixels have been
dropped.
3MP 4MP 5MP
Largest Image
(typical) 2048 x 1536 2272 x 1712 2592 x 1944
Print size at 320dpi 6.5” x 4.8” 7.1” x 5.4” 8.1” x 6.1”
Print size at 240dpi 8.5” x 6.4” 9.5” x 7.1” 10.8” x 8.1”
Storage of Images on a Digital Camera
A digital camera stores the pictures it takes on a memory card. Common cards found
in current digital cameras are SmartMedia, Compact Flash and Memory Stick. (Note:
The Sony Mavica stores pictures on a floppy disk.)
A memory card is measured by its memory size, in megabytes (MB). The more
memory the card has the more images it can hold. Thus, a 256 MB memory card will
be able to hold many more images than a 32 MB memory card.
3MP 4MP 5MP 6MP
128MB Memory 116 87 70 58
256MB Memory 232 174 140 116
512MB Memory 464 348 280 232
The number of images placed on a card can vary based on the following factors:
• Compression
• Resolution
• Photographic Conditions
Compression
When a digital camera takes a picture, a very large file is created that holds the
image. A picture produced from a 2-megapixel camera will produce a file size around
6MB. To fit more images on a memory card, digital cameras compress these image
files. The amount of compression a digital camera does to an image can usually be
set by the user. Standard compression modes on digital cameras usually include
either:
Good, Better, Best or…
Normal, Fine, Superfine
The default on most digital cameras will be either “better” or “fine”. While the amount
of compression a camera does will vary from camera to camera, generally a