Specifications

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the PC cards with their varying thickness, the Type I can fit into all Type II slots, but not vice versa.
Although these cards were dubbed “compact” when they were introduced, today they are the
largest of the cards most commonly used. Many people expected the CF cards to lose in
popularity to newer, smaller cards introduced since 1994; but their larger physical layout has
actually worked in their favor, particularly for digital cameras that have grown in both sophistication
and in their requirements for larger storage capacity. The larger physical dimensions of the Type II
Compact Flash cards allow their capacities to reach 16GB, three and half times more than a DVD!
The increased capacity is handy because digital cameras have moved from the resolution provided
by one million pixels (1 megapixel resolution) to that of 10 megapixels in the most advanced
cameras as their picture resolution exceeds the theoretical “film quality” of 7-8 megapixels. A
Minolta Dimage 7, a 5-megapixel camera, can hold 22 “economy” quality pictures on a 16MB
Compact Flash card at its highest 2560x1920 image resolution setting, but only 1 “Super Fine”
picture at that resolution. A standard SLR film camera, on the other hand, will take 24 “film quality”
pictures on a typical role of 35-mm. film. The Minolta Dimage 7 would need a 128MB Compact
Flash card to hold 7 or 8 Super Fine pictures at its highest resolution (2560x1920), but the same
card could hold almost 60 “Fine” pictures and over 170 economy photos. Figure 7 is a chart of the
differences between typical cameras’ flash card capacities for two different quality settings
producing medium sized pictures at a resolution of 1,024x768. As the numbers in the chart show,
the more advanced the camera, the more storage capacity it needs.
Number of Images per Flash Card
File size of 1 image
4
Camera
superfine/economy
8 MB
16MB
32MB
64MB
128MB
256MB
1 megapixel
340/120 kB
22/48
45/120
91/230
182/460
365/950
731/1920
2 megapixel
450/155 kB
16/46
32/92
67/184
135/368
271/732
542/1464
3 megapixel
591/174 kB
12/41
25/84
51/171
103/342
207/684
415/1370
4 megapixel
1002/278 kB
7/26
14/52
30/108
61/217
123/435
242/864
5 megapixel
1600/340 kB
4/22
9/46
20/96
40/188
80/376
160/752
6 megapixel
2100/450 kB
3/17
6/35
12/71
25/142
51/284
102/568
JPEG (Joint Photographic Experts Group) is a file format with several different levels of compression that
range from fine (1:4) to normal (1:8) to basic (1:16). These levels are commonly expressed as quality
ranges of “economy, normal, fine, or even superfine.” Compressing the picture information allows more
images to be stored because the files are smaller. Some digital cameras also allow uncompressed images
in a TIFF format (Tagged Image File Format) that end up being very large files. Compression artifacts are
generally not noticeable unless pictures are enlarged dramatically; but resolution is also a factor in
enlargements, and that resolution depends both on the number of recording pixels built into the camera and
the selected size of the image. Smaller images on the order of 640x480 pixels of resolution will show few
artifacts. Larger images of 1600x1200 or 2560x1920 will tend to show more artifacts unless the camera has
enough pixels to better resolve the images. For decent picture quality, a 1.3-megapixel camera can
reproduce a maximum of 5-inch by 7-inch prints. For 8x10-inch pictures, a camera should have at least 2
megapixels. As the chart shows, cameras with a greater number of pixels create larger files and need more
storage capacity.
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The file size is based on medium sized (1,024x768) pictures in normal JPEG compression. Larger
reproductions requiring greater resolution will yield fewer images; smaller reproductions will yield more. The
actual file size depends on the camera, the selected size of the image, the amount of compression, the
quality level selected, and even the complexity of the scene. All of these values are approximate.
Figure 7