Digital Camera Primer
Jan 21 '01
The Bottom Line Don't get carried away with cool-tech. Buy for today!
You can purchase a digital camera for $35 or $10,000 and every price in between. You can get a fuzzy likeness of your new baby and send it to relatives or a real quality photo. What’s the difference? Read on.
What are you going to use the camera for? If it’s a photo for the shoes that you’re selling on e-bay get a low pixel rating (640 by 480) and save some money. The picture will be nicely viewable and download fairly quickly. If your application demands 35mm or higher resolution go the megapixel route but be aware that downloads of your picture will be lengthy.
What’s a pixel or a megapixel? A pixel is a “picture element” or a single point in a graphic image. On a color monitor each pixel is actually three tiny dots: red, blue and green. The more pixels, the better the resolution on your screen (or camera). (Look at a magazine photo or a newspaper’ photo under a magnifying glass. The tiny dots there are analogous to picture elements).
Standard VGA resolution (640 by 480) equates to 307,200 (simple multiplication of the vertical and horizontal) pixels or .3 megapixels. It is the lowest common denominator for most photos. With each pixel represented by 8 bits, you have a maximum of 256 colors available (2 to the 8th power). Higher resolution can get you up to 15, 24 or 32 bits per pixel.
Now lets look at camera specifications. Let’s say we have a camera with 1600 by 1200 resolution. That’s 1.9 megapixels. Multiply this number by 24 to estimate the number of bits in a photo. Divide that number by the speed of your modem (or connection) in bits/second. This gives you an approximation of the number of seconds it will take to send or receive that picture. Now inflate that number by 20 or 30 percent, as your connection will never be 100% efficient.
Most photo’ package’ software can convert your pictures into one of several formats. Bit mapped is full resolution and a real pig in terms of the number of bits. GIF (Graphics Interchange Format) will compress the number of bits to about half while JPEG or JPG (Joint Photographic Experts Group) divides the bit-mapped number by a factor in the area of seventeen. As an example let’s say we have a typical photo that in bit-mapped form contains 500,000 bits. In GIF it will be 250,000 (unless fewer than 256 colors. See above) and JPG about 30,000. To most of our eyes all three will look (about) the same. In terms of download time there will be a dramatic difference.
Now let’s consider printing. For estimation purposes we’ll say that you have a 600-dot/inch printer and a 1600 by 1200 camera. Divide each of the camera’ numbers by 600 and you can get a 2.66” by 2” copy with “best” resolution. Anything larger is going to start getting grainy.
Another important consideration is going to be how the camera communicates with your computer. If your machine has a USB port (connector) and the camera utilizes that technique, it’s pretty simple to “mate” them”. An older computer won’t have a USB but may have a spare serial port: select that interface.
If you have a laptop or palmtop you might think about a camera with a flash card. The flash card is a small (approximately 1”X1”) storage device that can be transferred from camera to computer. There are essentially two types: CompactFlash and SmartMedia. They are not compatible! Sony and a few other vendors offer MemoryStick storage and floppy disk.
The disk option is wonderfully convenient but can be expected to deplete batteries quickly.
Focusing a digital camera that has an LCD viewer will be perfect resolution. If you are using a traditional viewfinder camera the phenomenon of parallax (the camera is looking at a different view then you are) can take a bit of learning. SLR’s are also available.
Higher end digitals have both optical and digital zoom. The magnification can be truly impressive at graduations and sporting events.
For most of us the $200-$500 camera will serve well. I’m however very pleased with my ancient, tiny Mitsubishi (about $40 on places like e-bay) and Polaroid 640. Don’t “overbuy”.
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Member: Steve Howard
Location: Lebanon, Maine
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