Digital Photography: Pixels Don't Have to
Be a Puzzle
Contributed by Sheri Graves
“The children were sleeping, all snug in their beds, with visions of megapixels dancing in their heads …”
Technology has changed everything, even the way we take pictures and print photographs. In the world of bits, bytes, pixels and megapixels, clarity depends on an intricate combination of elements.
What we used to leave to professionals, we now struggle to do ourselves in the privacy of our own homes. Success may seem random at first, but a little knowledge goes a long way.
Take the word “pixel.” Please.
“Pixel” is the term used for “picture element,” but with the abbreviation “pix” for picture.
A pixel is an abstract unit of information that appears as a single point in a graphic image. A photograph may appear as a single image, but in fact, it is a collection of pixels, each of which holds different information.
Your kids know this term because they’re adept at using digital cameras and cell phone cameras, sending the photos to their home computers or laptops, and then enlarging the pictures before printing.
At best, pixels in an image can be reproduced in any size without the appearance of visible dots or squares. It takes experience to achieve this look. It also takes an image of fine resolution to begin with, so that the reproduction also will have fine resolution due to a density of “PPI,” or “Pixels Per Inch.”
At worst, the dots or squares are visible. This may be the result of inexperience. More likely, however, the appearance of dots or squares in a reproduced image is the result of poor quality due to fewer “PPI.”
Your kids probably are familiar with the term “PPI.” which stands for “Pixels Per Inch.” Sometimes the measures “dots per inch” (DPI) and pixels per inch (PPI) are used interchangeably. But they have distinct meanings especially in the printer field, where dpi is a measure of the printer's resolution of dot printing (e.g. ink droplet density). For example, a high-quality inkjet image may be printed with 200 PPI on a 720 DPI printer.
In brief, the more pixels used to represent an image, the closer the reproduction will resemble the original.
The intensity of each pixel is variable; in color systems, each pixel has typically three or four dimensions of variability such as red, green and blue, or cyan, magenta, yellow and black.
PPI is a function of the size of the photo as well as the number of pixels the camera’s sensor supports, also known as megapixels. So, to calculate the image’s PPI, these are the steps:
- Measure the image or photograph.
- Multiply the length of the image times the width in inches.
- Divide the number of pixels the camera’s sensor supports by the number of the image’s square inches.
- Find the square root of the result.
Let’s say you have a five-megapixel camera. The following shows the PPI for the page sizes noted:
- 4X6 inches = 456 PPI
- 5X7 inches = 337 PPI
- 8X10 inches = 250 PPI
- 11X14 inches = 180 PPI
- 16X20 inches = 125 PPI
- 20X30 inches = 91 PPI
Since the greatest density of pixels per inch will provide the best resolution, the smallest reproduction (as shown above at 4X6 inches) will result in the best picture. Clarity decreases as the size of the reproduction increases.
That doesn’t mean you can’t make an enlargement to 11X14, which would be only 180 pixels. It just means that larger photo won’t be as crisp. Unless your camera has more than a five-megapixel capacity.
The quality of the final print is directly linked to these three elements:
- The Camera – Look for quality as well as the camera’s megapixel capacity.
- The Printer – A high quality inkjet printer will do just fine.
- The Paper – For photographs, always use photographic paper. Kodak’s Ultima Picture Paper is among the best available.
Once you catch on to the PPI world, you need to learn a bit about “bits.” A “bit” is the smallest unit of information on a machine. The word comes from “binary digit.” It takes eight consecutive “bits” to make a “byte.”
In graphics, a one-bit image is monochrome, whereas an eight-bit image supports 256 colors or grayscales. The number of “bits” used to represent each pixel determines how many colors or shades of gray can be displayed. For example, the color monitor uses eight “bites for each pixel in an eight-bit color mode, which makes it possible to display two to the eighth power, or 256 different colors or shades of gray.
It’s not difficult to learn digital photography or to master the art of photo printing. Check out the free digital photography training lesson from Video Professor®.
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About the Author:
Sheri Graves is an award-winning writer who freelances from her home in Santa Rosa, California.
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