Resolution affects the amount of discernible fine detail
in an image. A low resolution image looks coarse.
A high resolution image looks smooth.
It is like comparing burlap to silk.
Computer images are made of dots. The more dots per inch (dpi), the higher the resolution. Printers range from 300 dpi to 2400 dpi. Check your printer specifications to find its resolution. On the computer screen, the dots are called pixels. We generally use dots per inch and pixels per inch (ppi) interchangeably. Monitor resolution is usually around 70 to 100 dpi.
A high resolution image is made of more tightly packed together dots. More dots in the image means a larger file is created.
Color depth refers to the number of colors that can be displayed by each pixel. In the computer world, that relates to the bits of information that are stored about the color of each dot or pixel that makes up the image. True color (32 bit) can store millions of bits of color information per pixel. The next step down is 24 bit color which is still millions of colors. Next is 256 colors (8 bit) and then, black and white (1bit).
The more bits you store, the larger the file. So if you are scanning an image that is only made of black lines on white paper, you should not use the true color (32bit) setting because the file will be much larger that it needs to be.
There are three common graphic file formats-TIFF (tif file extension), GIF (gif), and JPEG (jpg). The Web uses JPEG, GIF, PNG and new file type (released April 2001) called SVG (Scalable Vector Graphic). You also might also use BMP image files. BMP's are Windows Bitmaps and are a common Windows image file format. You can find thorough explanations of each file type on the web. We are going to cover the basics.
To make files smaller, compression can be used. Lossless compression saves the data and packs it more tightly together. The other option is to lose some data when the file is compressed. JPEG uses this lossy (rhymes with bossy) compression to achieve very small file size. The more you compress a JPEG, the lower the image quality.
TIFF or TIF
TIF is a good format for master copies of images. It is widely supported by image editing software. It uses lossless compression which means when a TIFF file is saved, no image information is thrown out. This also means the files can be large.
GIF (pronounced "Jif" or "Gif")
GIF format is best for saving images with few colors. GIF can store and yield up to 256 colors. This works best for something like our K-State Research and Extension Logo. GIF files are smaller than TIFF and higher quality than JPEG if the image contains few colors. GIF is not an appropriate file type for storing photographic images. GIF files are viewable in web browsers and GIF is common format for web icons and clipart.
JPEG or JPG (pronounced "Jay-Peg")
The JPEG format is the king of compression. JPG is the most common format for viewing images on the Web. JPEG images are small for fast delivery over the Web and are also the most common format saved in digital cameras. A word of caution, don't save JPG's over and over because the images get compressed over each other and lose significant amounts of image detail and information. JPEG uses lossy compression. The good news is that a high quality JPEG is often 1/10 the size of a TIFF. If you are going to send an image via e-mail, it should be as small as possible without affecting image quality.
Avoid opening and saving a JPEG file multiple times since a JPEG file loses some quality each time. It is a bit like making a video tape copy from a copy. Every generation is of lower quality. If you will be editing an image, don't save your master or archive as JPEG. If you need to edit an image, save the intermediate image as TIFF. If you want a master copy, keep it in TIFF and you can always save a JPEG file later for email or for placing on a web page.
More information on Web Formats:
When was the last time you calibrated your monitor?
Monitors change color and brightness over time. There are several tools available to calibrate what you see on your monitor so it matches your digital images for print, computer presentations, and the Web.
If you own Adobe Photoshop, use the Adobe Gamma program located in the Control Panel. More info. .
Free Internet Monitor Color Calibration at EasyRGB