About – Images and image processing

People that are new to the field of digital images are ofter confused by the formats, and resolutions of digital images. I will attempt here to lend some clarity to the subject for beginners.

Image formats: There are four image formats in common use. They are .bmp, .tif, .jpg, and .png.

.bmp – Is the standard image format adapted by “Windows”. It is a non compressed format and images can be copied a recopied many times without incurring any degradation of images.

.tif - Is a image format commonly used on MAC's although in recent years it has broad acceptance on other platforms. It is a non compressed format and images can be copied a recopied many times without incurring any degradation of images. I use this format for images I plan on processing.

.jpg – Is the image format commonly used in digital cameras. If you are going to process these images you should first convert them to .tif or .bmp as processing of .jpg images and then re saving to the . jpg format is a lossy process which degrades the image each time it is processed.

.png – This format is commonly used on Linux systems. It is an uncompressed format which has compatibility with most Linux programs. Some “Windows” programs have .png compatibility but not all.

Resolution: - is the other characteristic of images which confuses the beginner. Most digital cameras today produce images that are 3000x2000 pixels or larger if the maximum camera resolution is being used. Even the most sophisticated monitors today (1920x1080) cannot display these image full sized as the camera image is larger than the screen. These images must be re sized for screen viewing but I suggest you always use your camera in the highest resolution as these images can always be resized downward if that is what you require but if images are re sized upward they have no greater quality than the original.

You should archive your camera images by copying the original camera file without processing or conversion and if you are going to process a image always work on a copy of the original.

There are many pieces of software for viewing images re sized to the computer screen some of which do a notably poor job of resizing. The “Windows Picture and Fax Viewer” which is default viewer for “Windows” to my mind is one of the worst. To get a good rendering of high resolution camera images I wrote the program MHview which displays the image as large as the users screen will allow and it displays on a black background as a white background on a computer monitor destroys the perception of contrast and brightness of the image.

For Internet use you want to create images that can be viewed on screen without being re sized this means the images should be less than 800x600. To reduce the size of the image file it should be saved in the .jpg format which is compressed. I have written a program called MHconvert  which has a feature that allows for conversion of batches of images to low res .jpg's for internet use.