Article, September 2007
by Bill Moeller, President
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Our August meeting reminded me once again that this group’s most valuable resource is its members. I was amazed (a sign of incipient senile dementia?) at how much we know collectively, and how easily that knowledge is transferred at our ever popular Q&A sessions.
Interest, as usual, was high and participation so good that we ran out of time and had to shut the meeting down with some unanswered questions hanging fire. One of these had to do with resizing digital photographs. Resizing can be somewhat confusing because, to (mis)quote a rather well known political figure, “It all depends on how you define size.” Size can mean number of pixels or it can mean the physical dimensions of the image, both of which determine, or are determined by the number of pixels per inch (ppi). The relationships are: (1) width in pixels x height in pixels = total pixels; and (2) pixels per inch = width or height in pixels divided by the same dimension in inches.
The reason for resizing is usually to reduce uncompressed file size for storage or transmission, or to size the image properly for printing or other display. For example, my camera produces images which measure 2560x1920 pixels (roughly 5 megapixels), or 35.556x26.667 inches at 72 pixels per inch. If I want to email one of my shots for viewing in the email message, I will probably resize it to 5.33x4.00 inches at 100 ppi so it will show at roughly that physical size on the monitor. (Note that this reduces the number of pixels in the image to 533x400, or 213,200 pixels.) If I want to send an image which can be satisfactorily printed at that size, I will probably resize to 5.33x4.00 inches at 200 ppi because that is the minimum ppi most printers require for a decent print. (This image will measure 1066x800, or 852,800 pixels, will take longer to send, and will show up on the screen at about 10.66x8.00 inches.)
Resizing is not difficult. Most image processing software gives you direct control over the three size factors above, and all you have to do is decide on two of them and the software will determine the third. Just remember that once you reduce the number of pixels in an image, that information is lost forever—unless you follow the golden rule of never, never modifying the original image file.
Shift gears: please remember that our next program will be a group discussion on lost email. This will be like a Q&A, but with a specific chosen topic. Please bring your email experiences to share with the group, particularly if you have had problems and found a solution, or are having problems and are looking for a solution.
See you on the 15th.Click here to return to top