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‏إظهار الرسائل ذات التسميات Pixels. إظهار كافة الرسائل
‏إظهار الرسائل ذات التسميات Pixels. إظهار كافة الرسائل

الأربعاء، 12 أكتوبر 2011

What is PPI – Pixels Per Inch?

الأربعاء، 12 أكتوبر 2011
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The term PPI is not used much. Many people confuse PPI with DPI or have never heard the term PPI. PPI is a measurement of the quality of a print and understanding this term and what the number means can help you determine the right sizes and resolutions for your next digital photo print.

PPI: stands for Pixels per Inch. PPI describes the number of pixels per inch in a photo. PPI is a function of the number of pixels the camera’s sensor supports (also known as megapixels) and the size of the photo. To calculate a photo’s PPI simply multiply the page length by its width in inches. The result is the number of square inches on the page. Now divide the number of pixels the sensor supports by the number of square inches. The result is the number of pixels per square inch. All that is left to do is to find the square root of this number. Following is a table that shows the PPI for various page sizes for a 5 megapixel camera.

page size 4X6 - 456 PPI
page size 5X7 - 377 PPI
page size 8X10 - 250 PPI
page size 11X14 - 180 PPI
page size 16X20 - 125 PPI
page size 20X30 - 91 PPI



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الاثنين، 3 أكتوبر 2011

How to choose a camera with the right number of Mega Pixels?

الاثنين، 3 أكتوبر 2011
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The race for mega pixels has started and there is no way to stop it. Every few months cameras with more pixels hit the market. The manufacturers want you to dump your old camera and buy the newest and greatest one after all aren’t 10 mega pixels better than just 8? Apparently the answer is not that simple.

As with many other things when it comes to mega pixels more is not necessarily better. There are many considerations when buying a camera and the number of mega pixels is just one of them.
One of the most important things to consider is usage. More mega pixels are good for people who plan to print photos (especially enlargements) or for people who need to zoom in and grab fine details from a big photo. If the main usage of the photos is watching them on your computer screen and maybe printing a few 4X6 prints than 2 mega pixels is more than enough (yes… just 2). Most screen resolutions are 1024X768 so even when viewing the photo in full screen mode you can only view 1024X768 < 1 mega pixels. A 2 mega pixels 4X6 photo print will have a DPI higher than 300 which is more than enough for a good quality print.

If you plan to use your photos for enlargements than a rule of thumb is to be able to print at least 300DPI resolution. The following is a table for different print sizes and the needed mega pixels for such print quality:

page 4X6 2MP
page 5X7 3MP
page 8X10 7MP
page 11X14 14MP
page 16X20 28MP
page 20X30 54MP

Another practical consideration is price and budget: Usually the more mega pixels the more expensive the camera is. Unless your budget is infinite when buying a camera you make a compromise between mega pixels and other features. For example is it better to spend money on more mega pixels or on better lenses? Or maybe instead of getting the latest number of mega pixels get an external flash for low light photography? When buying a camera try to predict what and how you will use it. In many cases a lower mega pixels sensor with better a lens will result in a much better photo than a high mega pixels with an inferior lens. Shop around and make sure that you get the best package in terms of mega pixels and other features.

To conclude when shopping for a camera it is best not to be a victim of the mega pixels race. Although it is generally a good thing to have a high number of pixels there are many other factors that influence the quality of the photos taken and the choice of the right camera for you. Lenses, battery life, light sensitivity, sensor technology used, external flash and many other features are not less important as the number of mega pixels. When shopping for a camera make sure that you consider the whole package and not use the number of mega pixels as a “quality” indicator for your buy.



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