Without an understanding of resolution and it's effects, you may find yourself creating awsome images that fill your screen, yet to be small as a postage stamp when you print them. Resolution is a very missunderstood concept in desktop publishing, the confusion compounded by the fact that this term may have entirely different meanings depending on the device you are talking about. As said in the resolution intro, the term resolution represents one of the more elusive concepts of digital imaging. In a vector-based program, we describe an image's size in the popular unit of measures for the country we live in. In the US, we refer to the letter-size page as being 8.5 x 11 inches. Image size in photo-editing programs is traditionally measured in pixels. The reason for using pixels is that the size of an image in pixels is fixed. If we use a unit of measure other than pixel, say inches, the dimensions of the printed image are dependent on the resolution of the image. Resolution is the density of pixels per inch (PPI) that make up an image, and it is measured in dots per inch (DPI) on printers or scanners. In other words, it is a measure of how closely each pixel in an image is positioned to the one next to it. Because printers use ink, wax or such stuff, they produce rounded dots on the surface of the media used for the print. These dots can be smaller or bigger according to the intensity of the color that has to be produced. Now scanners will have to pick up points from an image on such media, the points will be these same dots. That's why we say Dots Per Inch for scanners and printers, and Pixels Per Inch for screens. Let's play with construction blocks. You have a square of resolution 1, this allows placing blocks of size 1, meaning 9 big pixels wide and 9 big pixels high. So, in this square you have now 9 x 9 pixels or 81 pixels. If you now want to put the double of these pixels, you will understand that these pixels would have to be smaller in size, say blocks of size half, because the containing square box will remain the same size. Now if you double the contained pixels, this is said as being double the resolution. the amount of pixels in this case would be 18 x 18 or 324. Why is this not the double of 81, you would ask. Well the container is actually a square, so it's not simply the width and height that doubles, but all the containing squares where the pixels can be put in. So each pixel width and height is doubled, this also means that each original pixel placeholder now holds 4 pixels and not 2 because it's a square. To be clear, if you double the resolution, you don't double the image size but instead of this you double the containing number of pixels, this should, in many cases increase quality but also increase image file size, because that way the image's data is increased. now if you lower the resolution, you lower the contained pixels, so you also lower the quality by reducing the number of pixels. The program will try to divide each pixel by 2, meaning that each group of 4 pixels will be calculated to produce 1 single pixel that would have a color similar to the original 4 pixels colors. Here it is clear that this lowers the grafics quality, because 1 pixel information would have to look like 4 color informations. Image format compressions work much similar way. They calculate pixels having approximately the same colors, then blend this information making it a square, these are the big separation squares you can notice in very low compression quality. When we want to print some info on paper, let's say an image the resolution is explained completely different from screens. First of all, printers don't work with the Red Green Blue model but instead of this they work with Cyan Magenta Yellow K(black). Now, printers don't have color cannons, but the have ink cartridges. The printer head spits the ink to the paper in rounded dot form. You would ask, why are they rounded dots and not squares ? Well, there's a very good reason to this. The reason to use rounded dots instead of square forms is that the rounded dots can vary in size and melted easely togheter when this is needed to produce a color blend. Now, for the ease of understanding this, i will not start explaning how blended colors are produced, but instead of this i will try to explain how one single color intensity is produced. If you want to produce a square of just plain yellow, then the printerhead will only spit yellow ink at the paper and make all the dots have size 1. If you intend to make the same square with a more pale yellow, then the printer will receive different data from the photo-editor program. The info sent to the printer will be more like producing smaller dots of the yellow ink, the smaller the dots on the paper, the bigger the blank left paper space, this produces a look of half paper white and half yellow ink at that place on the paper. Let's explain now how color blending works with printed color dots. As the example above we will start with a single plain color. If you made some green square, the printer cartridge does not contain green ink. So it is simulated or made up by 2 colors, these are Cyan and Yellow. Here we have a plain color, so the dots of Cyan and Yellow will have equal size. If you want to produce a square that is more blueish, then the Cyan dots will have a bigger size then the Yellow dots, as example, Cyan 75% and Yellow 25%. This all can be done because the ink is translucent and not plain like paint.