Pixel(Pixel) – the smallest element of a two-dimensional image in raster graphics.
Each smallest element has its own color, brightness and, possibly, transparency.
Let's see under magnification what it looks like " pixel grid».
An example image is available.
The number of pixels determines the level of accuracy, detail of the image (photo) and resolution value.
The number of pixels is related to the amount of megapixels in the camera parameters.
If the camera has 18.7 -megapixel camera, then the maximum size will be 5184 X 3436 , this means that the photo will have 5184 pixels in width and 3436 in height.
Permission
The pixel size of an image measures the total number of pixels in width and height.
Permission(Resolution) – a value that determines the clarity of the details of a raster image. Most often it is set in pixels per inch (Pixels Per Inch / PPI).
How more pixels per measure, the higher the resolution.
The higher the resolution, the better quality print.
Note
In Photoshop, you can look at the ratio of size and resolution of an open image by going through the menu “ ” ( / Keyboard shortcut “ Atl+Ctrl+i»).
Let's look at the difference in resolutions using an example.
Below is 2 photo options with different resolutions.
When creating a document in Photoshop ( File – New| / Keyboard shortcut " Ctrl+N") you can set the parameter " Permission"(Resolution).
We looked at the concepts of "pixel" and "resolution" in relation to raster images and Photoshop programs.
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Have you ever been disappointed after printing a picture from the Internet? The images looked great on the computer screen, but they were either postage stamp sized or large and blurry. The culprit here is the picture resolution.
In fairness, it must be said: the permit was not invented to ruin our lives. The real reason for poor print quality is the very small pixel sizes of most images on the Internet: usually 640x480 pixels or even smaller, thanks to which they are quickly and efficiently displayed on a computer screen and loaded on websites.
What can we do to ensure that when printed, pictures from the Internet look as good as photos from a digital camera, and are of a decent size? The answer is simple: absolutely nothing. Most pictures don't have enough pixels to print high quality. Let's try to figure out why.
First of all, let's forget about downloading pictures from the Internet: by doing this, we violate copyright.
Let's look at the image resolution in general.
Resolution is a value that determines the number of dots (pixels) that fit in each inch of paper when printed. Obviously, since each image has a fixed number of pixels, the more you try to fit into one inch of paper, the smaller the resulting image size; The fewer pixels in one inch, the larger the image will be printed.
The concept of Resolution completely relates to printing, but has nothing to do with displaying an image on a monitor screen; that's why everything always looks bigger and better on the screen.
For example, consider this photo:
I can't help but smile every time I look at her. I took a photograph of this horse while driving through the countryside one day. As a rule, she always stands proudly, imperiously, her appearance is full of dignity and grace. But that day I found her in a completely ridiculous position: she was bending over somehow, a straw was tangled in her mane, and it seemed like the horse was chewing something. Or maybe she's trying hard to smile at me? Anyway, we'll take her photo as a reference.
First you need to check the size of the photo in Photoshop through the menu Image > Image Size (Ctlr + Alt + I). The dialog box that opens displays full information about size:
The Image Size dialog box is divided into two parts: the upper one is called Pixel Dimensions, the lower one is called Document Size. Dimension shows the width and length in pixels, and Print Size shows the actual dimensions of the image when printed on paper.
In the Pixel Dimensions subsection it is indicated: the width of our photo is 1200 pixels, the height is 800. This sounds like a lot (multiplying the width and height values, we get as many as 960,000 pixels in the picture!) Yes, this is really a lot for a monitor screen. A photo of this size may not fit on the screen! But, unfortunately, this does not mean that the print quality will be high. Pay attention to the Print Size subsection:
Here we will find information about the current resolution and the size of the image on paper. The resolution of the photo we are currently looking at is 72 pixels. This means that of the 1200 pixels that make up the width of the image, 72 will be printed on each inch of paper; Of the 800 pixels that make up the height, 72 will also be printed on each inch.
The value in the Resolution field applies equally to the width and height, but not to the total number of points. In other words, for every square inch of paper, 72 pixels from our image will be printed from left to right, and 72 pixels from top to bottom. The total number of pixels on each square inch of paper will be 5184 (72x72).
Let's do a little math to make sure the image's width and height are displayed correctly in the Document Size field. We know the width of the image is 1200 pixels and the height is 800 pixels. Permission to this moment is 72 pixels per inch; to find out the dimensions on paper, you need to divide the number of pixels making up the width by 72; height is calculated similarly.
Width (1200 pixels) divided by 72 pixels per inch - 16.667 inches
Height (800 pixels) divided by 72 pixels per inch - 11.111 inches
So, the image size on paper will be 16.667 x 11.111 inches.
Let's look at the Document Size subsection again:
The dimensions are exactly as indicated! How big will the photo be, right?
Unfortunately, it's not that simple. This resolution is not enough to display the necessary sharpness and good quality when printing. Take a look at the image below: This is what the photo would look like if printed at 72 pixels per inch.
Try to imagine the quality at 11 x 16 inches.
Now the dots are too far apart, so there is no sharpness or detail. The quality is dull, too soft and therefore unattractive. Everything looks different on the screen: monitors are low-resolution devices. Even a photograph of relatively small sizes, for example, 640x480 pixels, looks great on them. However, printers are devices high resolution, and for high-quality printing you would need a value much higher than 72 pixels per inch.
How high should the resolution be to get a quality professional print? The generally accepted value is 300 pixels per inch; When printed, the pixels are very close to each other, making the image appear clear. You can even use a resolution of 240 pixels per inch and that will be enough.
Let’s change the resolution of our photo: in the Resolution field we’ll set it to 300. Please note that in the Pixel Dimensions subsection the values of 1200 and 800 are preserved.
Increasing the resolution from 72 to 300 pixels means that out of 1200 pixels of width, 300 pixels will be printed in each inch of paper, and the same amount of 800 pixels of height. With this compression, the photo on paper will be smaller in size. Therefore, under Document Size, the photo size is now 4 inches wide by 2.667 inches high.
Let's resort to mathematical calculations again:
Width (1200 pixels) divided by 300 pixels per inch - 4 inches
Height (800 pixels) divided by 300 pixels per inch - 2.667 inches
That's right!
The photo when printed will be much smaller in size than with a resolution of 72 pixels, but much better - we will enjoy a clear and well-detailed image.
Of course, no one will print photos at such non-standard sizes as 4x2.667 inches. How to get a high-quality 4x6 photo? We will have to turn to calculations again.
Let's say you took some pictures of a family vacation with a digital camera and want to print them so that the size of the photos is 6x4. We now know that to achieve professional print quality, you need a resolution of at least 240 pixels per inch (300 is better).
Let's look at both resolutions and decide which one is better. At 240 pixels/inch, the width and height will be as follows:
240 pixels multiplied by 4 inches in width - 960 pixels (width).
We multiply 240 pixels by 6 inches in height - 1440 pixels (height).
Total quantity: 960x1440 – 1382400.
So, the photo size should be 960x1440. Nowadays, most digital cameras have a resolution of 5 MP (megapixels or millions of pixels) or higher, so in this case It won’t be a problem to print a 4x6 inch photo even at 300 pixels/inch. The pixel dimensions will be 1200x1800 (total 2160000).
What to do when you need photographs that are not 4x6 inches, but 8x10?
240 pixels times 8 inches is 1920 pixels.
240 pixels times 10 inches is 2400 pixels.
Total: 1920x2400 – 4,608,000 pixels.
So, to print a photo in good quality 8x10 inches in size, its pixel size should be 1920 pixels wide by 2400 high (or vice versa), and the camera resolution should be about 4.6 million pixels.
Digital camera with a resolution of, for example, 4 megapixels will not give the required 4.6 megapixels, so it will not be possible to print photos from such an 8x10 camera with a resolution of 240 in high quality.
To print a photo measuring 8x10 inches and resolution 300 you will need:
300 pixels times 8 inches is 2400 pixels high.
300 pixels times 10 inches is 3000 pixels wide.
The total number is 7,200,000 pixels.
This is already real a large number of points!
To print an 8x10 inch photo at 300 pixels/inch resolution, it would need to be 2400 pixels wide by 3000 pixels tall (or vice versa), for a total of 7.2 million pixels. This is quite a lot, and the camera must have a resolution of at least 7.2 megapixels! Don't forget that photos sometimes require cropping. Therefore, I highly recommend purchasing an 8MP camera!
Raster graphics are like a mosaic consisting of elementary particles - very small colored squares of the same size (i.e. pixels). When an image is saved on a computer, the computer, in addition to information about the number of pixels that make up the image and the color of each of them, must receive information about their size in order to accurately reproduce the image it has saved in the future.
When encoding in computer graphics The image is understood by the computer as a table, which consists of small cells of the same size, each of which is assigned a color value depending on the area it occupies. When an image is processed, the computer remembers the identified image table, the cells in which contain information about the color of the elements of this image. Each cell of such a table is called a point, and the entire table is called a raster.
Note: since the concept of points, as well as pixels of an image, is the same, it is customary to measure any image in pixels.
In addition to measuring in pixels or absolute size, it can also be characterized by physical dimensions. It is worth distinguishing between these two concepts. While absolute size can only measure the total number of image pixels that make up the image vertically and horizontally, physical dimensions are measured taking into account the size of these pixels, which in turn are characterized by the “Resolution” of the image (Resolution is a value that is measured in pixels per inch (12cm) it reflects the number of pixels per linear inch, thus determining their size.
For example, if an image has a resolution of 150 pixels, this does not mean that for every inch (square) there are 150 pixels. But in fact, 150 px are located sequentially in a segment that is one inch long. And a square inch naturally contains 150x150 = 22500 pixels. Three inextricably linked concepts are “the size of an image in pixels, its resolution and its physical dimensions. By fixing the number of pixels that make up an image and changing its resolution, its physical dimensions also change. An increase in resolution is accompanied by an increase or decrease in image size. When changing the resolution, when there is no fixation of the absolute size, it leads to a change in the number of pixels composing it, and an increase is the opposite, but the physical dimensions remain unchanged.
It should be noted that digital image stored in computer memory consists of a set of numbers that cannot have any physical dimensions. You can see it using output devices, such as a monitor or a printer. The monitor is a raster device for displaying information on the screen; for this, it uses a fixed grid, which consists of many phosphor dots, also called pixels. These pixels differ from the pixels of the image when the pixels of the image do not have a fixed size; their size can be changed by changing the image resolution; the size of the screen pixels is fixed; it is determined by the working resolution of the screen.
In a monitor, resolution depends on the geometric dimensions of the screen and its resolution. Screen resolution measured in horizontal and vertical pixels i.e. those that he can display. Basically, for monitors, depending on the size of the screen diagonal, it is 640x480 pixels (fourteen inches), 800x600 pixels (fifteen inches) and 1024x768 pixels (seventeen inches), working resolution is 72ppi, which is why graphics for websites are created using this 72ppi resolution. In new monitor models, this resolution reaches 80-85ppi. When displaying an image, each screen pixel is assigned an image pixel; the size of the image, or rather its area, is determined by the absolute size of the image, the geometric dimensions of the monitor screen and the operating resolution of the monitor.
An image of a fixed size, for example, 150x100 pixels with a screen resolution of 72ppi will take 2x1.4 inches, which is equal to 5x3.5cm (150 pixels/72 ppi = 2.08 inches, 100 pixels/72ppi = 1.39 inches, 1 inch equals 2 .54cm).