21.10.2010 27.01.2018

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 stored 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 saved image in the future.

When coding in computer graphics, an 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 information about the color of the elements of this image is carried. Each of the cells 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 image pixels, 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 pixels in an image that make up the image vertically and horizontally, physical dimensions are measured in terms of the size of these pixels, which in turn are characterized by the "Resolution" of the image (Resolution - This is a value that is measured in pixels per inch (12cm) it reflects the number of pixels in one linear inch, thus determining their size.

For example, if an image has a resolution of 150 pixels, then this does not mean that there are 150 pixels for every inch (square) of it. But in fact, 150 px are located sequentially in a segment that is one inch long. 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. When fixing the number of pixels that make up the image, when its resolution changes, its physical dimensions also change. An increase in resolution is accompanied by an increase or decrease in the size of the image. When the resolution changes, when there is no fixation of the absolute size, it leads to a change in the number of pixels that make it up, and an increase is the opposite, but the physical dimensions remain unchanged.

It should be noted that a digital image stored in the computer's memory consists of a set of numbers that cannot have any physical dimensions. You can see it using output devices, and this is a monitor or printer. The monitor is a raster device for displaying information on the screen; for this, it uses a fixed grating, which consists of many dots of the phosphor, also called pixels. These pixels are different from the pixels of the image, when the image pixels do not have a fixed size, they can be resized 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 pixels horizontally and vertically i.e. the ones it can display. Basically, for monitors, depending on the size of the diagonal of the screen, it is 640x480 pixels (fourteen inches), 800x600 pixels (Fifteen inches) and 1024x768 pixels (seventeen inches), the working resolution is 72ppi, which is why graphics for websites are created precisely for this 72ppi permission. In new models of monitors, 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 working resolution of the monitor.

An image of a fixed size, say 150x100 pixels on a 72ppi screen will take 2x1.4 inches which equals 5x3.5cm (150 pixels/72 ppi = 2.08 inches, 100 pixels/72ppi = 1.39 inches, 1 inch equals 2 .54cm).

With a screen resolution of 85ppi, the same image would take 1.7x1.18 inches equals 4.5x3cm (150 pixels/85ppi = 1.76 inches, 100 pixels/85ppi = 1.18 inches).

Due to the fact that it is extremely inconvenient to make such calculations to estimate the size of an image on a particular output device, be it a monitor or a printer, so the size of raster images is characterized by resolution. In this case, when creating or scanning an image, not the absolute size is indicated, but its resolution and its physical size.

In this case, the choice of the required resolution is carried out taking into account the output device.

When printing an image, the resolution is selected taking into account the lineatures of the raster of the printing device (printer).

Raster is an image consisting of an array of dots - pixels. A pixel is an elementary, that is, the smallest and no longer divisible element of a two-dimensional digital image of a rectangular or round shape of a certain color. At the same time, a pixel is also a physical element of the matrix of output devices - displays. For example, on a plasma panel monitor, the pixel may be octagonal.

Thus, with the help of such colored dots-pixels, you can create a picture of almost any complexity. Raster format represents images on most graphics output devices: monitors, scanners, printers, cell phones, digital cameras.

The size of a bitmap is the width and height of the drawing in pixels. For example, if we right-click on the picture on this page, we open the context menu and go to "Image Properties ...":

then we will see its dimensions in pixels, where 200 is its width, and 150 is its height:

The number of pixels per unit length is the resolution of the image. The higher the resolution, the more pixels per inch. The smaller they will be. And the more clear the details of the image will be, the more accurate the display of the original will be. Resolution is measured in dpi (dots per inch) - the number of dots per inch.

For a printed photo of normal quality, a resolution of 300 dpi is sufficient. Based on this, it is easy to calculate the size of a digital image in pixels for a certain photo paper format. For example, to fit a photo into A4 (210x297) mm or 8x11 inches, we multiply 8 by 300 and 11 by 300. And we get 2400x3300px. This should be the minimum image size for printing on A4. If the dimensions are smaller, then the image will be fuzzy, blurry.

Now let's move on to the resolution of the monitor. Resolution determines the clarity of pictures and text on the screen. At high resolutions, objects become smaller, appear sharper, and appear larger on the screen. At low resolution, on the contrary, objects look larger and there are fewer of them on the screen.

Cathode ray tube (CRT) monitors, which are no longer used anywhere today, can work effectively in a variety of resolutions. Liquid crystal displays and desktop and laptop monitors based on them are best used at native resolution. Native is the resolution for which the monitor is designed based on its dimensions.

Monitors by aspect ratio are standard 4:3 or widescreen with 16:9, or 16:10. This means that for every four units of screen width, there are three units of height. Or 16 units horizontally with nine units vertically.

LCD monitors have a number of advantages over CRTs. It is compact and light weight. No flicker related to frame rate. No geometric distortion of the image. The high definition of the picture is a consequence of the higher resolution. LCD monitors do not emit electromagnetic waves and are therefore safer. Modern widescreen monitors are available even with a built-in audio system.

Right-click anywhere on the desktop to open the context menu and select the "Screen resolution" line. The Display Settings window will open. Here we expand the "Resolution" scale:

1920x1080px is the native resolution of this 24-inch display. 24 inches is its diagonal. To find out the dpi, you need to divide 1920 pixels by the width and 1080 pixels by the height of the screen in inches. And we get 92dpi. For comparison: a 15-inch CRT monitor is considered optimal resolution of 800x600px, which is 67dpi.

From here - practical conclusions. When we select beautiful wallpapers for the desktop, the size of the picture in pixels should not be less than the set monitor resolution. For example, for the 24-inch monitor shown above, the dimensions of the picture should exceed 1920px horizontally and 1080px vertically. Or be exactly the same size. A smaller image will look blurry and completely unacceptable.

Wallpapers and various images can be selected on a specialized image search engine. An active link is on the page of Internet search engines.

The disadvantage of simple raster images is the large size of the image file. Therefore, raster photographs and drawings are saved in a compressed form in various graphic formats. The choice of format depends on the type of image and how it is used. Optimal for posting full-color photos on the Internet is the jpeg format, for example. However, jpeg is not well suited for drawings, character and text structures. Such graphics are best saved in formats that compress losslessly, like png or gif.

There is much more to write about graphic formats.

And, how easy it is to make a gif-animation yourself - we read the “gif” in the article

Welcome to my blog again. I'm in touch with you, Timur Mustaev. It is possible that everyone had to deal with such a situation: you took a picture, on the screen the picture looked clear and of high quality.

Then you went to the salon and printed it out, and it looked completely different from the one on the monitor screen and had a lot of digital noise. What is the problem? Today I will talk in more detail about this problem and what are the photo formats. Let's start studying.

Basic terms for understanding the topic

Pixels - small square dots, colored in a certain light, which make up a single whole - an image.

When you look at a photograph, the eye does not notice the specific dots of the raster, since they are very small and their number can reach tens of thousands, they merge to form one picture. Only when magnified can you see them.

There is a feature: the higher the number of raster dots, the more details are drawn and the photograph is better.

Linear dimension is the width and height of the printed image, expressed in millimeters. They can be recognized using a regular ruler. For example, the linear size of a picture with parameters 10*15 cm is 102*152 mm.

Parameters in pixels are data about the width and height of the digital image.

There is one feature. Digital cameras take pictures of the same sizes: 640 * 480, 1600 * 1200, and on the monitor we see 800 * 600, 1024 * 768, 1280 * 1024. That is a significant discrepancy.

Consider examples. If the picture has a size of 450×300 pixels, then the picture will be rotated under the album, that is, it will be placed horizontally. What does it depend on? The width of the image is greater than the height.

If we take the size of the picture 300 * 450, then it will be located in portrait orientation, that is, vertically. Why so? The width is smaller than the height.

Resolution is a number that relates values ​​in millimeters and pixels, measured in dpi(from the English "dots per inch" - the number of dots per inch).

Experts advise setting a resolution of 300 dpi, designed to obtain high-quality photographs. The minimum resolution is 150 dpi.

The higher the score, the better the photo quality.

But, it is worth noting that if you make a photograph larger than the original, that is, “stretch the dots”, then the quality drops.

Resolution may vary depending on different camera models. What is the secret? Manufacturers of photographic equipment indicate an inaccurate number of megapixels, for example, 12 MP. In fact, it may turn out to be 12.3 or 12.5 MP. But the print quality will not deteriorate from this fact.

Standard sizes

What are the photo formats? Let's find out.

1. The most popular print size is 10*15 cm. It is used to form a family archive.
2. The next one is 15*20 cm or A5.
3. A4, 20 * 30 cm or 21 * 29.7 cm. Used to decorate walls with photographs. Since A4 is the size of office paper for printing, printing is not difficult, since printers are mainly designed for A4 production.
4. 30*40 cm is a complex format. It has two other names: A3 or A3 +. Why complex? Because there is confusion. A3 size has parameters 297*420 mm, but you cannot pick up such photo frames, they are not on sale. The closest photo frame to this photo is 30*40 cm. Be careful when ordering. Photo frames are made with glass.

Custom sizes

Often we have to order a photo not of a standard size, but of a unique one - non-standard.

1. 13 * 18 cm. It is used extremely rarely. Printing is difficult.
2. 40 * 50 cm or 30 * 40 cm. Pictures with these parameters will help decorate the interior, since they are quite large. Therefore, the quality must be high.

How to calculate dimensions for high resolution

Let's take a closer look at a photo with parameters of 10 * 15 cm.

• The linear values ​​​​of these parameters (usually indicated in special tables) are 102 * 152 mm.
• Multiply the width of the image (102 mm) by the resolution we want to achieve, in our case it is 300 dpi.
• Divide the result of the last step by the number of mm in one inch - 25.4.
• Let's get the number of raster dots of the original image in width 102*300/25.4 =1205.

We will carry out the same algorithm for the height.

152*300/25,4 = 1795.

So, we conclude that for any photograph, the size of which will be greater than 1205 * 1795 pixels, when printed on a format of 10 * 15 cm, the resolution will be more than 300 units.

Sometimes it turns out that images with resolutions of 150 and 300 units look exactly the same. Why is this and what does it depend on? Depends on the genre of the picture and the distance from which it will be viewed.

Documentation

Document formats are measured in cm!

• For different types of certificates - 3 * 4 cm;
• For visas - 3.5 * 4.5 cm;
• For a passport - 3.7 * 4.7 cm;
• In a personal file - 9 * 12 cm;
• Residence permit - 4 * 5 cm;
• For passes - 6 * 9 cm.

Another range of formats

The main thing is that the photo frame matches the photo. Therefore, manufacturers produce special paper with certain sizes:

• A8 (5*7cm);
• A7 (7*10cm);
• A6 (10*15 cm);
• A5 (15*21cm);
• A4 (21*30cm);
• A3 (30*42 cm).

Why choose the right paper? As a result, you don't have to look at an incomplete, cropped image, or crop white margins that are redundant. Usually, the photo salon presents formats for printing with examples.

Order Features

If you place an order via the Internet, the system, when sending the image, says which parameters would be more appropriate for obtaining a high-quality image. If you choose the format of your choice, and not recommended by the program, then the administration does not take responsibility for getting poor quality.

It would seem that in the modern age of digital technology, why print photographs, because most photos are viewed in digital form. Knowledgeable people say that a photograph comes to life only when it is printed on paper, has a frame and hangs in a room to decorate the interior.

Remember that before printing, you need to select certain options that will affect the quality of the printed image.

Subscribe to blog updates and share your knowledge with friends on social networks.

All the best to you, Timur Mustaev.

Here are 5 Frequently Asked Questions About Photography by Aspiring Photographers

How to avoid blurry images?

Here are some tricks to help you avoid blurry photos.

Use the correct shutter speed. There is one simple rule for calculating shutter speed, knowing which will help you take clear pictures when photographing without a tripod. If you are using a 50mm lens then the maximum shutter speed is approximately 1/50s, if you are using a 100mm lens it is about 1/100s, and so on (This rule also works for focal lengths that have been converted from film to 35 mm).

Take a tripod with you. Everything seems to be logical, but many people simply leave it at home. Tripods can be bulky and heavy, or completely light and portable. Dimensions do not affect its effectiveness in any way, so everyone can choose something for themselves.

Use a remote shutter release, or the timer function in combination with a tripod. This guarantees you exactly that your camera will not shake while shooting.

Understanding Image Size and Resolution

The size of an image and its extensions are often stated in units that are difficult to read. Below is a brief overview of the most commonly used units

1. File size, depends on the compression format used to save the image. The file size is specified in KB, or MB. The image in the figure above is a TIFF compression of about 41.4 MB. The same JPEG compressed image would require 15 MB. The file size can vary greatly.
2. Image size in pixels, it refers to the height and width of the image captured by the camera. The Nikon D70 produces images of 3008 × 2000 pixels (that is, 6.1 million pixels, or 6 megapixels). Here, the basic rule is - the more the better.
3. Permissions, is considered in dots per inch (PPI). The resolution of photographs taken on the Nikon D70 is 300 pixels (dots) per inch, that is, when printing an image, we get:
   1. 3008/300 × 2000/300 = 10.02" x 6.66" (24.46cm x 16.93cm)
   2. When printing a single image on an inkjet printer, based on 180 pixels per inch, the image size will be: 3008/240 × 2000/240 = 12.53" x 8.33" (31.83 cm x 21.17 cm).
   3. Printers (and other output devices) have resolution, which is specified in DPI (dots per linear inch). Typically, an inkjet printer has a resolution between 1400 and 5760 ppi. However, we only end up with 180 to 360 dpi as a result, due to the smoothing of the midtones. Inkjet printers are the most optimal printing devices for digital photos.
   4. Prepress still uses LPI (Lines Per Inch) devices.
   5. Monitors have a resolution of 72 to 100 pixels per inch (72 to 100 ppi).
4. Constrain Proportions: always use this option, it will help to avoid distorting your photo.
5. Resample Image: This option is used to get a larger or smaller version of the image, but when enlarged, it results in a noticeable loss of quality. If you disable this option, the image data remains unchanged, and only the physical size of the output (when printed) is changed.

What does the Rule of Three say?

The rule of three is a compositional rule in the visual arts, applied in painting, photography and design. The rule says that any image can be divided into nine equal parts, can be divided along a horizontal or vertical line, and most importantly, that the main compositional elements must be located along these lines, or at their intersection. Supporters of this rule argue that this alignment of objects gives the picture more tension, attracts the attention of the viewer, much more than the usual centering of the object.

Understanding Lab Color

Lab Color is an independent program for performing color transformations. It does not depend on how peripheral devices such as a monitor, scanner, or camera recognize colors. It is directly related to the most advanced optical device - the human eye. Lab Color is used to describe the full spectrum of colors that humans can distinguish.
Lab Color uses three color channels, the L channel - which contains all the information about the brightness, and two color channels - A and B.
The L channel has 100 possible values, ranging from zero, which is black, to 100, which is white.
Channel A consists of magenta and green. A negative value, which ranges from -128 to -1, represents green, and a positive value, from 0 to 127, represents magenta.
Channel B is responsible for yellow and blue. A negative value, from -128 to -1, indicates blue, a positive value, from 0 to 127, indicates yellow. You can control these channels independently and use them creatively to make your photos even more attractive.

What is a Histogram?

Histograms are useful in determining the exposure of an image. A histogram is a graphical representation that shows the number of pixels in an image between absolute white and absolute black.
When shooting, it is very important to be able to read the histogram correctly because it gives you a true picture of what your camera has captured. Each camera displays the histogram differently, but the basic information is the same. Some cameras show a separate histogram for each color channel - for green, red and blue channels, as well as for the entire image as a whole. The histogram shows which color range your image falls into.

Convenient, fast, legally clean:

In our photobank, a lot of images for large-format printing are bought daily, which are successfully applied to photo wallpapers, skins, advertising banners, exhibition stands, 3D floors, stretch ceilings, paintings on canvas, posters, furniture, large-format advertising media, etc. If you are not sure that you will receive the file with the required permission from us, simply