Widescreen image sizes. Lesson: Image Resolution
14.06.2016
Almost everyone takes photos now, and everyone is familiar with the term “resolution”. But not everyone knows exactly what this word means. Resolution refers to the number of dots per inch.
The dots that make up photos are called pixels. The law here is very simple: the greater the number of these same pixels in one inch, the higher the image quality.
Resolution allows you to judge the quality of the process of creating an image and the detail of the picture. In modern photography, this term is directly related to the digital format of photographs. But it can also be found where it is, for example, photographic paper or film.
What does "high resolution" mean?
If we talk about high resolution, then we mean high degree detail. Any professional photographer knows very well that resolution, that is, the number of dots per 25.4 mm (which is equal to 1 inch), is denoted by such an abbreviation as "DPI" (see the article about).
If the image resolution is 300 DPI, then we can say with confidence that these photos are of good quality. Based on their experience, photographers say that the resolution allowed for printing images must be at least 150 DPI.
When printing photos, the most common formats are 9 by 13, 10 by 15, 13 by 18 cm, etc. For each of all these formats, there are specific linear dimensions in millimeters. If we take the format into account, then it is easy to calculate the optimal image dimensions in pixels in order to eventually get an extension of 300 or more DPI.
If we take a photograph 9 by 13 cm, then its linear dimensions will be: 89 by 127 mm. We multiply the height in millimeters by the resolution we need and divide by 25.4 mm (see above). We get: (89 * 300) / 25.4 = 1027 - this is the number of pixels in height we need to have in the original image (photo). We do the same with the calculation of the width (127 * 300 / 25.4 = 1500).
Based on this, we understand that when printing a photo of a 9 by 13 picture, which is larger in pixels than 1027 by 1500, we will receive a photo with a high resolution (above 300 DPI).
But, as practice shows, often images with an extension of 150 DPI look no worse than the same photo, but with a higher level of extension - 300 DPI and higher. Here, much depends on the distance from which this image will be viewed and what exactly is depicted on it.
Interesting publications on the site
Many of us love to take pictures. Variety and availability digital cameras make photography a popular pleasure, allowing us to capture the bright, colorful moments of our lives. Wherein high quality received photographs does not guarantee the same quality when printed digital pictures on standard roll photo paper. In this material, I will tell you what sizes of photographs are for printing, give tables of available formats, and also give a number of examples that allow you to clearly understand the features of different photo sizes.
Dealing with photo sizes for printing
To understand what are the sizes of photographs for printing and what are their specifics, we need, first of all, to understand basic concepts needed to understand the digital printing process.
Linear photo size– photo dimensions in millimeters (width-height).
Photo parameters in pixels- the dimensions of your photo, expressed in the number of pixels (width-height).
Pixel- the smallest element of the image, usually a point of a rectangular or round shape, and a certain color. An image is made up of hundreds and thousands of such pixels, which are counted both horizontally (width) and vertically (height). For example, an image size of 1181x1772 (usually corresponding to the standard photo size of 10x15) is 1181 pixels wide by 1772 pixels high.
Moreover, the more such dots-pixels in your image, the usually it is of better quality, with better detail and drawing of objects.
Side proportions- the ratio of the dimensions of the sides of the photo (for example, 1:1, 2:3, 3:4, and so on). The parameter shows how much one side is shorter or longer than the other.
Bitmap (bitmap)- an image consisting of such pixels.
DPI- (abbreviation for "dots per inch" - dots per inch) - a parameter used to characterize the resolution of printing photos, that is, the number of dots per inch (an inch is 2.54 cm). The basic print standard is 150 dpi, the optimal one is 300 dpi. Accordingly, the higher the DPI, the higher the print quality of the existing digital photo.
Standard (format) photo- this is a template aspect ratio of a photograph, which is important to adhere to in order to obtain the final image on paper.
Why is it important to consider standard photo sizes?
In the vast majority of cases, the digital images you receive will be printed on photo paper that has standard sizes. If the proportions of digital images and the selected photo paper sizes do not match, the photos may come out stretched, not clear, lose image quality, or have other undesirable consequences for you.
Therefore, it is important to compare standard photo print sizes with the pixel dimensions of your digital photos in order to select the optimal print format.
Popular photo sizes for printing with a table of formats
The generally accepted standard for a photo is 10 by 15 cm. At the same time, the size of a proportional digital photo is usually slightly larger (for example, 10.2 by 15.2 cm), and the size in pixels of this photo will be 1205 by 1795 pixels.
Other formats are shown in the table below:
If you plan to work with large format printing, then it has fairly broad requirements for a digital image:
If you know the dpi parameter and the number of pixels of your photo, then using the formula below, you can calculate the required dimensions of the sides of your photo:
In this formula:
x - the size of one side of the photo we need in centimeters;
r – resolution of the photo side in pixels;
d - 2.54 cm (standard inch value);
dpi - usually 300 (less often - 150).
For example, let the image width be 1772 pixels and dpi=300.
Then 1772*2.54/300=15.00 cm across the print width.
Popular photo formats
In addition to the classic size 10 by 15 (A6 format) that I already mentioned, there are other popular photo sizes for printing. Among them, I would highlight the following:
Conclusion
This article provided standard photo sizes for printing, popular photo formats, as well as a convenient formula for calculating the optimal size of the sides of a photo. I recommend sticking to the formats I have given, this guarantees the quality of printed photos, and hence the visual pleasure of viewing them.
This is not so much a translation as a retelling of an article published on the website www.luminous-landscape.com.
What is the resolution of my camera?
What should be the resolution of the photo?
Whether to post a photo high resolution in the Internet?
If the image consists of dots smaller than this limit, it appears to the eye to be continuous, continuous. The entire printing industry has been built on this feature of the eye for decades. Every photograph and every picture you see in any book, magazine, calendar, art print, is made up of dots of paint with a resolution typically ranging from 70 to 300 (occasionally more) dots per inch.
Timiryazevsky park by moonlight.
Digital images, whether they come from a digital camera or are scanned, are subject to the same rules. If the print resolution was too small, then we "see dots". This happens, for example, when you look at a poor quality photograph in a newspaper.
What we end up seeing is pixels. These are the discrete elements that make up the image created by the optical system of a digital camera or scanner on a sensor. Pixels are the equivalent film grain. The problem arises when we try to understand the relationship between what is photographed and what will be printed.
This picture shows the menu item dialog Image->Size in Photoshop for the photo "Timiryazevsky Park in the Moonlight", which you saw a little higher. It was obtained using digital reflex camera Canon EOS 300D.
(What follows applies equally to scanned images. The principles are the same.)
The information at the top of this window tells us that the camera took a picture 3000 pixels long and 2040 pixels wide. The image size is 17.5 megabytes.
The bottom section of this window shows that the current settings for this image are 25.4 x 17.3 cm, and that the resolution for this image is 300 dpi. Please note that in the box Resample Image there is NOT a checkmark at the bottom.
Photo start and end resolution
If you try to change only one of these values - length, width or resolution ( Width, Height or Resolution), then the other two will change simultaneously. For example, you made the length equal to 20 centimeters, but the width changed to 13.6 centimeters, and the resolution became equal to 381 ppi, as seen in the picture below.
This happens because in itself the digital image does not have an absolute size in centimeters and does not have a resolution. Its only characteristic is the number of pixels in length and width. It does not have measurements in centimeters or inches. Obviously, the resolution will change depending on the physical dimensions of the image, because the number of pixels will be distributed over a larger or smaller area. The resolution changes according to the size.
Now let's say you want to print this photo in a "very large" size - say 60x40 cm. But in reality you will have to stop at something like 50x33 cm, because the resolution of the image will drop to 155 ppi. Even this resolution is not enough for high quality printing, as we will see below.
Free extra pixels
Actually, nothing is completely free, but you can still get some additional permission if you need, but within certain limits. You probably noticed that at the bottom of the Photoshop dialog box there is a special box at the bottom (“checkbox”) called Resample Image. If you check it, then photoshop disengages
rigid relationship between length, width and resolution (between the values Width, Height and Resolution). By checking this box, you can change each parameter independently.
That is, when this checkbox is checked, you can set the image any size and any permission- whichever you want! Well, isn't it a miracle?
In this example, I ordered Photoshop to resize the image to 60x40 cm, and so that the resolution is 360 ppi. But, as you can see at the top of the dialog box, doing so will increase the file size to 140 megabytes, and the original image "weighed" 17 megabytes.
Where did this extra resolution and all those extra bits in the image come from? They were invented by photoshop. In the same way, when scanning a scanner with a resolution greater than its real optical resolution, scanner composes additional pixels that he is not really able to see. Both the scanner and Photoshop, based on real data, compose additional pixels to insert them into the gaps between the “real” pixels. There is no additional information in these "fake" pixels.
"OK then", you might say, " these pixels do not new information. On a fig then insert them?"
In fact, if you do this in moderation, you can make an image larger than the original, and at the same time visually it will be perceived quite well. Usually such "fake" pixels are inserted when an image is going to be shown from a distance (for example, a billboard or a poster), and this effect is almost imperceptible. But if you look at such a picture up close, then its quality will not please you.
The key point here is moderate doses! There is another alternative to Photoshop - this is a separate program called Genuine Fractals. It uses a completely different mathematical algorithm than the one Photoshop uses. As far as I know their discussions in various forums, Genuine Fractals does this operation much better than photoshop.
But in any case, the larger the original image in pixels (and the better its quality!), the more you can stretch the image (or increase its resolution).
And finally, sometimes you may need to reduce the resolution.
If you are preparing a picture for posting on the Internet, then you will have to set the standard screen resolution to 72 ppi. You need to check the box Resample Image, enter value 72 ppi, and then specify the desired length and width in pixels ( Width and Height) - so that the picture fits on the monitor screen. Photoshop will discard the extra pixels and create a file of the appropriate size.
What permission do you need?
The final question: what resolution will be enough? The answer depends on the device on which your image will be displayed or printed. For example, pictures on a monitor screen usually need 72 ppi. For photo frames - even less. If the file has a higher resolution than required, then you simply will not see the difference on the screen. (The image may even look a little worse - it depends on what program the image is displayed on the screen). But the main trouble here will be that a large file will simply take longer to load. That's all.
Cool printers in good labs require a different permit. For example, the LightJet 5000, a very popular wet printer, requires files with a resolution of exactly 304.8 PPI. Ask your favorite photo lab what resolution you need for high-quality printing on their equipment.
Inkjet printers
Most amateur photographers today print their photos on home inkjet printers. Very popular are printers of the family Epson Photo, so I'll take them as an example. In the specifications of these printers, for example, for models 870/1270/2000P, it is indicated that they print at a resolution of 1440 dpi. This means that they can put 1440 dots on one inch.
But!
They use 6 different colors to print color images. Therefore, each pixel of the image will actually be printed using several dots of a different color - two, three, or even all six colors. Therefore, your printer will have to print more dots than there are in the image.
If you divide 1440 by 6 you get 240 . This is the real minimum image resolution that is needed to get a high-quality photorealistic image on Epson printers that have a resolution of 1440 ppi according to the passport. Many printer owners (including me :) believe that a 360 ppi output file will give slightly better quality than 240 ppi. True, if I make a print of a large format (A3, for example), I rarely make a resolution of more than 240 ppi - anyway, large prints are not considered at close range.
PPI and DPI
Notation PPI(Pixels per Inch) and DPI(Dots per Inch) are often used interchangeably. Actually, this is not true, but this is not a big problem, because usually we understand what we are talking about.
To be absolutely accurate, let me remind you that when it comes to scanners, digital cameras and monitors, it is correct to talk about PPI, and the characteristics of printers and plotters are indicated in DPI.
Now you know exactly the difference.
Final Thought
Here we talked about such concepts that are easier to feel by playing with them in Photoshop or other software than to learn them from printed text. So really, try to play around with the size and resolution in Photoshop, increasing and decreasing the size of the image, evaluating the result by eye.
And finally, when you save your files after resizing and resizing, always make sure that your original file with original dimensions and res will not be overwritten. Only when the original is securely stored in a secluded folder on the disk, you can start experimenting with changing the resolution.
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Pixels, in turn, are a set of dots. And the photo consists of these dots, each of which has its own color and shade. The more dots, the deeper and better the image will be.
Any image a person perceives by sight. And vision is limited even in the most healthy people. And this limitation is about 70 dots per 1 cm or 200 per 1 inch (as resolution is usually expressed). If there are more points in a centimeter, then the human eye will perceive them as a solid line.
What is DPI?
It is on the possibilities of vision that the printing principle is built. Almost every illustration printed matter has a resolution of 90 to 300 dpi. This dependence is called dots per inch or DPI for short.DPI only matters when the image is printed directly. A photograph that is on a computer screen does not have a specific size: length and width. And as mentioned earlier, these two parameters are the main ones when calculating the extension.
The main task of the extension is to take a high-quality picture when it is printed on a printer.
How to take a good quality photo?
To prepare a photo for printing, you need to make some settings in the photo editor. The most suitable editor is Photoshop. After you open the photo in the program, go to the "Image Size" section.The window that opens will show three main fields: width, height, and resolution. When you change the resolution, the height and width will change, and vice versa. If you check the box next to "Track changes", then you can adjust the dimensions independently of each other.
The optimal resolution for a good photo, which is supported by most printers, is 300dpi. But the smaller the image should be as a result, the less resolution you need, and vice versa. Before printing a large format photo, take an interest in the characteristics of the printer: the main parameters are PPI (maximum possible resolution) and the number of colors used in printing. To reveal the true DPI value of a device, divide the PPI by the number of colors.
Have you ever printed a picture from the Internet and felt disappointed? The images on the computer screen looked great, but they were either the size of a postage stamp or large and blurry. The culprit here is image resolution.
In fairness, it must be said: permission was not invented in order to spoil our lives. The real reason for poor print quality is the very small pixel dimensions of most images on the Internet, typically 640x480 pixels or even smaller, which makes them quickly and accurately displayed on a computer screen and loaded on websites.
So what can we do to make prints from the Internet look as good as photos from a digital camera and be a decent size? The answer is simple: absolutely nothing. Most of the pictures do not have enough pixels for high quality printing. Let's try to figure out why.
First of all, let's forget about downloading pictures from the Internet: by doing this, we violate copyrights.
Let's look at image resolution in general.
Resolution - 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 will be; the fewer pixels in one inch, the larger the image will be printed.
The concept of Resolution is fully related to printing, but has nothing to do with displaying an image on a monitor screen; that is why everything on the screen always looks bigger and better.
For example, consider this photo:
I can't help but smile every time I look at her. I took a picture of this horse while driving through countryside. 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 pose: she somehow bent over strangely, a straw was tangled in her mane and it seems that the horse is chewing something. Or maybe she is diligently trying to smile at me? In any case, we will take her photo as a sample.
First you need to check the size of the photo in Photoshop through the menu Image> Image Size (Image> Image Size) (Ctlr + Alt + I). The dialog box that opens displays the full size information:
The Image Size dialog box is divided into two parts: the upper one is called Pixel Dimensions, the lower one is 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, our photo is 1200 pixels wide and 800 high. Sounds like a lot (by multiplying the width and height values, we get as much 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 looking at now is 72 pixels. This means that out of the 1200 pixels that make up the width of the image, 72 will be printed on every inch of paper; Of the 800 pixels that make up the height, 72 will also be printed per inch.
The value in the Resolution field applies equally to the width and height, but not to the total number of pixels. 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 width and height are correctly displayed in the Document Size field. We know the width of the image is 1200px and the height is 800px. The resolution is currently 72 pixels per inch; to find out the dimensions on paper, you need to divide the number of pixels that make up the width by 72; height is calculated in the same way.
Width (1200 pixels) divided by 72 pixels per inch is 16.667 inches
Height (800 pixels) divided by 72 pixels per inch is 11.111 inches
So the image size on paper will be 16.667x11.111 inches.
Let's look at the Document Size subsection again:
The sizes are just right! How big will the photo be, right?
Unfortunately, not everything is so 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 a photograph would look like when printed at 72 pixels per inch.
Try to imagine the quality at 11 x 16 inches.
Now the points are too far apart, so there is no sharpness or detail. The quality is muffled, too soft and therefore unattractive. On the screen, everything looks different: monitors are low-resolution devices. Even a relatively small photo, for example, 640x480 pixels, looks great on them. However, printers are high-resolution devices and would require a value much larger than 72 pixels per inch to print well.
How high does the resolution need to be to get professional quality prints? The generally accepted value is 300 pixels per inch; when printed, the pixels are very close to each other, which makes the image look sharp. 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, set 300. Please note that in the Pixel Dimensions subsection, the values \u200b\u200bof 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 number out of 800 pixels of height. With this compression, the photo on paper will be smaller. Therefore, in the Document Size subsection, the photo size is now 4 inches wide by 2.667 inches high.
Let's do the math again:
Width (1200px) divided by 300px per inch - 4 inches
Height (800 pixels) divided by 300 pixels per inch is 2.667 inches
All right!
When printed, the photo will be much smaller than at a resolution of 72 pixels, but much better - we will enjoy a clear and well-detailed image.
Of course, no one will print photos in such non-standard sizes as 4x2.667 inches. How to get a high-quality 4x6 photo? We again have to turn to calculations.
Let's say you've taken some pictures of a family vacation with a digital camera and want to print them in 6x4 size. We now know that in order to achieve professional quality Printing requires a resolution of at least 240 pixels per inch (300 is better).
Let's take a look at both resolution values and decide which is better. At a resolution of 240 pixels/inch, the width and height will be as follows:
240 pixels times 4 inches wide is 960 pixels (width).
240 pixels multiplied by 6 inches in height - 1440 pixels (height).
Total number: 960x1440 - 1382400.
So, the dimension of the photo should be 960x1440. Now most digital cameras have a resolution of 5 megapixels (megapixels or millions of pixels) and higher, so in this case it will not be a problem to print a 4x6 inch photo even at a resolution of 300 pixels / inch. The pixel dimensions will be 1200x1800 respectively (2160000 in total).
But what to do when you need photos 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, its size in pixels should be 1920 pixels wide and 2400 pixels high (or vice versa), and the camera resolution should be about 4.6 million pixels.
A digital camera with a resolution of, for example, 4 megapixels will not provide the required 4.6 megapixels, so it will not be possible to print photos from such a camera with a size of 8x10 at a resolution of 240.
To print an 8x10 inch photo at 300 resolution 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.
Now this is really a large number of points!
To print an 8x10 inch photo at 300 ppi, it must be 2400 pixels wide by 3000 high (or vice versa), total 7.2 million pixels. This is quite a lot, and the camera must be at least 7.2 megapixels! Don't forget that photos sometimes need to be cropped. Therefore, I highly recommend getting an 8MP camera!
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