Photo resolution. Pixels, Megapixels, Image Resolution, and Digital Photo Print Sizes

Many of us love to take pictures. The variety and availability of digital cameras make photography a popular pleasure to capture the bright, colorful moments of our lives. At the same time, the high quality of the resulting photographs does not guarantee the same quality when printing digital images on standard roll photo paper. In this material, I will tell you what sizes of photos for printing are, 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

In order to understand what are the sizes of photographs for printing and what are their specifics, we need, first of all, to understand the basic concepts necessary to understand the process of digital printing.

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.

Sometimes it happens that you need to resize an image. The reason for this can be many factors. Firstly, the higher the resolution of the photo, the larger its size, and such files can be problematic to store on the device. Secondly, if you need to upload a photo via the Internet, problems may arise, because some file hosting services have a maximum allowable photo size limit.

That is why in the article we will talk about how to change the resolution of a photo. This may come in handy when working at a computer, so let's get started.

What is permission

First of all, let's understand what permission is. And the term is basically simple: resolution is the number of pixels vertically and horizontally in an image.

As you know, the more photos have the same pixels, the larger its size. However, in our time there are innumerable programs that can reduce the image, thereby reducing its size and without losing quality. Well, now let's talk more about how to change the resolution of a photo.

I would also like to say that if the number of pixels is reduced relative to the original value, the photo will not lose quality, but if the same value is increased, the difference will become noticeable.

Method number 1. Paint

Probably everyone is familiar with the Paint program. But despite its small number of functions, it is able to help in changing the resolution of a photo.

So, let's say you have a photo with a resolution of 3,000 by 4,000, and you want to reduce this number by half. To do this, open Paint. You can use the search by calling it using the Win + Q keys. There, immediately click on "File" and select "Open". In the explorer that appears, specify the path to the desired photo and click "Open".

You now have your photo in front of you. To change its resolution, click "Resize". This button is located on the top panel next to "Select".

Now a small window has opened, in which, first of all, you need to choose in what quantities the size will be changed. There are two options to choose from: pixels and percentages. We choose the first. Now you need to check the “Keep aspect ratio” checkbox, this will prevent the photo from shrinking or flattening.

Now you can start resizing. Since we initially wanted to reduce the photo by half, we enter the value 2000 in the “Horizontal” field. You probably noticed that the “Vertical” field filled in by itself, this is due to the fact that the “Keep proportions” checkbox is checked ".

Now click OK and we can safely save the photo in the new size: "File - Save".

This was the first way to change the resolution of a photo - in Paint, now let's move on to the second.

Method number 2. Adobe Photoshop

Now let's move from small to large, more precisely from Paint to PhotoShop. Of course, these are two, but they are nothing alike, but this approach will not be fundamentally different from the previous one.

So, we begin to figure out how to change the resolution of a photo in Photoshop. First you need to open it. Right after that, click "File" and then "Open" and navigate to your photo.

Now click on the same toolbar item "Image". In the list, select the line "Image size ...". Or you can just press Alt + Ctrl + I.

In the window that appears, immediately check the box next to "Keep proportions." And in the "Dimension" column, select "Pixels" in the drop-down list. Now feel free to resize the photo.

Now you know how to change the resolution of a photo without losing quality using PhotoShop.

Conclusion

As you can see, you don't need to know much to change a photo. Everyone can perform the above manipulations, and in the end you will get what you want: the photo will change, but the quality will remain the same, and the file size will noticeably decrease. We hope this article has given you the answer to your question about how to change the resolution of a photo.

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?
Should I post high-resolution photos on 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 taken with a digital SLR 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 settle for 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, " there is no new information in these pixels. 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 different 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. The Epson Photo family of printers are very popular, 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.

The Easy Way To Good Photos

We present to your attention our selection of the largest photographs in the world. You will need FlashPlayer to view them. You can download it separately or use the Google Chrome browser.

Photopanorama of the Moon - 681 Gpc.

The absolute champion in the size of composite photos is NASA. In 2014, the agency released a 681 gigapixel panorama of the moon. On June 18, 2009, NASA launched the Lunar Reconnaissance Orbiter (LRO) to map the lunar surface and collect measurements of potential future landing sites, as well as for scientific purposes.

You can view the panorama on the website.

Photo panorama of Mont Blanc - 365 Gpc.

At the end of 2014, an international team of professional photographers led by Filippo Blegnini made a circular panorama of the mountain range between France and Italy - Mont Blanc, the second highest mountain in Europe after Elbrus.

It consists of 70 thousand photos! Photos taken on a Canon EOS 70D with a Canon EF 400mm f/2.8 II IS telephoto lens and a Canon Extender 2X III. The creators of the giant panorama claim that if printed on paper, it would be the size of a football field. To date, this is the largest gigapixel photograph taken on earth.

You can view the panorama on the project website.

Photo panorama of London - 320 Gpc.

The panorama was compiled from 48,640 individual images taken with four Canon 7D cameras and posted online in February 2013. Preparation for the experiment took several months, and the shooting took place over four days. The pictures were taken by British Telecom from the top of the BT Tower in central London on the north bank of the Thames. Photographed by 360cities.net panorama experts Jeffrey Martin, Holger Schulze and Tom Mills.

You can view the panorama on the website.

Photo panorama of Rio de Janeiro - 152.4 Gpc.

The panorama was taken on July 20, 2010 and consists of 12,238 photographs. Uploading the final image to gigapan.org took the author almost three months!

You can view the panorama on the website.

Photo panorama of Tokyo - 150Gpc.Fo

The panorama was created by Jeffrey Martin, founder of 360cities.net. The panorama was created from 10,000 different images taken from the observation deck of the Tokyo Tower television tower. When creating it, the photographer used a Canon EOS 7D DSLR and a Clauss Rodeon robotic car. It took two days to get 10 thousand frames, and three months to bring them into one panorama.

You can view the panorama on the website.

Photo panorama of the national park "Arki" - 77.9 Gpc.

The author of the panorama is Alfred Zhao. Arches is a national park located in the US state of Utah. There are more than two thousand arches formed by nature from sandstone. It took 10 days of processing, 6 TB of free hard disk space, and two days of uploading the final image to the site to create the panorama. The photo was taken in September 2010.

You can view the panorama on the website.

Photo panorama of Budapest - 70 Gpc.

In 2010, a team of enthusiasts sponsored by Epson, Microsoft and Sony created what was then the largest 360-degree panoramic photo in the world. The project was called "70 billion pixels of Budapest". The 70-gigapixel photo was taken four days from the city's 100-year-old observation tower. The panorama was more than 590 thousand pixels wide and 121 thousand pixels high, and the total number of shots was about 20 thousand. Unfortunately, the link doesn't work right now.

Photo panorama on Mount Corcovado - 67 Gpc.

This photo was taken on Mount Corcovado in Rio de Janeiro (Brazil), where the statue of Christ the Redeemer is located. The photo panorama was made in July 2010 and was created from 6223 frames.

You can view the panorama on the website.

Photo panorama of Vienna - 50 Gpc.

A gigapixel photo panorama of Vienna, the capital of Austria, was created in the summer of 2010. It took 3600 shots to make it, but the result was worth it.

You can view the panorama on the website.

Photo panorama of Marburg - 47 Gpc.

Marburg is a university town with a population of about 78,000. The panorama took 5,000 shots, which were taken with a Nikon D300 camera with a Sigma 50-500 mm lens from a tower 36 meters high. Each of the photographs has a size of 12.3 megapixels. It took the author 3 hours and 27 minutes to shoot, and the total amount of information he received took up 53.8 GB of hard disk space.

You can view the panorama on the website.

Milky Way - 46 Gpc.

For five years, a group of astronomers from the Ruhr University, using an observatory located in the Chilean Atacama Desert, followed our galaxy and created a giant photograph of 46 billion pixels from images of the Milky Way. The image weighs 194 GB.

You can view the panorama on the website.

Photo panorama of Dubai - 44.8 Gpc.

The author of the panorama is Gerald Donovan. Dubai is the largest city in the United Arab Emirates. A Canon 7D camera with a 100–400 mm lens was used to create the panorama. The author worked for more than three hours in 37-degree heat and took 4250 photographs.

You can view the panorama on the website.

Photo panorama of the backyard - 43.9 Gpc.

The 4048 panorama photos were taken on August 22, 2010 in the village of Round Lake, Illinois, USA. The author, Alfred Zhao, used a Canon 7D camera with a 400 mm lens. The shooting took two hours, but the processing of photos took about a week.

You can view the panorama on the website.

Photo panorama of Paris - 26 Gpc.

The author of the panorama is Martin Loyer. At the end of 2009, the interactive site www.paris-26-gigapixels.com appeared on the Internet, which has a huge gigapixel photo panorama of Paris with very clear resolution, consisting of 2346 photos. It will allow you to immerse yourself in the image of this city and see its sights without leaving the house.

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 size 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.

The documents

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.

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All the best to you, Timur Mustaev.