Technical requirements for digital printing

How to calculate the correct image size and resolution for printing and displaying on the screen

One of the most confusing things for a new photographer can be understanding the difference between file size and resolution for printing or displaying on a monitor. In this article, photographer Helen Bradly helps you figure it out and shows you how to resize images depending on what you want to do with them: print or display on the screen of an electronic device
. Let’s start.

What is the resolution of digital cameras?

When it comes to digital cameras, resolution refers to the number of megapixels produced by the image sensor. This in turn usually corresponds to the amount of detail the camera can capture. So if your camera has 20 megapixels (often referred to as 20 MP), it will capture less detail than a 30 megapixel camera, which in turn will capture less detail than a 40 megapixel camera. But what is a megapixel, really? ? And how does this affect your ability to print and display photos?

Megapixels and photo size

Как рассчитать правильно размер и разрешение изображения для печати и отображения на экране

Technically, a megapixel is equal to 1,048,576 pixels; in fact, camera manufacturers round this number to the nearest 1,000,000 when talking about what image size the camera will capture.

Helen’s camera, for example, captures 14.6 megapixel images, which is about 14,600,000 pixels per image (14.6×1,000,000). This information doesn’t tell you anything about the actual pixel dimensions of the image, it only tells you the total number of pixels that make up the image.

Its camera, like most DSLRs, shoots images with an aspect ratio of 1.5. Thus, the ratio of the number of pixels along the long edge of the image to the short edge of the image is 3:2.

Each of the full-size RAW images
photographer has a size of 4672×3104 pixels. So, by multiplying the number of pixels in the width of the image by the number of pixels in the height of the image, we get the actual number of pixels in the image (4672×3104 = 14,501,888). We could call it 14.5 MP, but camera manufacturers have rounded up the number and call such a camera 14.6 MP.

You can check the width and height of the image using photo editing software. In Photoshop, you can open an image, then choose File > File Info > Camera Data. The image above shows the dialog box with the information received.

So, a pixel itself is a single element of an image – and for our purposes, it is the smallest element into which a photograph can be divided. A pixel can only be one color, but a photograph is made up of a grid of thousands of pixels, each with a different color, that together make up the final image. You can see the pixels if you open the photo and zoom in until you see individual blocks of color (as shown below). Each of these blocks represents a separate pixel.

Как рассчитать правильно размер и разрешение изображения для печати и отображения на экране

Why size is important when printing

When printing images, photographers come across the term PPI/DPI or pixels per inch. D PI refers to the number of dots contained in one inch of an image printed on paper by a printer. P PI refers to the number of pixels contained in one inch of image displayed on a computer monitor. Most printing services and your own printer will require a certain pixel density in the image (PPI) to be able to print a photo that looks good (that is, with smooth color transitions so you don’t have to look at every single pixel).

Typical print PPI values ​​range from 150 to 300 PPI, although some high-quality magazines may require 1200 PPI images. So, for example, if you want to print a 4×6-inch image at 300 pixels per inch, you’ll need a file that is at least 4×300 (1200) pixels on the short side and 6×300 (1800) pixels on the long side. In other words, it must be at least 1200×1800 pixels in size.

To print an 8×10 inch image at 300 PPI, use the same math.

Multiply the width and height of the printed image in inches by 300 pixels. The result is 2400×3000 pixels, which is the image resolution needed to print an 8×10 image at 300 pixels per inch. So when cropping and resizing an image for printing, you need to know what the PPI of the image should be. This should be stated in your printer manual or printing service.

Below is a screenshot from the MpixPro.com website showing the optimal and minimum image sizes for standard print sizes. The printer prints them
at 250 PPI (but can handle 100 PPI images), although other services may vary, so always check before preparing images for printing.

Use the crop or resize function in your software to resize the image to the desired width and height and desired PPI resolution.

Here, an image cropped to 3000×2400 pixels is adjusted from 72 PPI to 300 PPI in preparation for printing at 300 PPI. No resampling is required since the image is already at the correct dimensions and only resolution is required.

Как рассчитать правильно размер и разрешение изображения для печати и отображения на экране

Photoshop, like other applications, will also crop an image to a fixed size and resolution if you enter the desired values ​​in the Options Bar when you have the Crop Tool selected (see below). If your image is smaller than the specified dimensions, it will be enlarged using the default resampling method. While it is generally not recommended to enlarge images, provided the image is already close to the desired size, enlarging it slightly usually does not cause a noticeable loss in quality.

Как рассчитать правильно размер и разрешение изображения для печати и отображения на экране

Fit to screen

When it comes to displaying images on screen, you need far fewer pixels than when printing. This is because the pixel density on the screen is much less than what is required for printing. For example, the size of a regular FullHD monitor is 1920×1080 pixels. To fill your monitor, you only need a 1920×1080 pixel image. This is about the same image size needed for a 4×6 print at 300 PPI, but still displays a 1920×1080 pixel image perfectly on a 23-inch monitor.

What points are important to consider when choosing a printing device:

  1. Don’t go for cheap prices.
    Nowadays you can find printers and multifunction devices in stores that cost even up to 4,000 rubles. The problem with such printers is that the cartridge really only lasts for a maximum of 100 sheets. Manufacturers of such devices sell you a printer for next to nothing
    , in order to “get you hooked” on expensive cartridges in the future
    , each of which costs about 1,500 rubles (1 black and 1 color cartridge are required for printing). Roughly speaking, you get a printer almost free of charge, but you pay the manufacturer a monthly amount of about 3,000 rubles.
  2. We recommend choosing a printer with continuous ink supply system
    (CISS). This system consists of containers with ink instead of cartridges, connected to the print head of the printer. The benefit of this approach: less ink is consumed, less need to be refilled; It’s easier to refill ink – just pour the paint into the container; You can use budget ink from a third-party manufacturer – but this is at your responsibility, since low-quality ink can affect both the quality of the pictures and the technical condition of the printer.
  3. How to print photos from your phone? Take a closer look at compact sublimation photo printers
    . Today on the market there are models such as, for example, Canon Selphy. This printer is intended only for printing digital photographs in 10×15 format, but is characterized by very high ease of use. Canon Selphy - компактный сублимационный фотопринтер
  • You can take it with you to nature
  • Print from your phone (although this function is already available on many modern models)
  • Very compact and easy to use.

Review of popular photo formats for printing

There are generally accepted international ISO formats that define standard sizes for photographic paper. However, terms such as A3, A4, Whatman paper, etc. have become more familiar to us. The aspect ratio of the main photo formats is similar to the matrices of modern digital cameras and is 1: 1.5 (2/3) or 1: 1.33 (3/4), and standard international paper sizes are 1: 1.4142.

We invite you to familiarize yourself with the table, which shows the main photo formats for printing.

Let’s take a closer look at the main options and compare them with standard ISO formats.

Соотношение формата A4 и фото 10х15

One of the most popular photo formats for printing is 10×15. It differs from the standard A6 in that it is 2 mm smaller on one side and 5 mm larger on the other. This is perhaps the most common format and is suitable for almost all photo albums and frames. The photo shows how the 10×15 image compares to A4 photo paper.

Соотношение формата A4 и фото 15х21

An equally popular photo size for printing is 15×21. The photo is slightly larger than A5. The difference is very small: on one side the difference is 5 mm, on the other – 1 mm. Vertical photographs are ideal for creating portraits.

Соотношение формата A4 и фото 20х30

The photo format for printing 20×30 is close to A4, the difference is that on one side the image is 6 mm smaller, on the other – 9 mm larger. The peculiarity of photographs of this size is high detail and clarity. That is why images are often used to create posters, which are an excellent interior decoration.

Соотношение формата A3 и фото 30х40

Using a 30×40 photo for printing is an excellent option for creating a highly artistic wall composition. The difference between the format and A3 is that on one side and the other the image is larger by 9 mm and 1 mm, respectively. Photographs are often placed in a wooden frame or stretched on a stretcher.

Соотношение формата A3 и фото 30х45

Photo format for printing 30×45 is one of the favorites among users of the Mimigram application. This size is ideal for making posters
. The printed images are incredibly clear and colorful. That is why posters are often used to organize photo exhibitions. The format is slightly larger than standard A3.

Print Quality Chart

Resolution Mpx Size
9×13 10×15 13×18 15×20 20×30 30×40
640×480 0.3 Very bad Very bad Very bad Very bad Very bad Very bad
1280×1024 1.3 Good Normal Poor Poor Very bad Very bad
2048×1536 3.1 Excellent Excellent Good Good Poor Very bad
2304×1729 4.0 Excellent Excellent Excellent Good Normal Very bad
2592×1944 5.0 Excellent Excellent Excellent Excellent Normal Poor
3000×2000 6.0 Excellent Excellent Excellent Excellent Good Bad
3200×2200 7.0 Excellent Excellent Excellent Excellent Good Normal
3600×2300 8.3 Excellent Excellent Excellent Excellent Good Good
  • Photo printing
  • T-shirt printing
  • Print on cup
  • Photo puzzle
  • Large format printing

Photo printing sizes and formats

Our professional equipment makes it possible to process and edit files only with the JPG extension; other formats are not accepted. In order for the image in the photo to be contrasty and clear, the resolution must vary from 72 to 300 dpi, in other words, the quality of the print depends on the number of dots per inch.

The size of the photo matters; sometimes a minimum number of pixels is enough, but for large-format printing of large sizes (a1, a2, a3) the optimal number is required. The sizes and formats of photo printing do not always correspond to the frame format in a digital camera, therefore, in order to avoid cropping the main elements of the overall plot, you should take into account the aspect ratios.

When placing an order, the print operator pre-reviews the image and, if necessary, crops it manually. For the convenience of consumers, on our website the sizes and formats for printing photographs are presented in table form. The standard format is a clearly defined linear dimension.

In one order, you can choose a completely different print format for each photo.

The color rendition of the client’s monitor and our equipment may differ significantly, so it is better to entrust color correction to professionals or order a test print to adjust the balance of brightness and color.