What is the size of an inch photo (1 authoritative interpretation of the international standard for inch photo size)

In the process of life, study and online work, people often encounter scenes that need to use 1 inch photos, such as qualification examination registration, school registration, job resume, employment permit and so on.

If it is used offline, just find a photo studio for professional photographers to take photos and develop, but it is not so simple online, especially when you register online, you will find many different versions of 1 inch photos, including "large 1 inch", "small 1 inch" and "standard/kloc".

There are many complicated conversion tutorials, which are even more frustrating after reading them:

At the same time, "inch" itself is a very old unit, which is rarely used in real life at present, so "1 inch photo" is only a domestic idiom, and it is more a reference, which cannot directly indicate the size of the photo.

By the way, domestic standards are different from international standards. The domestic standard refers to the diagonal length of a photo in inches. We usually refer to the standard of one-inch and two-inch photos. International standards take the length of the bottom (the longest side) of a photo as the measurement standard, and also take inches as the measurement unit. When we say 3R and 5R, we mean this standard.

In order to simplify the understanding, we describe the traditional "1 inch photo" with modern size calculation units.

According to international standards, 1 inch photos have a width of 25mm and a height of 35mm.

The size of 1 inch photo is 25mm× 35mm, which is basically uncontroversial. The controversy generally lies in the conversion to "pixels", because it also involves the concept of resolution, so when explaining how many pixels 1 inch photos correspond to on the computer, we must first understand what resolution means.

What are the pixels of the photo? A pixel is the smallest independent element (unit) that constitutes a screen image. In actual printing, the concept of pixel is not used, and it is only used in display screens such as computers and tablets. The images we see on the display screen are all arrays of countless single color pixels.

What is the resolution of the photo? The unit of resolution is dpi, which represents the number of pixels accommodated in the 1 inch area. For example, 300dpi= 1 inch contains 300 pixels;

350dpi= 1 inch contains 350 pixels;

96dpi= 1 inch contains 96 pixels;

And one inch = 2.54cm Suppose the picture below is a widescreen computer monitor, and the photo of the big tree displayed above is 300dpi, which means that a square area with a width of 2.54cm× a height of 2.54cm on the monitor contains 300 pixels.

As you can imagine, the more pixels per unit area, the clearer the photo looks. For example, for the same area of 1 inch, the resolution of 300dpi is better than 96dpi. After all, so many extra pixels are not for nothing.

Understanding the concept of resolution, combined with the size of 1 inch photo, can be converted into (1) 1 inch = 2.54cm.

(2) 1 inch photo width 25mm = 2.5 = 0.945 197 inch.

(3) Suppose the resolution is 300dpi and the pixel width of a 1 inch photo is 300× 0.94438+097 = 295.438+0.

(4) Rounding the decimal places, that is, the width of a 300dpi 1 inch photo is 295 pixels, and the English unit is expressed as px (the abbreviation of the word pixel in English).

(5) The process is: mm >；; Cm > inch > pixel

Conclusion: One-inch photos with a resolution of 300dpi have a pixel width of 295px and a high pixel position of 465,438+0.3 px. 300dpi is the most common resolution at present, unless otherwise specified, it is 300 dpi. For example, the above picture is the requirement of China Personnel Examination Network for the registration photos of the qualification examination, and the resolution is not specified, but we can know what it is from the previous calculation formula.

Conclusion: As long as we know the mm/cm size and resolution of the photo, we can convert the pixel size. Unless otherwise specified, it is calculated at 300dpi. Some individuals will ask for 350dpi and 500dpi, such as the registered photos of Shanghai Yousheng Primary School, and you can convert them yourself.

In practical use, you don't have time to switch. I have compiled the following table for your direct reference: all resolutions are 300dpi, and other resolutions can also be converted. Other unusual size conversion relationships, such as small 1 inch, large one inch: if you still feel trouble, directly provide converters and photo automatic production tools: first, turn on your mobile phone and ask an assistant to register for electronic photos. 2. Use self-service to set your own photo specifications or directly select common photo sizes. 3. Selecting the 1 inch photo in the recommended scheme will automatically bring out the resolution, pixels and so on. In addition, you can also set the photo K size and photo background color in one step (intelligently change the photo background color).

Fourth, other strange specifications can be converted back, that is, the converter can support the conversion between pixels, size and resolution:

Fifth, upload a half-length bareheaded photo. Sixth, click Preview. Is it convenient to take a standard inch photo? Collect it quickly, and you will be an expert in making ID photos in the future.