Concepts about pixels and resolution

These are basic concepts, but the more basic the concept is, the more general it is, the less common this concept is in normal work, but sometimes I can't make it clear when I think of it or when someone asks.
I searched the information on the Internet and it seems to be a little more detailed.
1. What is pixel?

To put it simply, what we usually call pixels is the number of photoelectric sensing elements on CCD/CMOS. After a photosensitive element passes through photosensitive, photoelectric signal conversion, A/D conversion, and other steps, A point is formed in the output photo. If we enlarge the image several times, we will find that these consecutive tones are actually composed of many small vertices with similar colors, these vertices are the smallest unit of pixels that constitute an image ).
Pixels are divided into CCD pixels and valid pixels. Currently, most of the digital cameras on the market mark CCD pixels rather than valid pixels.

2. What is resolution?

Speaking of pixels, we have to talk about the resolution. Because they are inseparable!

The so-called "resolution" refers to the number of pixels expressed or retrieved per unit length. Like pixels, resolution can be divided into many types.

The most common one is the image resolution. The maximum resolution of a digital camera output photo is the image resolution, in the unit of pixel per inch)

Print resolution is also a common one. As the name suggests, it is the output resolution of a printer or printing device, in DPI (DOT per inch)

Display resolution is the size of the Windows desktop. Common settings include 640x480, 800x600, 1024x768... . Screen font resolution: the PC font resolution is 96 DPI, and the Mac font resolution is 72 dpi.
Of course there will be resolutions of other output devices. As there are many types of data, we will not detail them here. If you are interested, you can search for them online.

3. Relationship between image resolution and pixels

Let's take a look at the relationship between pixels and resolutions. Careful friends may have discovered that pixels are directly proportional to the resolution. The larger the pixel, the higher the resolution. Let's give an example!

As mentioned above, pixels are divided into valid pixels and CCD pixels.

Generally, for a 2 million-pixel digital camera, the maximum image resolution is 1600 × 1200 = 1.92 million pixels, that is, the actual valid pixel is 1.92 million.

Generally, for a 3 million-pixel digital camera, the maximum image resolution is 2048 × 1536 = 3145728 pixels, that is, the valid pixel is 3.14 million.

The resolution and effective pixel conversion of other pixel-level digital cameras are also the same.

The higher the pixel, the higher the resolution of the maximum output image.

4. Relationship between print resolution and pixels

The print resolution is related to the size of the printed photo, so it is also important.

In fact, the calculation method is also very simple:

2 million pixel digital camera, valid pixel 1.92 million, maximum output of 1600x1200 photos

Width: 1600 pixels/300 dpi = 5.3 ″

Height: 1200 pixels/300 dpi = 4 ″

That is to say, if a 5.3 DPI output resolution is used for printing, a maximum of 4 inch × photos can be printed. The general size of the photo is:

5 inches: 5x3.5
6-inch: 6x4

Obviously, 2 million pixels can print up to 5-inch photos with a DPI effect.

(Note: The maximum resolution that can be distinguished by human eyes is 300 dpi. Beyond this resolution, human eyes cannot see the difference. That is to say, there is no difference between DPI and DPI, therefore, the maximum design output resolution of the current printing equipment is 300 dpi. Of course, the definition requirements are different for everyone. Generally, DPI can satisfy most people, therefore, the printing of 6-inch photos with 2 million pixels is clear to most people .)

Conclusion: As mentioned above, the "Print size" has a great relationship with the image resolution. As long as the image resolution changes, the print size will change, pixel and image resolution are directly related, so the three can be converted to each other. The most fundamental is pixel.