What does12 million pixels mean?

Pixel is the smallest unit of a picture, and it is monochrome. Pictures are made up of such rows of small things of different colors.

120,000 pixels is the unit of120,000. There are about 4000 in a row and about 3000 in a column. If all are counted, it is about 6.5438+0.2 million.

12 million is an approximate number, which may not be completely12 million.

12 megapixel picture file, there is no problem in developing 20-inch photos.

What does pixel mean? How big is a pixel? Tell you the relationship between pixels and resolution!

Text/Liu Fu Luo Jin 20 1209 12

Pixel and resolution of the picture

The words pixel and resolution mainly appear in pictures and display devices. As long as you use the camera function in your mobile phone, you have to touch these two concepts. It's just that most people have a little knowledge, and more people don't know at all. The 5 million and 8 million pixel cameras wasted in mobile phones don't know how to adjust and use them.

A pixel is the most basic unit element of an image: a point. Resolution refers to the number of pixels in both length and width directions. How big is a pixel? Mainly depends on the resolution of the display, the pixel size of the display screen with the same area and different resolutions is different.

As we all know, lines are made up of countless points, while surfaces are made up of countless lines, that is, a plane is made up of countless points. However, no matter how advanced and developed the technology is, it is always impossible for human beings to make an image consist of countless points, only a limited number of points in the length and width direction.

These limited points are called pixels, and the number of pixels in each length direction is well represented by the number of pixels in each width direction, which is called the resolution of the picture.

For example, a picture of 640X480 means that the picture has 640 pixels in each length direction and 480 pixels in each width direction, with a total of 640X480=307200 (pixels), or 300,000 pixels for short.

Obviously, the more pixels per unit area, the smaller the pixels, and the clearer and more delicate the picture will be. So how big is this pixel? It is impossible to determine how big this point is simply from the picture. This size is closely related to the resolution of the display screen.

Resolution of display screen

The size of the display screen refers to the length of its diagonal, expressed in inches, 1 inch =25.4 mm.

Let's take a mobile phone as an example to illustrate this problem. Its main screen size is 4 inches and its resolution is 800x480 pixels. According to Pythagorean theorem, its length and width are 3.430 inches X2.058 inches (87. 1mm x 52.3mm). 800/3.430=233, that is, there are 233 pixels per inch, and the size of each pixel is 87. 1/800=0. 109 mm.

That is to say, the display of this mobile phone * * * is composed of 800X480=384000 pixels, with a side length of 0. 109mm and the same size. When any picture is displayed in full screen on this monitor (the picture is best protected as wallpaper or screen), its pixels are so large. If the picture is larger than the display screen, you must slide the scroll bar to see the complete picture. If it is smaller than the display screen, it will be displayed in the center, and the places without pictures will be displayed in black boxes. For graphics with a resolution of 640X480, it will be displayed in the center of the display screen, and the parts at both ends in the length direction will be displayed as black boxes. The size of this picture is 69.68 mm long and 52.3 mm wide. If the photo is taken in poor light, you will see a mosaic of squares, and the picture is very rough.

For the 4.3-inch main screen, if the resolution is 1280x720 pixels, the length and width are 3.746x2.108 (95.2mm x 53.5mm), 1280/3.746=34 1, that is, the length of each inch is. Obviously, this screen is much better than the last one. Here, the length and width of the 640X480 resolution picture are 47.6 mm and 35.7 mm respectively.

For a 4.5-inch home screen, if the resolution is 1280x720 pixels, the length and width are 3.923X2.206(99.6 mm X56.0 mm), and 1280/3.923=326, that is, there are 326 pixels per inch, and each pixel has 99.6/656. Similar to the front 4.3-inch screen.

17 inch LCD (5: 4) with resolution of 1280X 1024 and 96 pixels per inch; Each side is 0.263 mm long.

19 inch flat panel display (5: 4), its resolution: 1280X 1024, 86 pixels per inch; Each side is 0.294 mm long.

19-inch widescreen display (16: 9) with a resolution of 1366X768 and 82 pixels per inch; Each side is 0.308 mm long.

19-inch widescreen display (16: 10) with a resolution of 1440X900 and 89 pixels per inch; Each side is 0.284 mm long.

This digital PPI is called image resolution, or PPI for short. If there are 82 pixels per inch of length, it is represented by 82PPI.

Therefore, the size of the same picture on different PPI (image resolution) display screens is different, and the size of pixel points is related to the image resolution.

The size of the photo in the camera

The camera is the same as our monocular. Of course, monocular left and right 160 degree field of vision, up and down 120 degree field of vision. However, it is difficult for the largest ultra-wide-angle digital camera to reach this range. It is said that the viewing angle range of fisheye lens camera can reach 220 to 230 degrees. But no matter how big the viewing angle is, the ratio in the left-right length and the up-and-down width direction is the same as that of the human eye, that is, 160: 120 = 4: 3. Therefore, the size of the picture is also the majority of this ratio, such as:

150000 pixels 480X320= 153600

200,000 pixels 640X320=204800

300,000 pixels 640X480=307200

500,000 pixels 800X600=480000

800,000 pixels 1024X768=786432

1 megapixel1140x900 =1026000

65438+300,000 pixels 1280X960= 1228800

2 million pixels1600x1200 =1920000.

3 million pixels 2048x1536 = 3145728

5 million pixels 2576X 1932=4976832 or 2592X 1944=5038848, 2560x1920 = 4915200.

8 million pixels 3264X2448=7990272

100000 pixels 3648X2736=9980928

12 million pixels 4000X3000= 12000000.

1400,000,000, full line 4228 x 3264 =13800192.

And 16: 9, for example

9 million pixels 4000X2256=9024000

There's even 3: 2! such as

6 million pixels 3000X2000=6000000

1 1 Megapixel 4000X2664= 10656000

There are also 5: 4, such as

1.3 million pixels1280x1024 =1310720.

Of course, there is the golden section coefficient, namely16:10 =1.6:1=1:0.618, as shown in the following figure.

1 megapixel 1280X800=960000

At present, most of the cameras of mobile phones are 5 million pixels and 8 million pixels, and a few are12 million pixels. The highest pixel is Nokia's new smartphone 808, which has reached an unprecedented 4/kloc-0.0 million pixels, 7728X5368=4 1483904 pixels. The online quotation is less than 4000 yuan, but this pixel-level digital camera costs 65438+ 10,000 yuan! The 60-megapixel Hasselblad SLR H4D60 costs more than 200,000 yuan.

Our human eye is a super digital camera, and every cell on the retina is a photosensitive cell, which is a pixel. So how many pixels do people have in their eyes? According to research, there are 576 million. I heard that someone built 10.

Megapixel cameras are only used for astronomical research or military applications, and individuals can't afford them. Maybe it will be widely used in the near future.

Obviously, the aspect ratio of the display screen should also be done according to this. The best resolution of general display screen is as follows: 15 "flat LCD (1024× 768)-4: 3.

17 inch flat panel LCD (1280× 1024)-5: 4

19 inch flat panel LCD (1280× 1024)-5: 4

19 inch widescreen LCD (1440× 900)-16:10.

20-inch flat panel LCD (1600×1200) (1400 *1050)-4: 3

20-inch widescreen LCD (1680×1050) ——16:10.

2 1 inch flat panel LCD (1600× 1200)-4: 3

22-inch widescreen LCD (1680×1050)-16:10.

23-inch flat panel LCD (1600× 1200)-4: 3

23-inch widescreen LCD (1920×1200)-16:10.

24-inch widescreen LCD (1920×1200)-16:10

Can you see the Great Wall from space?

Some people may ask, how thin can our eyes at least see?

According to relevant research data, human eyes can see at least 0.02 to 0.0 1 mm thick dots. That is 1270 to 2540PPI.

Someone once swore that "the Great Wall is the only man-made building that can be seen in space". Can you believe it? Can you see the Great Wall from space? According to the principle of being near and far and small, how big is the Great Wall seen from space?

Children are often taught that when reading, books should be one foot away from their eyes. It can be seen that the best distance for people to see things is about 33 cm away from them. Being too close will not only make you see more clearly, but will blur your vision. If you get too close, you will be nearsighted.

Let's assume that there is a very awesome astronaut who can see a dot with a thickness of 0.0 1 mm 50 cm away. So how wide is the Great Wall? It is said that the narrowest part is 2 meters, and the widest beacon tower is 8-9 meters wide. Suppose it is 10 meter wide everywhere! Suppose the weather is fine, especially fresh, and there are no clouds in Wan Li.

Then it is 0.5x (10.00001) = 500,000m = 500km, which means that the Great Wall seen by our astronauts at an altitude of 500km is only 0.0 1 mm thick. The spacecraft is generally about 340 kilometers away from the earth's surface, so let's take it as 340 kilometers. What does the Great Wall look like at this height?

1.8x (340/10) =1.8x34 = 61.2 (km), that is to say, you are looking at a place 6 1.2 km away.

1.8 meter high wall.

10x (10/350000) = 0.0002857143 (m) = 0.3 (mm), and the size of a sesame is 1mm, so consider it a red cloth belt with a width of 0.3mm! Seeing the Great Wall at an altitude of 350 kilometers is equivalent to seeing a red cloth belt with a width of 0.3 mm at a distance of 10 meter.

If you still don't understand, then use hair as an analogy!

Our hair is about 0.05 mm thick. In the case of sufficient light and excellent eyesight, and the background where the hair is placed is white. You should be able to see your hair 2 meters away. Can you see it from 5 meters away? Suppose it's just visible! Or suppose that the Great Wall is 10 meters wide everywhere!

Then 5x (10/0.00005) = 1 10,000 meters = 1000 kilometers, which means that the Great Wall seen at a distance of 1000 kilometers is like a hairline. For spacecraft flying over 340 kilometers, the Great Wall that astronauts can see is 0.00005 (340000/10) = 1.7, which is equivalent to looking at a hair at a distance of1.7 meters. 1(340/ 10)=34 (km), that is, it is the same as looking at a child 1 meter high from 34 kilometers away. Do you think it is possible to see it?

Therefore, it is impossible to see the Great Wall in the sky. It's no problem to see the Great Wall on the plane.

What else is in the pixel?

Images composed of pixels are called bitmap or raster images, bitmap, pixel map and grid map. The word grating comes from analog TV technology, and our TV signal is analog. )。

Generally speaking, a pixel is a square with color letters such as height, hue, hue, color temperature and gray level.

Information, a certain number of colors have other small squares arranged and combined to represent a dot matrix image, that is, a bitmap image. Images taken by digital cameras, scanned by scanners or output by bitmap software are all bitmaps.

The richer the color information of the bitmap, the greater the capacity of the picture. Photographs obtained in a well-lit environment usually have a large capacity. My12 megapixel picture, minimum 2.2M bytes, maximum 6M bytes.

The research shows that when it exceeds 300ppi (the pixel point is 0.085 mm), the human eye cannot perceive the graininess. If all the photos we took are 100%, you must find that they are all mosaics, which is terrible!

When the resolution of the picture is greater than that of the display screen, the display screen will reduce the picture proportionally. This is equivalent to displaying two or more pixels of a picture as one pixel on the display screen. Therefore, the greater the resolution of our pictures, the clearer, more delicate and more lifelike the pictures we see. So when we take pictures, we must take pictures with the maximum resolution. The images printed by digital printing shops are also clearer than those with low pixels! The resolution is too low, sometimes it can't be used as wallpaper.

Relationship between pixel value and final print photo size

People often ask: My picture is 2048X 1536, can I take a 5-inch photo? My camera is 500W pixels. How many inches of photos can I print at most? This question is simple and simple, not simple and not simple. We only need to care about three indicators:

Number of pixels, printing accuracy, frame size.

Because the picture on the camera is in 4:3 mode (or 3:2, 16: 9, 16: 10. ), but the border of the photo is not necessarily: there are 3:2, 4:3, 5:3.5 and so on.

Usually "inch" is used to represent the specifications of photos, which is different from the diagonal length of products such as monitors. "A few inches" in a photo refers to the length of one side of the photo in the length direction, and is generally rounded to the nearest integer. For example, the size of a 1 inch photo is 1X 1.4, which is expressed by the size of the long side of 1.4, that is 1 inch; The 5-inch phase specification is 5X3.5, and the long-side dimension 5 is used to indicate the specifications of its photos.

There is also a commonly used method to indicate the size of a photo in the world, which is to take the integer value of the short side of the photo and add the letter R to indicate it. For example, a 5-inch photo with a specification of 5X3.5 inches is 3R; 6-inch photo, the specification is 6×4 inches, that is, 4R.

Printing accuracy is the number of pixels printed by the printer per inch in the length direction, which is generally based on 300dpi. 120dpi is the minimum requirement and 150dpi is the lower limit of safety compliance. Generally speaking, 250dpi is enough. Therefore, 250dpi is generally used to calculate the minimum resolution of the pictures needed for printing photos.

2048/5=409.6, which obviously meets the requirements! 300W pixels, the lens length is generally 2048,2048/300 = 6.83 inches. It is known that the printing is 7 inches, no problem! Of course, if you print a 7-inch photo, the picture is 1280X960 pixels, which is equivalent to enlarging the picture on the display screen, although it is not clear.

Like 8 million pixels, 3264X2448, 3264/300= 10, printing a photo of 10 inch is just right, but 100% is displayed, so you can imagine how ugly its definition is. Unless it was taken in a very good environment. But if you print a 7-inch photo, the machine will naturally adjust the parameters to reduce the image accordingly, so that the printed photo will be much clearer.

Black and white photos have become history. Color photos are just the time to run wild. Maybe in the near future, it will be stereo photo's world.

Now the residence permit and other documents are 1 inch photos. Its size is 1X 1.5(25mm×35mm).

If calculated at 300dpi, 5X300= 1500, a picture with10 million pixels140x900 =1026000 can't print a 5-inch photo. It must be 2 million pixels1600x1200 =1920000. Even if it reaches 250dpi (5X250= 1250), it still won't work. Must be 1.3 million pixels 1280X960= 1228800.

Shooting resolution ÷ 300 dpi = output size (best)

Shooting resolution ÷ 250 dpi = output size (generally required, the following minimum resolution is calculated. )

Normal photo size photo specifications (inches) (millimeters) (minimum resolution of 250dpi is required)

1, 1 inch 1X 1.5 25mm×35mm color photos, residence permit, brand name, application form and other files and small documents such as student ID cards are used more;

Small 1 inch black and white small one inch 22mmX32mm (it seems to have been eliminated, and many materials on the Internet have been copied and pasted incorrectly. ) ;

Driving license color one inch 22mm x 32mm

Color is one inch smaller, 27mmx38mm.

The second-generation ID card is 26mm x 32mm；;

One inch 33mmX48mm passport (including Hong Kong and Macao passes), travel documents, graduation certificates and other documents.

1 inch 26 mm x 37 mm.

2, 2 inches1.5x2 35mm x49mm; ;

Small 2 inch 35mm x 45mm；;

Sophomore, 35 mm x 53 mm

2R (2 inches) 63mm× 89mm.

3. 5-inch (3r) 5x3.5127mmx89mm1280x960 (1.3 million pixels), 1280x800 (1 million pixels),/kloc-0. This is our most commonly used photo.

4.6 inches (4r) 6x152mmx102mm1600x1200 (2 million pixels).

5, 7 inch (5R) 7x5178mmx127mm2048x1536 (3 million pixels).

6. 8-inch (6r) 8x6203mmx152mm 2048x1536 (3 million pixels).

7. 10 inch (8r)10x8 254mmx203.2mm 2576x1932,2592x1944,2560x1920 (5 million pixels) 8. 12 inch12x/kloc-0 304.8mm x 254mm 3000x2000 (6 million pixels) and 3264x2448 (8 million pixels). 9. 14 inch14x12 355.6mmx304.8mm 3648x2736 (100000 pixels).

10, 16 inch12x16304.8mm x 406.4mm 4000x2256 (9 million pixels), 4000x2664 (11million).

1 1, 18 inch 14x 18 355.6 mm x 457.2 mm (omitted).

12, 18 inch12x18304.8mmx457.2mm (omitted).

13,20 inch 16X20 406.4mmX508mm (omitted).

14,20 inch 18X20 457.2mmX508mm (omitted).

15,24 inch 20X24 508mmX609.6mm (omitted).

16,30 inch 24X30 609.6mmX762mm (omitted).

17,32 inch 30X32 609.6mmX8 12.8mm (omitted).

18,36 inch 32X36 609.6mmX9 14.4mm (omitted).

19,40 inch 32x40812.8mmx1016mm (omitted).

20, 42 inch 32x42812.8mmx1066mm (omitted).

2 1, 44 inch 32x44812.8mmx1219mm (omitted).

Normal size allows 1 ~ 2mm tolerance.