4 inches is 10*7.6cm.

Usually, photo specifications are expressed in "inches", which is different from the diagonal length of a monitor and other products, and the "inches" of a photo refers to the length of one side of the photo in inches. The "inches" refers to the length in inches of one side of the photo.

For example, a 6-inch photo is a 6 x 4-inch photo. And there is a common international method of expressing the size of the photo, that is, take the short side of the photo of the inches of the integer value plus the letter R to express. For example, 6-inch photo, the specification is 6 × 4 inches, that is, 4R.

Expanded:

The length and width of an image size is measured in pixels, and in some cases in centimeters. Pixel and resolutionPixel is the most basic unit of digital image, each pixel is a small dot, and different color dots (pixels) gathered together into a moving picture, digital cameras often use pixels as a grade classification basis.

But many people think that the number of pixels is the number of light-sensitive points on the CCD photosensitive unit, in fact, this statement is not entirely correct, many manufacturers through special technology, can be in the same light-sensitive point of the CCD photosensitive unit under the production of higher-resolution digital photographs.

Image resolution is the size and dimensions of the image that can be selected by a digital camera, in dpi. 640 x 480; 1024 x 768; 1600 x 1200; 2048 x 1536 are commonly used, and in the imaging of the two groups of numbers, the former is the width of the picture, the latter is the height of the picture, and the two are multiplied together to give the pixels of the picture. are multiplied together to give the pixels of the image. The aspect ratio is generally 4:3.

In most digital cameras, you can choose to take pictures at different resolutions. The more pixels a digital camera has, the greater the resolution of its pictures.

Resolution is directly related to the pixels of the image, a picture with a resolution of 640 x 480, then it has a resolution of 307,200, which is often referred to as 0.3 megapixels, while a picture with a resolution of 1,600 x 1,200, it has 2 million pixels. In this way, we know that the resolution represents the unit of the number of points that the picture takes up in length and width.

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