what it means?3.5mm 1:2.8?(it is written on my mobile`s camera)?

Question

Also whtb is 640 x 480 Resolution ?
Is this better or this?352x288

Answer 1

3.5mm is the focal length of the lens, the effective distance between the lens and the image sensor. It doesn't mean much by itself but can be used to estimate the field of vision, or how 'wide' the lens is. Since your camera is so small, it's probably a slightly wide angle.

1:2.8 is the aperture of the lens, or the relative size of the hole the light enters through. Also written as f/2.8. It means the same to photographers no matter what size your camera is.

640x480 is the size of the picture in dots, across and down. If you were to email the picture to a computer, it would be about the size of a postcard on most screens.

Answer 2

3.5mm doesn't ring any bells. If it said 35mm, it would indicate a wide-angle lens.
1:2.8 is the light sensitivity. 2.8 is pretty good. In fact, it's better than a lot of cheap zoom lenses on SLR cameras.
640x480 resolution means that it's okay for small pictures on websites but terrible for making prints. It's better than 352x288, however. The bigger the numbers, the more detail it captures.

Answer 3

Image resolution describes the detail an image holds. The term applies equally to digital images, film images, and other types of images. Higher resolution means more image detail.

Image resolution can be measured in various ways. Basically, resolution quantifies how close lines can be to each other and still be visibly resolved. Resolution units can be tied to physical sizes (e.g. lines per mm, lines per inch) or to the overall size of a picture (lines per picture height, also known simply as lines, or TV lines). Furthermore, line pairs are often used instead of lines. A line pair is a pair of adjacent dark and light lines, while lines counts both dark lines and light lines. A resolution of 10 lines per mm means 5 dark lines alternating with 5 light lines, or 5 line pairs per mm. Photographic lens and film resolution are most often quoted in line pairs per mm.

Image resolution on raster displays
A television or raster image display with 525 scan lines makes a picture with somewhat less than 525 TV lines of resolution. The ratio of lines of resolution to the number of format lines in known as the Kell factor, after Raymond D. Kell, who worked out details of visual resolution in scanned systems at RCA in the 1930s.

Pixel resolution
The term resolution is often used as a pixel count in digital imaging, even though American, Japanese, and international standards specify that it should not be so used, at least in the digital camera field. An image of N pixels high by M pixels wide can have any resolution less than N lines per picture height, or N TV lines. But when the pixel counts are referred to as resolution, the convention is to describe the pixel resolution with the set of two positive integer numbers, where the first number is the number of pixel columns (width) and the second is the number of pixel rows (height), for example as 640 by 480. Another popular convention is to cite resolution as the total number of pixels in the image, typically given as number of megapixels, which can be calculated by multiplying pixel columns by pixel rows and dividing by one million. Other conventions include describing pixels per length unit or pixels per area unit, such as pixels per inch or per square inch. None of these pixel resolutions are true resolutions, but they are widely referred to as such; they serve as upper bounds on image resolution.


wikipedia.com