The simplest way: shutter speed affect exposure exposure affected shutter speed and aperture size, exposure time with the popular parlance of the shutter speed is the same, so you will produce this question, but there is no official statement exposure time of this statement, It should be said that the amount of exposure rather than the exposure time. If you have to say the exposure time, we must put aside the impact of the iris. You can be understood, when the same aperture, the shutter speed, the exposure time is short, the shutter speed is slow, the exposure time is long. For example: when F2.8 aperture, shutter speed than the shutter speed of one thousandth second hundredths of a second, short exposure time is generated. Said the following about the amount of exposure: You know the camera is actually a film (film camera) or CCD (digital camera) to save up light projection, the amount saved on the film or CCD light effect photo of light and shade, if saved few would dim light, if you save a lot of light on the bright side. And the amount of light but not too much you can say exposure of normal, above normal exposure is excessive, is less than normal due to exposure. The camera is the amount of exposure by the shutter and aperture control. Borrow someone else's metaphor to talk about, this camera is like a faucet, the size of the amount of water equivalent to the amount of exposure, you can control the amount of water the size of the switch by a certain time and adjust the size of the pipe diameter, and this is equivalent to the tap of the camera shutter switch speed, aperture diameter is equivalent to the camera. When you are in the same caliber, the longer open time greater the amount of water; at the same time you drive, the greater the amount of water pipes of greater caliber. In summary (-_-! Like writing papers), the amount of exposure decided by both the shutter speed and aperture size. So only say that the exposure time is not appropriate, it should be said exposure.
Recent research camera in the drive, and often see the camera IC output format as RGB, YUV / YCrCb, a concept I do not understand is YUV and YCrCb in the end what is the difference? Or whether they are the same concept, but the alias is different, so I searched online for a long time, finally got a more satisfactory answer.
Original Address: http://forum.eepw.com.cn/thread/84775/1
Question 1: What is YUV?
Question 2: YUV, YCbCr4 YUV (4: 2: 2) and YCbCr4: 2: 2 format whether it is for a thing?
Question 3: YCbCr4 support ITU601: 2: 2 format and general YCbCr4: 2: 2 format What is the difference?
Answer 1:
Details about the YUV (also known as YCrCb) is being used by European television systems a color coding method (belonging to the PAL system). YUV is mainly used to optimize the transmission of color video signals, making it backward compatible with old black and white television. Compared with the RGB video signal transmission, its biggest advantage is that only very little bandwidth, but requires three separate RGB video signals transmitted simultaneously.
In the YUV, "Y" representative brightness (Luminance or Luma), i.e. grayscale value; and "U" and "V" is represented by chromaticity (Chrominance or Chroma), is to describe the image color and saturation for designating color of the pixel. "Brightness" is created by RGB input signal, the particular portion is superimposed with the RGB signal. "Chroma" defines the two colors - hue and saturation, respectively denoted Cb and Cr. Wherein, Cr reflects the difference between the red part of the RGB signal values of RGB input luminance signal, Cb and reflects the difference between the RGB input signal portion and a blue luminance values of RGB signals, namely the so-called color-difference signals, i.e. we often say that the component signals (Y, RY, BY).
In the professional field, "Y CB CR" represents the digital color difference signals rather than analog color-difference signals. Color difference signals Y, RY, BY signals are generally known as Y, Cr, Cb; Y Traditionally, Cr, Cb digital (PCM) of the color difference signal, analog color-difference signals called Y, Pr, Pb, we often DVD Player internal seen Y, Cr, Cb and to see the color output labeled Y, Pr, Pb or YUV outside of DVD Player; YUV color difference signal is known in Europe the PAL television system, including digital and analog He said the YUV color difference signals, so when you see that you will YUV think it is PAL system Y, RY, BY signals, it may be digital (PCM) is YUV, it may be analog YUV.
Answer 2:
That is the difference between analog and digital differ in habit:
"the Y-Traditionally, Cr, Cb digital (PCM) color difference signal, analog color difference signals called Y, Pr, Pb, so we often internal DVD Player to see the Y, Cr, Cb and see color output labeled Y, Pr, Pb, or YUV outside of DVD Player; "
may actually be the same:
" YUV is the color difference signals in PAL television systems in Europe the generic term includes digital and analog color difference signals are called YUV, YUV so when you see that you would think it is the PAL system Y, RY, BY signals, it may be digital (PCM) of YUV, also It may be analog YUV. "
Answer 3:
YUV and Y, Cr, Cb for digital circuits,: YUV and Y, Cr, Cb only a difference 128, YUV not negative, Y, Cr, Cb highest bit is the sign bit, U = Cr + 128; V = Cb + 128. see iru bt656 or ccir 656
Bayer data processing
Original Address: http://www.cnblogs.com/lin1270/archive/2010/12/01/1893647.html
Bayer is inside the camera raw images, the general suffix .raw. Many software can be viewed, such as PS.
We .jpeg down your camera or other image formats stored on the memory card, are transformed from .raw format
Over. There are a variety of internal storage .raw format, but no matter what, are the first two lines of the different permutations of its
Format may be as follows:
G R G R G R G R
B G B G B G B G
G R G R G R G R
B G B G B G B G
2 is a multiple of the horizontal, vertical multiple of 4, which constitute the resolution. As above represents the resolution of 8 * 4
Bayer 图.
We want to know is, twice as G = 2 * R, and G = 2 * B, i.e., red green or blue value, because
The human eye is more sensitive to green, so green more weight.
Below that the conversion from rgb to FIG bayer algorithm, FIG RGB, that is, three-color map, a pixel on the RGB
Color mixing three colors, and a pixel bayer FIG only one color, or R or G or B. Because bayer
A pixel only one color, the need to use it around the interpolated pixel color (fill) additional
Two colors, the color itself would not have put a general algorithm:
For insertion R and B, and
Rx = (R1 + R2) / 2; ------------- taking the average or the upper and lower, or the average of the left and right
Rx = (R1 + R2 + R3 + R4) / 4; ---- averaging four sides
Similarly as B:
G B G
R G R
G B G
For intermediate G, which is missing R and B, and evaluated with an average value of vertical and lateral.
for
B G B
G R G
B G B
FIG do this, the intermediate point R, G and B is missing, being no discussion G, B so, averaging is carried out from four corners of R B.
==============================================
If the insertion G, and slightly complicated.
But most of the R and B with the same algorithm, complex algorithms, its complexity is also doubled, but more accurate, if for
Video monitoring systems, accuracy is not necessarily required relatively high, to a solution of R or B below said complex:
For Figure:
R1
G1
R4 G4 R G2 R2
G3
R3
The intermediate points R, G, and it is necessary to insert B, B does not discuss, discusses G, which has four peripheral points G1, G2, G3, G4.
(G1 + G3) / 2 -------------- if | R1-R3 | <| R2-R4 |
G (R) = (G2 + G4) / 2 ------------- if | R1-R3 |> | R2-R4 |
(G1 + G2 + G3 + G4) / 4-- if | R1-R3 | = | R2-R4 |
If the surrounding pixel color is B, the comparison should be | B1-B3 | and | is | B2-B4.
====================================================
Moreover, on the algorithm to convert RGB format to the YUV format, we do not want to discuss here.
Here we must note that the value of bayer each pixel is 8 bits. But some of bayer format camera there 10, 12
And 14, 16, then how to convert these higher than 8-bit data to 8-bit data?. Take 12 data for some
Who is to take high-low eight or eight, then this will be a problem, this image will have a slope, not a bright side is biased
Dark, or if there were other problems mess, color problem is not always satisfactory. This time we will go to the more positive it is undoubtedly
A waste of time.
Another method is to use log mapping, according to foreigners say that this method has a high conversion accuracy Take 12, a general conversion algorithm:
f(in) = 2 ^ ( log(in) * 8 / 12 )
Conversion Pictured:
|8 .
| .
| .
|_______________________12
Because log256 = 8, log4096 = 12, based on a log base 2 oh.
Do better algorithms may be based on other factors such as exposure to provide different, but the algorithm is adjusted so that when some unexpected
When an event occurs, the picture will not produce serious distortion.
