The right exposure - in-depth understanding of tolerance.

Iceland in July 2003 meeting, I had the honor and Thomas Knoll (the famous, Adobe Photoshop and Camera RAW main author) to digital video signal to noise ratio relative to the issue discussed. .In Iceland 3,000 km journey by car, our topic involves a large number of digital image processing and other issues. .Thomas talked about the one I never thought about before the issue, <p> Iceland in the July 2003 meeting, I had the honor and Thomas Knoll (the famous, Adobe Photoshop, and the main author of Camera RAW) for the phase noise of digital camera .than the problem discussed. .In Iceland 3,000 km journey by car, our topic involves a large number of digital image processing and other issues. .Thomas talked about the one I never thought about before the issue, and this problem when it comes to great insights to me immediately. .</ P> <p align="center"> </ p> <p> on the dynamic range of </ p> <p> First, let us discuss the convenience to the dynamic range of digital SLR cameras into the corresponding aperture surrounded by 5 files .(actually should be nearly 6 files, but there is no need to care about too much here), 5-speed camera outside the dynamic range to beyond: the not underexposed (dark no details and levels) is overexposed (no details and highlights .level), which is probably why a lot of software will be divided into five regions of the histogram one of the reasons it. .Usually we are dealing with is actually a 12-bit RAW images (well, in theory, should be 16, but now all digital SLRs are in real space using 16-bit 12-bit RAW recording data - is always better than JPG .8-bit). .To reflect the 4096 12-bit RAW (2 of 12 power) discrete brightness values. .This may be reminiscent of, if the equivalent of 5 f-stop dynamic range to cover the 4096 brightness, then the coverage of 850 per file = 4096 / 5, the fact that the case? Always remember, "half" here .also effective (2, N th power), the dynamic range of digital SLRs is equivalent to 5 f-stop, the first of a file (the brightest part) covers the 2048 colors - why is that? This is because the digital SLR .The CCD or CMOS signal recorded is linear, and f-stop dynamic range, equivalent to 5 per 1 file will be on the upside than the half light, while leaving the remaining half of the next file. .The following table gives a more detailed explanation: </ p> <p align="center"> </ p> <p> This table shows a lot of questions, the most important one of our most common error is made, .If we do not make good use of the far right of the histogram that area (usually we see the histogram were divided into five regions), in fact we wasted in the hands of expensive digital SLR almost half of the dynamic range! .Of course, we all know (or at least should know) is the digital camera exposure over most taboo - the brightness beyond the dynamic range, playing negatives have such experience. .If overexposed, meaning that the brightness of picture beyond the far right of the histogram, then we can only say bye-bye picture was. .</ P> <p> about for a long time, simple to summarize: digital and film the biggest difference is that digital SLR should try to take advantage of the histogram file in which the brightest, because it covers half of 4096 levels of brightness .2048, and in the histogram, we usually see this file, only one-fifth of the histogram. .From the perspective of the histogram, digital SLR need the right exposure, but usually require the exposure of ordinary film center. .</ P> <p align="center"> </ p> <p> by the preceding analysis is not difficult to understand the "right light" means: the possible distribution of the histogram to the right, but at the same time .can not be overexposed to ensure that (co-fed). .Look at this point from the operational level is actually very easy to do, most of the cameras LCD screen in the check image, flashing signs will be the site of photo overexposure. .If there have been a little adjustment to the exposure of the camera's shutter or aperture (see which is more important) one again until the overexposed prompted disappeared. .(Personal point of view this approach is still feasible but the best accumulated through experience and a successful, because some moments that might last a life time. Also note that, although the RAW tool can adjust the brightness of the digital exposure compensation and the like, but .types of compensation is limited: it can not be over-exposed some of the details and then moved back: RAW CCD or CMOS directly records the information on the CCD or CMOS, but if there is no record because the details of overexposure, RAW processing is back days later without .surgery was)..