Traditional Culture Encyclopedia - Photography and portraiture - Distinguish the authenticity of Fuji J2
Distinguish the authenticity of Fuji J2
Dead Pixel: a digital camera is imaged by millions of photosensitive units on the imaging elements of the digital camera (generally referred to as CCD or CMOS (few)), and one of the photosensitive units is damaged, or works abnormally and cannot image, so it becomes a bad pixel. Bad points are generally irreparable. It is emphasized that if there are any bad points in the test of the new purchase machine, it must be replaced.
third, regarding whether the machine is refurbished, after you get the machine, carefully observe whether there are scratches, fingerprints, dirt or other things in the gap, and whether the metal sheet of the battery cover has been used. When you open the machine for the first time, you will be prompted to set the system, paying special attention to whether the lens is worn.
fourth, detect the camera
hot pixel: both CCD and CMOS photosensitive elements have the problem of thermal stability, which is related to the imaging quality and temperature. If the temperature of the camera rises and the noise signal is too strong, it will form mottled spots on the screen where it should not be. These are the dry spots we are talking about. Various brands and models of cameras have different ability to control dry spots. The same model of cameras also has certain individual differences, and some cameras have the function of reducing dry spots. But the problem of dry spot is a problem that all DC can't completely overcome now (increasing the sensitivity (ISO), especially when the exposure time is long or the camera temperature rises).
The method of testing ccd noise and bad spots by purchasing new dc (more detailed)
We found that people are very concerned about how to test the noise bad spots before buying the machine, which is understandable, because the bad spots/noises are related to the imaging quality, night shooting ability and even whether to repair a digital camera. So I will briefly talk about the noise test method when buying a new digital camera. Because the noise of SLR is less and the buddies who buy SLR are all experts, we will not discuss SLR, and SLR can actually be tested as an ordinary full manual machine.
consumer-grade dc is divided into manual-free, partial manual and full manual (you can control the aperture shutter yourself). They are a little different in testing. Let's introduce it step by step:
1. Turn on the camera, warm it up for 1-2 min, use this time to enter the menu, turn off the date printing function (the new machine is off by default, and it is not new when it is turned on), turn off the noise reduction function (the default), turn off the image effect (sharpness, contrast, clarity and saturation are all turned on to normal), turn off the reverse film effect and automatically balance. Then cover the lens cover, and the machine without the lens cover firmly covers the camera lens with a flat, dark-covered, thick book. If possible, surround the lens with a black cloth. The image format is jepg fine, which is most commonly used. Some fully automatic machines automatically open the shutter to reduce noise as soon as it is slow, and the solution is discussed in the second article.
2. Start the test now. Do not zoom. First, test the bright noise/bad point at the lowest iso. Other iso test methods are exactly the same, and are omitted. Needless to say, all manual and partial manual, you can manually change the iso to the lowest. There is no manual camera, and we will talk about the method later. Use the fastest shutter, common shutter (1/25s, 1/125s, 1/3s, 1/15s to 1s) and the slowest shutter to shoot several all-black films to test the bright noise/bad spots of ccd. Fully automatic machines can't determine the shutter, so take a picture in night mode instead of the slowest shutter sample (iso is generally the lowest at this time, but some machines will automatically turn on noise reduction); Use night portrait mode (blocking flash) to take a sample instead of 1s shutter; Use automatic gear (P gear) and turn on the flash (automatic flash mode, remember to block the flash) to take a sample instead of 1/6s; Replace 1/125s sample with landscape mode; Replace the fastest shutter sample with the motion mode (if any) (if no, forget it). The above alternatives will not be turned on except for the night scene mode. Don't worry.
the above tests are all light noise/bad spots, which reflects that the electric coupling elements of ccd can cause light noise/bad spots due to leakage, short circuit and breakdown. The so-called bright noise/bad point is the point on the ccd that is always abnormally overexposed. It is also necessary to test the dark noise/bad spots below, which reflects the burning, open circuit, even oil leakage and ash entry of ccd elements. On the contrary, dark noise/bad spots are the spots on ccd that are always insensitive to light.
3. Open the lens cover or remove the object blocking the lens, and start testing the dark noise/bad spots of ccd. Many people don't test this, but I have tested it for many people and found that many of my friends have encountered this situation, which sometimes affects the quality of photos, but after the replacement period, they regret it, so I have to say it here. Remember: dark noise is probably caused by ccd dust/oil leakage, if your machine is not new. Aim your machine at a piece of pure white, clean white paper. The lighting of white paper is better. Use a small desk lamp to increase the lighting. Fluorescent lamps use automatic white balance, incandescent lamps use incandescent lamps (halogen lamps) white balance, and other settings remain unchanged. Fill the frame (viewfinder) with white paper, and keep a distance of about 2cm to prevent the machine and hands from blocking the light in order not to get too close.
For a fully manual machine, the shutter speed is gradually accelerated from 1s to above to shoot all-white test films. Remember that the key is to overexpose the white paper by more than 2.5 steps (the machine will mistakenly treat the white paper as 18% gray level instead of % gray level! ) Refer to the manual exposure meter, adjust the aperture to overexpose for more than 2.5 files (preferably overexposed for 3 files) to shoot all-white films. Gradually increase the shutter speed until the aperture can not meet the overexposure of more than 2.5 steps. This process can be realized by shutter priority and exposure compensation. This series of tests estimates that the shutter speed can reach about 1/6s. Of course, there must be someone who wants to know how to test the dark noise/bad point under the faster shutter, but it is not necessary. Brothers who must try, first, you can increase the lighting of white paper, and second, you can cooperate with the flash (set top/external connection). Forcibly turn on the flash, and if it can change the output power best (for example, fz2), increase the output power of the flash by more than 2.5 steps, and use the shutter to shoot all-white films first. For machines that can't control the power of the flash, turn on the flash forcibly and open the aperture by more than 2.5 steps. If the default aperture of your machine is already the maximum when using the flash, it will be a disaster, and it is useless to extend the shutter. Because the shutter in flash photography has lost its control over the exposure of the subject. In the case that the flash can be synchronized, the shutter speed that various machines can achieve is different, but it can generally reach 1/25s (consumer dc is generally a vertical focal plane shutter). Faster shutter can only use advanced flash, so let's not test it again! Anyway, we got a series of all-white test films.
Without a manual machine, you can also shoot test films in various modes (scenery, portraits, banquets, beaches, etc.) by using exposure compensation. Remember to increase the exposure by more than 2.5 files. You don't need to increase exposure when shooting in night scene mode, which can replace the test of the slowest shutter.
4. Finally, the software detects these all-black/all-white proofs. Transfer all the black and white films just shot to the computer (the test was transmitted to JS's computer at that time). First, use acdsee, photoshop and other software to open all white proofs, reverse them into all black films and then store them back (don't mix them up). Then use Dead pixel test software to test all-white/reverse all-white proofs. First, set 6/25 with the default parameters. Anything over 6 is light/dark noise. Remember their coordinates. More than one fixed noise can be changed at that time, and more than three fixed noises must be changed within 7 days after purchase. If you exceed 25, you must change it. For the noise in the reversed black film, if there are many noises connected together, the old machine is likely to have ccd dust/oil leakage. If you want to compare the noise control ability of various cameras (there is no noise above 6), it is recommended to test each sample with a parameter of 5/2. The less noise, the same noise control ability of this camera in theory (the same shooting parameters).
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