Starry Sky

By the negative effect of the 'starry sky', photographers usually mean a collection of hot and broken pixels, which resembles a real sky with billions of stars. The photo below shows a 1: 1 crop for a very long shutter speedon which such an effect is strongly manifested.

Starry sky created by Canon EOS Digital 350D camera at ISO 1600 and shutter speed of about 1 hour.

Canon EOS Digital Camera Starry Sky 350D at ISO 1600 and shutter speed about 1 hour.

I want to warn you right away that this article only deals with hot pixels. Unlike 'dead' or 'dead' pixels, their number and intensity of luminescence increase with increasing ISO and / or with increasing excerpts. At low ISO and / or relatively short shutter speeds (up to 30 seconds), hot pixels may not manifest themselves in any way and are a kind of time bomb. Dead / dead pixels are always present in the pictures, with any settings.

Hot pixels make a huge contribution to the overall digital image noise. The difference between hot pixels and normal digital noise is that hot pixels usually appear only at slow shutter speeds and even at ISO 50 or ISO 100. Usually hot pixels are lonely, but with very slow shutter speeds, their number increases, as shown in the examples from this articles.

Personally, I rarely shoot at very long exposures, and therefore I do not encounter the problem of hot pixels. But here are photographers who use very long excerpts, for example, in astrophotography, more than once faced with the fact that even at the lowest ISO values ​​appear hot pixels.

Below are examples of shots taken at very slow exposures in 'BULB' mode (manual excerpts) During exposure the camera mount was closed with a conventional bayonet cover. Unfortunately, the Canon EOS Digital 350D и Canon EOS 5D not quite correctly record the duration excerpts in BULB mode, but I can assure you that Exposition spent about one hour. So very long excerpts were used only to maximally demonstrate the strong effect of the starry sky, in real life they are rarely used.

Link to the archive with the originals. Pictures were taken in RAW + JPEG mode with different settings for noise reduction functions.

The examples of photographs show that the matrixes of cameras suffer not only from the effect of the 'starry sky', but also have serious 'flare' at the corners and sides of the matrix. Due to the fact that matrices Nikon D80, Canon EOS 5D and Canon EOS Digital 350D have the usual Bayer structure, the resulting hot pixels correspond to one of the shades of red, green or blue, since usually one of the subpixels a certain shade.

Despite the rather terrible picture of the "starry sky" of my cameras, I do not have any serious problem for real everyday shooting. I am pretty easy on hot pixels. My experience tells me that the number of hot pixels can increase over time and should not be seriously feared. When shooting at fast shutter speeds, the occurrence of hot pixels is extremely rare.

Hot pixels can be treated fairly easily by enabling 'long exposure noise reduction'. This function removes hot pixels with one trick - after the end exposure the main shot, the camera exposes the additional shot with the shutter closed, equal in time to exposure main frame. In the second, additional frame, which is not written to the memory card, the camera's processor finds hot pixels and 'subtracts' them from the main picture. The function works very well and even with such an apocalyptic sky, as shown in my examples, it copes with a bang, including removing side flares from the matrices. But she has one serious problem - the shooting time is doubled. And if the photographer used a shutter speed of two hours, then in the end he would have to wait another two hours for the camera to take an additional corrective shot.

Some cameras have modifications of this function for which the camera simply memorizes the 'star map' once and subtracts it from all subsequent images. This hot pixel map can be updated via the camera menu. Functions based on the creation of such 'maps' are usually called a general term - 'remaping' (from the English 'Remapping'). If you shoot in RAW format and process the filmed material on a computer with modern powerful tools for working with RAW files, then the remap function is turned on automatically. Modern processing programs are quite good at detecting hot pixels and removing them.

Two parts of the same picture with and without remapping. Auto Remapping with Adobe Camera Raw

Two parts of the same photo, with and without remapping. Automatic remapping with Adobe Camera Raw. This snapshot can be found in the archive with originals under the name 'IMG_1265.CR2'

Also, hot pixels are partially removed by the 'High ISO Noise Reduction' function. This function can detect a hot pixel as a normal part of digital noise and programmatically remove it.

I will describe one interesting observation of the noise reduction function at high ISO sensitivity using the example of a camera Nikon D80... In the menu, this function is called 'High ISO NW' and four operating modes: 'Norm Normal', 'Low Low', 'High High', 'Off'. And if you click on the help button, you can see an interesting explanation of how this function works:

Process pictures taken at sensitivities above ISO 400 equivalent to reduce noise (ripple). The capacity of the memory buffer decreases as noise is removed from pictures. Note that when 'Off' is selected for High ISO NN, noise removal is still performed at sensitivities above ISO 800, although the amount of noise removed is reduced.

In short, at ISO 800 and above, the camera always uses noise reduction. As a result, you won't be able to get a 'naked' JPEG file at a high ISO value. The most interesting thing is that due to forced noise suppression, sometimes there is a situation when the noise at ISO 640 is higher than at ISO 800. In the gallery from this article there are two pictures with Nikon D80 at ISO 640 and at ISO HI-1 (equivalent to ISO 3200), forced noise reduction made the picture at ISO 3200 cleaner.

Many years ago, I saw some cameras tested for noise. In those tests, after passing the average ISO values ​​on which the camera could work, the graphs showed a jump with a decrease in noise, and then again its further growth. Then no one could solve the riddle of such matrix behavior. But the solution most likely lies precisely in the fact that when shooting in JPEG after a certain ISO value, automatic forced noise reduction is turned on, which makes the picture cleaner.

By the way, forced noise reduction does not only apply to Nikon D80, most Nikon cameras always produce noise reduction at maximum ISO values. Each camera has its own separate threshold, from which forced noise reduction is turned on. As for cameras of other brands, I have no exact information.

Also, many cameras have an ISO threshold to which noise reduction will not be carried out, even if the noise reduction function at high ISO is turned on manually. For example, here's what you can find in the camera menu Nikon D700 about the 'Under. noise for high. ISO ':

Reduces noise at ISO 1600 or higher (also reduces the number of pictures that can be taken in a single burst). Even when 'Off' is selected, minimum noise reduction will be performed at ISO sensitivities HI 0.3 or higher.

It turns out that Nikon D700 noise processing starts at ISO 1600, while Nikon D80 at ISO 400.

And one more observation about the Canon EOS 5D - in the pictures it is noticeable that hot pixels in the 'starry sky' accumulate in special constellations and even the 'Keno Milky Way :)' is visible in the center of the picture.

Milky Way?

Milky Way? This photo is enhanced with contrast. The rest of the photos are in the article without any additional processing. The original of this snapshot is archived under the name 'IMG_5374.CR2'

Hot pixels do appear even at the lowest ISO values, you just need to make the shutter speed longer (see the file 'IMG_5372.JPG' from the archive with the sources).

Noise reduction is turned off in the archive file has the name IMG_5377.CR2 / JPEG

Noise reduction is off. The file in the archive is named 'IMG_5377.CR2 / JPEG'

In real shooting conditions, all these hot pixels will simply be superimposed on the resulting image :(.

Feel free to experiment with your digital cameras. To do this, simply cover the camera bayonet, or the front lens cap, find 'Bulb' or 'B' or 'Time' mode and shoot at really long exposures and different noise reduction settings. and at different ISO values. The 'Bulb' mode can most often be selected in mode 'M' after setting the slowest shutter speed (30 or 60 seconds).

I propose in the comments to discuss the following questions, to which I do not have a clear answer:

  1. Does the number of hot pixels increase with the age of the camera, i.e. Is there an effect of 'matrix burnout' from its constant work?
  2. What determines the appearance of new hot pixels?
  3. What matrices - CCD, CMOS, FAVEON, LBCAST, etc. more resistant to hot pixels? How secure is film against this digital ailment?
  4. What causes the 'flare' at the corners and edges of the image, which is described in the article?
  5. What kind of vertical stripes appear in pictures with Canon EOS 5D?
  6. Do some Canon, Sony, Pentax cameras force noise reduction at high ISO if the noise reduction function itself was turned off?
  7. How to clearly distinguish digital noise and hot pixels at very long exposures? Or is digital noise at long exposures composed entirely of hot pixels of varying degrees of 'hotness'?

↓↓↓ Like it :) ↓↓↓ Thank you for your attention. Arkady Shapoval.

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Comments: 122, on the topic: Starry sky

  • Lef

    A friend has a Nikon D5000 with just a monstrous flare on the side of the frame, even at short shutter speeds and small ISOs, from 400 it seems already noticeable during daytime shooting. By the way, it's a shame that on the old soap dish Olympus S115 was in the “pixel mapping” menu, and Nikon's DSLRs get rid of hot pixels only in the service

  • Ivan Vatnikoff

    This article smacks of this http://lurkmore.to/%D0%A4%D0%BE%D1%82%D0%BE%D0%BE%D0%BD%D0%B0%D0%BD%D0%B8%D0%B7%D0%BC
    Already I feel like now in the comments srach will flare up.
    Although I am sure that no one is engaged in astrophotography on this forum, well, or a maximum of 1-2 people.
    I dare to suggest that the matrix suffers and burns out from such long shutter speeds for an hour, which leads to irreversible consequences, burnout of pixels, hot pixels and so on and so forth, because it’s not for nothing that companies restrict video recording for 10-20-30 minutes. After all, after such a long work, the matrix is ​​heated so that the display can fry fried eggs.
    So now I do not advise everyone to rush to check on their device for exposures of half an hour or more.
    Pity the technique.
    But I would gladly read comments from acting astrophotographers on this subject purely for the sake of interest.
    Happy New Year everyone! Especially Arcadia who writes articles about the "Canon Milky Way" even on holidays.
    Shoot more, think less about technology and noise at shutter speeds of 1 hour.

    • Alexander

      A limitation on the duration of the video recording is made so that the camera does not legally become a video camera. It seems to me that this is the main reason, although who knows

      • Anatoly

        Right thought

    • Lynx

      Do not confuse the concepts of “knowing your own technique” and photojacking.
      these are very different things.

      • anonym

        Hurt? So it's all right.

        • Lynx

          Not at all. I simply point out the mistake of a typical teenager who had read Lurk, but who couldn’t understand what was said there

          • anonym

            Something boiled and boiled in the lynx in the pelvic area. So Ivan got to the point. The knowledge of one's own technique is the knowledge of its tech. characteristics, and an understanding of shutter speed, aperture and ISO. Everything! Everything else, like, how many hot pixels do I have there at a shutter speed of 120 minutes? This is already a photo genre.

    • Denis

      “The matrix heats up so that you can fry eggs on the display” - so the matrix gets hot or the display? There is no overheating of the matrix from long exposures - I checked it repeatedly on Canon soap dishes with CHDK installed, when it is possible to display the sensor temperature on the display - no heating more than 40-45 degrees was observed. And this is a CCD sensor that consumes (and therefore turns into heat) much more power than the CMOS sensors of most DSLRs. And for that matter, if a temperature sensor is built into the sensor, then there is protection against overheating.
      But I often observed the heating of the entire camera - and the heat went, oddly enough, from somewhere in the battery compartment.
      Further, about video filming, or rather its limitations. On old Canon soap dishes there were the following restrictions - 320x240 - 3 minutes, 640x480 - 30 seconds. So how much of the matrix was the smoke supposed to go through, in 3 minutes or 30 seconds? And why then there is no restriction on working in LiveWiev mode, in which the matrix works in the same video mode? And the answer is simple - these fotiki could not write a file larger than a certain size, therefore there were such limitations. And in many modern cameras the limitations can most likely be related to the size of the resulting files (in addition to the comparison with a video camera described above).

      • Arkady Shapoval

        I suppose that the heating that you can feel with your hands on everything else also comes from the processor and camera electronics, like on smartphones that have a bunch of applications running.

        • Denis

          Yes, some cameras warmed just around the main board, noticed :)

    • Gene jb

      And what does the inclusion of the matrix? In mills, the matrix always works, even when there is no shooting. In the mirrors live view too. Bullshit is everything. The matrix is ​​designed for this. Especially cmos. Ccd will be worse.

  • Nicholas

    The number of hot pixels unambiguously increases with the age of the camera, I have a canon sx20 soap dish with chdk installed, and so recently hot pixels have appeared even at short shutter speeds.

  • Timur

    Regarding the paradoxical increase in image clarity with increasing ISO on Nikon D7100, I can say that at ISO 1250-1600 the picture is worse than at ISO 2500. Therefore, with a lack of light and the impossibility of using a flash, I do not bother with the dilemma “below ISO - less noise, but longer exposure ”, but I just put ISO 2500 and that's it. Well, ISO 3200 can only be filmed conditionally, of course. Thanks to Arkady for clarifying something about matrix noise in his article. Happy New Year everyone!

  • Rodion

    Hmm, interesting article. Also noticed such an effect, removing the sky. I will know how to deal with this.

  • Madness scif

    d300 and d7000 - they suffer greatly from this

    • Alexander

      Equals are the same on both the D7000 and the D7100. In Jpeg, the picture is cleaner only due to the large number of megapixels and aggressive noise reduction. Just need to say thanks to the camera processor.)))

  • Sergei

    Interestingly, do hot pixels always appear in the same place?

    • Rodion

      Logically, it should be so. After all, remapping otherwise would not make sense.

  • Vadim

    The only thing I want to draw attention to is that for the purity of the experiment, when shooting with such slow shutter speeds, as discussed in the article, it is strongly recommended that the viewfinder be covered with special plugs so that the light does not penetrate through it and does not create additional matrix highlights.

    • Arkady Shapoval

      When the mirror is raised, it must completely block the light coming from the OVI. What you are talking about applies to correct exposure metering when working with a tripod, since then indeed the light coming through the JVI can affect the metering sensor. The professional cameras have a special shutter for this. Regarding flares - this is not a problem of light coming from the OVI or from the mount, think about it. Although, you need to check this too :).

      • Pasha Shmakov

        The practice of IR shooting shows that exposure of five minutes on a sunny day without a dummy is enough to get light in the picture.

        • Arkady Shapoval

          I checked, yes, the flare is obtained, but not at all the same as shown in the examples of the photo. And I did the test in a dark room “under the covers” :).

          • Anatoly

            Nikon D700 Owner's Manual Self-Timer Mode topic p. 102
            __________________________________________
            Close the shutter of the viewfinder eyepiece
            before focusing. This will prevent
            the influence of light passing through
            viewfinder, selectable options
            exposure.

    • varezhkin

      +100 for remapping the matrix in the Nikon service also always close the JVI. This should not be neglected.

  • Ivan

    Arkady Do you or your friends happen to know an effective method for dealing with hot pixels when filming? When taking photos, hot pixels do not bother me much with ACR or lightrum extinguishes them, but I still don't know how to kill them in video. Especially the Internet was not wool. Once I came across plug-ins for Adobe Premiere to deal with hot pixels, but then the problem was not acute and I did not download them and did not write down the names. I have two cameras kenon 5d mark 2 and kenon 6d - I recently bought this camera and found hot pixels, can they kill them in the kenon service? until he called them. I am mainly engaged in photography, but sometimes I shoot video and at high ISO 3200, 6400 hot pixels kill all the desire to shoot. Sometimes you have to lift it so high, for example when shooting indoors.
    Thanks in advance for your reply.
    I would also like to see the opinion of people who really solved this problem.

    • Anatoly

      The best thing is to buy a budget camcorder, which is much higher in quality than any professional. CZK, and she shoot a video.
      The large CZK matrix with its small puxel simply physically cannot qualitatively shoot video even in 2K.

  • Ivan

    By the way, for 5 or 6 years of using Kenon 5d, hot pixels appeared on the camera, which Lightroom or ACR did not always correctly delete. In my subjective opinion, there are more of them. If I had not noticed them before, then after about 5 years of use I began to notice them. I must say right away that I did not take measurements during the purchase every year. Purely subjective judgment. But again, with my needs for a photo, and Kenon 5d only takes photos, this did not create any problems. But what to do when shooting video, the question is still open for me.

  • anonym

    Illumination through the JVI occurs at such slow shutter speeds and therefore comes with a plug that can be fastened to a strap, or put into a pocket on old pentax. Some medium-format cameras have an additional shutter behind the mirror, but you still have to fold the shaft for long exposures, or close the shutters on a measuring prism. There were always flashes on the D600 when I shot with the Hoya R72 filter and forgot to close the viewfinder with the cover from the kit.

    Also, for pentaxes, for each ISO value, noise reduction is also configured. After switching to Nikon, this is missing, as are many other very convenient goodies.

    • Arkady Shapoval

      Thank you.

  • Alexander

    I can't even imagine where such exposure is needed for an hour or more. In astrophotography, such exposures are also NOT used, because everything moves and rotates. Even when using mounts, they try not to set the shutter speed too long. ISO is also not bullied, because there is a very good concept as "signal to noise ratio".

    • Arkady Shapoval

      Long exposures, including very long ones, are used, for example, when shooting with a pinhole. And no one says that astrophoto needs exactly such long exposures as in my article. I just presented extreme cases, so that every hot pixel was clearly visible.

      • Alexander

        Ugum ... I can add to the article that the amount of noise directly depends on the temperature of the matrix. The colder it is, the less noise. The best results appear when working at -15 and below. Addiction works - the worse the photographer, the better the matrix =)

  • Sanya

    But I’m interested in something else. Would you like to know us? Users of this site.

    • Arkady Shapoval

      Your question is not clear to me.

  • Oleg

    “Dead / dead pixels are always present in images, at any settings” -
    Not true! I had a broken pixel on the d300s, white, which appeared after 400-800 iso in photos and videos. At low ISO and short exposures, he was neither in the rave nor in the jeep!

  • varezhkin

    I got a hot red pixel on the D50 on any ISO at a shutter speed of 1/30 and longer. I successfully uploaded it myself using my own service software, which for some time has become available on the network (for almost all Nikon models up to and including D800).

    • anonym

      A reference can be? Or tell me how to find it.

  • varezhkin

    Nikon's native programs Capture NX2 and Capture NX-D, by the way, have the “Astro Noise Reduction” function.

    • Alexander

      There is excellent software for dealing with noise, hot / dead pixels, vignette. For astrophotography only. These are DSS and IRIS. Works with Raw. They remove all the defects of the picture so that the native software will envy. The native program has a plus when you need to process one photo. Although I will reveal a "secret", one photo in astrophoto is not enough. Even at the FF they try to take two photos (at least the background and the landscape + gluing in the FS) They shoot in series of 10-100 shots + calibration photos. And this is exactly the moment when noise and hot pixels and vignettes do not exist in the photo even at ISO 6400 and exposure 8-20 sec. Generally. (On the D7000 and “around it”) So the standard concepts of noise in astrophoto work a little differently))) And the native software is to pull Ravka after the “magic” of specialized programs, otherwise CaptureNX2 will take down half of the stars along with the noise! This is with regards to astrophoto. In all other respects, including noise reduction algorithms and color rendition when processing ordinary photos - IMHO, there is no replacement for the native software. These are the paradoxes))))) Happy holiday everyone! =)

  • Vladimir

    Would you guys go to the kitchen better for a hundred grams ... do not write such comments and even go and spoil the matrix, check ... NAFIGA? Happy New Year !!!

  • Oleg

    Well, why it is quite informative, do not get involved in video shooting on the camera and long shutter speeds all this ruins the matrix. Happy New Year everyone!!!

    • Alexander

      Do not ditch this matrix! Do not scare people. Now video clips are filmed on a DSLR and all the buzz. All functions in the camera are technically thought out and do not do any harm to the device itself!

      • Lynx

        You see - 15-30 minutes of video recording and an hour and a half hour photo exposure are different things.

      • Lynx

        And who said that videographers do not ruin the matrix ??

      • Oleg

        If there is a matrix heating during video shooting, then its wear is probably coming, because there are no fans for cooling, as I understand it

        • sergey

          the processor and other similar chips made of the same silicon are also very hot and work until they are morally old and thrown out

  • Ruslan

    Once I found instructions on the Internet for Canon EOS cameras.
    I checked it on my canon 600D (you could see a hot red pixel in the video), the instruction worked - the pixel was gone:

    “If after buying a camera you have lost a healthy sleep, and you are constantly tormented by the ubiquitous dead pixel - it doesn't matter! The following instructions will help you restore healthy sleep and “virginity” of the matrix:
    1. Be sure to close the lens with a cap (there is an opinion that with a plug (without a lens) the remap does not work).
    2. Close the viewfinder with your finger (to exclude the possibility of accidental flare) and take a RAW + JPEG picture (ISO 100).
    3. Go to the menu, select the item "Sensor cleaning: Manual", "OK", wait 60 s, turn off the camera
    4. Again, always with the lens cap closed, take a RAW + JPEG picture (ISO 100)

    Comparing the shots, the problematic pixels should disappear, and at higher ISOs there will be a little less noise. ”

    Maybe someone will come in handy ...

  • Gene jb

    I will try to answer
    1. Increases. It is associated with aging. It's no secret that the matrix is ​​constantly exposed to alpha, gamma, etc. radiation. Of course, this is not space, but therefore aging is not so fast. Opportunity has already lost his memory ...
    2. The answer in paragraph 1.
    I will answer the remaining points with one answer - Arkady, you are mistaken. There are no hot pixels here. I see hot pixels on my camera, they appear at shutter speeds from 30 seconds higher. But they don't look like that at all. These are specifically dead pixels. Bright and contrasting. And your photos are just noise. Normal noise. And at very long exposures it is infrared noise. The matrix removes its own heat. Although the camera can take such exposures, it is absolutely not designed for this.
    Why wasn't Ivan called a katsap? It's trendy now ...

    • Arkady Shapoval

      Maybe he was mistaken, in fact, this was the 7th question.

    • Lynx

      Interesting opinion .. explains a lot

  • Gene jb

    I wanted to add that I don’t use jpg on 400d, so I don’t know if there is noise reduction or not. And on long vyd. disconnected, interferes greatly. It’s easier to crush then, especially since DPP does this almost automatically. Adobe, by the way, works worse with snapshots, I noticed it more than once. I suggest you write an article about comparing native DPP and adobe cr or lightroom.

    • Arkady Shapoval

      okay, next time I suggest not to ask questions about Ivan, now I am very hard at banning such topics on all pages of the site, except “question answer".

      • Gene jb

        Well, you started, not me. In general, I would talk with sane Ukrainians on such topics, I would like to clarify a lot. And then no matter how I start to communicate, it feels like I'm talking to zombies. But not here of course.

        • Arkady Shapoval

          Excuse me, dear guest, where and what did I start?

          • Gene jb

            Vatnikoff ...

            • Arkady Shapoval

              Ahaha, excuse me, but I did not start, questions to Vatnikoff.

  • Neofot

    Not all questions I have an answer, but some opinions:
    1 Very much depends on the quality of the matrix. If good, then no - it is still made of silicon (albeit modified). But since this is high-tech, everything is decided by the quality (the higher the technology, the more it depends on different nuances). Burnout is impossible because microcurrents CANNOT heat silicon strongly.
    2 New, I think from the battery. Original or not. There is hardly a stabilizer there. The voltage drops in the camera's network are not critical for electronics, but for the matrix it is not a fact, and it is not a fact that in some places and in some way made batteries do not give voltage or current drops (the latter is more critical). If I were a professional photographer, I would NEVER use non-original batteries.
    3 I think that CCD matrices are weaker than CMOS - more current is applied to the former. The film ... depends on the grain size thereof (chemical composition - primarily the degree of its purification from impurities). I think that prof. the film with 100 iso is devoid of grains.
    4 Flares on the edges, I think, from the fact that the silicon of the matrix has a larger electrical contact on the sides. If it is not even a straight line, then the electric magnetic field works. The signal is distorted. Or simply uneven heating and, as a result, changes in electrical conductivity. In any case, the point is not in the matrix, but in its “environment”, in the narrowest sense - the body kit.
    5 I do not know, but the reasons may be those described in paragraph 4. + More signal processing features are available for this model (or this instance)
    6 I am sure that yes, and on prof. the cameras are unlikely to be clearly, but on ordinary I think, almost without disguise. Moreover, the declared frame rate of not more than 4,5 per second allows this.
    I think you can look for a firmware that allows you to remove it altogether (I don't know if you can “hack” the firmware and customize everything for yourself).
    7 If the ISO is low (100 for example), then there is nowhere for digital noise - the signal is not amplified at all, or amplified very slightly. Therefore, my opinion is that at low ISO + very long shutter speeds = only hot pixels.
    With respect and gratitude to you, Arkady.

    • Denis

      2. All elements for which a change in the supply voltage is critical have stabilizers. What does the difference in amperage of batteries mean? The current strength depends on the power consumed by the device, a jump in the positive direction (voltage increase) will not give any battery, and in the direction of decrease it will not be detrimental to the device, since the current strength will drop. In the presence of stabilization, a voltage drop to a certain limit for the element will not affect at all, and below the lower limit the camera will simply be cut down.
      7. Noise is ALWAYS and at any ISO. Another thing is how much it can be seen - it already depends on the quality of the matrix, many matrices create quite visible noise for themselves already at ISO 100. And this noise is taken not at the amplification stage, but what was previously poorly visible is amplified, i.e. ... the source of the noise is not so much the amplifier (although it also makes noise) as the matrix itself. The proof is to take an underexposed photo at ISO 100, and then in Photoshop, stretch the brightness several times - all the noise will be at a glance.

      • Neofot

        2 You need to find out about the stabilizers inside the camera from the specialists. I am sure that they are not there because the power does not come from the mains, but from the battery, which is stable (you wrote about this too). But this is if the battery is normal. And if poorly done, then short circuits occur between the cells, so the current strength and voltage can change dramatically (by milliseconds). After that, some pixels may remain on (noise) or off permanently (broken). In theory, this is very possible. I do not think that they only create noise, but they do too.
        7 We, apparently, have different things in mind. What you described I would not call noise. This is a weak background sound (sorry for the analogy).

        • Denis

          What kind of battery stability can we talk about if the difference between fully charged and fully discharged can be several volts? What other cell closures, what are you talking about?) Let's start with the fact that there are only two cells in the battery, and if any of them is closed (to the BMS board), then even an explosion is possible.
          And who said that all the elements of the camera circuitry work from 7 volts? Most logic circuits operate from 5 volts, respectively, without a stabilizer can not do in any case. Without stabilizers, unless electric motors can be powered without adjusting the speed, this is not a fact.

    • Gene jb

      I will try to answer an illiterate electrician a neophyte
      1. There is a cycle of articles on Habré - "gikporn". Flip through, see what semiconductors look like under a microscope. There are also matrices. It feels like a cow walked across the field and shit with nanometer cakes. If the precision of semiconductor fabrication were as precise to the atom as the purity, then you would get the perfect matrix. And so - they did not give it, they went too far there. And as a result, one cell brightens, the other darkens. The control then it passed, but after 2 days it died. And because of the inaccuracy of the PPs, the noise that is higher in the photo is obtained. On the SSD I think it will be a little better, but quite a bit.
      2. Do you think that the camera down took 4 volts from the battery and applied it to the matrix? Enlighten - the battery voltage is only on the power controller and the flash. Why on flash? Because it needs all the battery power. And the KP gives out 3.3v, 1.8v 1.2v, etc. Moreover, there can be many such identical voltages for different nodes. And aging occurs from the fact that some kind of stray alpha particle hit the path where the “atoms were not added” and the cell opened and did not close. Everything, finita la ...
      3. Well, firstly, not current, but voltage, and secondly, the higher the voltage, the more stable the circuit, because it is less susceptible to external noise.
      4. The edges of the matrix contacts. And they conduct heat better. From here, apparently increased noise.
      5. I will not argue, but some matrices are assembled from two. But it can be a layer of metal conductors and signal-outputting contacts.
      6. I do not use and do not know, but most likely not. I did not notice in the rabbi.
      7. Dead pixels and noise are easy to distinguish. And I already wrote - consumer goods are not for such exposure. Take medium format and film. There certainly won't be any pixels. And put up with the noise ...

  • Passer

    On my old 350d, already at iso100 and shutter speeds longer than 5sec, several blue and red assholes are visible, very bright and large. At ISO1600 and shutter speed of 30 seconds, they are already much brighter and more visible. These are really dead pixels, it's a pity there is no remapping. Everything that is smaller and dimmer, at slower shutter speeds, is not scary, it's hot.

  • Avdoshyn

    From my personal experience: I have a canon 350d, I remember taking once a photo of the street at night with a shutter speed of 30 seconds, at ISO 100. I already saw a couple of blue and red pixels on the computer. At first I thought that we were dead. Then I found out that pixels can also just heat up. In general, after that there were still photographs where these blue and red pixels also occasionally appeared. Let me remind you that for these photos the shutter speed was set to 30 seconds. I decided to conduct an experiment at my own peril and risk. I took a couple of photos of the starry sky with a shutter speed of ~ 40 minutes from ISO 100-200. I did not find any broken or hot pixels during a long study of the photo. Due to weather conditions, the photos were taken all in the summer, when at night the temperature is ~ 20 degrees.

  • Myhaylo kuharchuk

    Recently I was in the Chernobyl "zone", and noticed one joke - when the lens cover (Nikon D300s) is closed, a lot of spots appear at exposures of 10-30 seconds. After in Kiev, everything is in order for the same 10-30 seconds. And it came to gamma fries matrix pixels. Here's a dosimeter :)
    And I read it for a long time as I remember with Ken Rockwell, pin diodes, which shine with a peak at 880-920 nm, are on the matrix crystal connections, regardless of type to the gold conductors.

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