Hot Pixels


Two nights ago was full moon. I looked out the window and there it was, bright and round, and illuminating the edges of the clouds surrounding it. What a nice sight, I thought, and snapped a few shots just as the clouds started to obscure it. When I downloaded the images and viewed them all at full size, I found some bright dots which I initially thought were stars. However, the same dots appeared in all the other images as well ? same colour, same spot. A search with Google revealed that these are hot pixels.

Hot pixels are those that appear as bright dots in the image in long exposure, especially in low light and night shots. The CCD, which captures the image, consists of millions of light sensitive elements. Hot pixels usually occur when the CCD is heated up after prolonged use, resulting in charge leakage in some of the sensors. This makes the particular pixel brighter than the surrounding ones and shows up as white, red or green dots in an otherwise dark background.

Most if not all digital cameras have hot pixels. This anomaly can be removed by remapping the CCD. Remapping simply hides the odd pixels by masking it with the colours of the adjacent pixels. The camera has to be sent back to the manufacturer to be remapped. It can also be reduced by using the noise reduction feature available in most digital cameras. For the moment, I can live with those odd dots which appear only in images taken with slower shutter speeds. These defects are nothing that photo editing software cannot correct.

Apart from hot pixels, the CCD is also plagued with stuck pixels and dead pixels. In stuck pixels, the particular sensor is always on, producing a bright dot irrespective of shutter speed and aperture size. This usually appear as red, green or blue in the image. Dead pixels appear as black dots because the sensor is always off, thus not registering any light. This normally turn up as black dots in images taken in bright condition.

The LCD screens are also afflicted by these defects. This is unavoidable because the elements weaken as they age and start to malfunction. I have no complaints regarding this problem as this Nikon Coolpix 3100 has served me well, having captured over two thousand images and is still doing fine generally. The only gripe I have is that the battery power is exhausted fairly quickly and I usually have to carry a few set of spares every time I go out on a shooting spree.

Author: Peter Tan

Peter Gabriel Tan. Penangite residing in the Klang Valley. Blissfully married to Wuan. A LaSallian through and through. Minion to three cats. Wheelchair user since 1984. Columnist of Breaking Barriers with The Borneo Post. Principal Trainer at Peter Tan Training specialising in Disability Equality Training. This blog chronicles my life, thoughts and opinions. Connect with me on Twitter and Facebook.

13 thoughts on “Hot Pixels”

  1. A bit too much technical jargon here for me to understand but damn, I wished I had a digicam! Contributions, anyone? 😀

  2. You will understand when you have used a digicam long enough and discover those annoying little dots in all your images.

  3. Peter

    I luv the pic 🙂
    Why because i luv 2 sketch n draw fantasy and spiritual images ,so the moon n clouds are almost always in the background.Your pic is one of the best images ive seen in a long time.
    Thanks 4 sharing it 🙂
    tcz

  4. didn’t understand a word you were saying 😉 but the picture though is beautiful.
    thanks for dropping by my blog, man! cheers!

  5. Sashi,
    My writing is that difficult to understand huh? But I am glad you found the picture interesting. Have a nice day.

  6. Peter
    Thanks to you and the pic, i was inspired to pick up my pencil and finish a rather large canvas.
    Until today i hadn’t sketched or painted n e thing for a month .
    Thanks again 🙂
    tcz

  7. Sweetspirit,
    You are welcome, again. It has been a long time since I have used a pencil to sketch anything. I used to like still-life and portraits. Now you have stirred that in me again. I should thank you, too.

  8. Question – Why did the chicken cross the road?

    Kindergarten teacher:
    To get to the other side.

    Aristotle:
    It is the nature of chickens to cross roads.

    Ronald Reagan:
    I forget.

    Arthur Andersen consultant:
    Deregulation of the chicken’s side of the road was threatening its dominant
    market position. The chicken was faced with significant challenges to create and
    develop the competences required for the newly competitive market. Andersen, in
    a partnering relationship with the client, helped the chicken by rethinking its
    physical distribution strategy and implementation processes. Using the Poultry
    Integration Model (PIM), Andersen helped the chicken use its skills,
    methodologies, knowledge, capital and experiences to align the chicken people,
    processes and technology in support of its overall strategy within a Program
    Management framework.

    Richard M. Nixon:
    The chicken did not cross the road. I repeat, the chicken did NOT cross the
    road.

    Computer Programmer:
    In order for the chicken to cross the road safely they not only need one driver
    to access the server farm if not they will hang in the middle of the road.

    Jerry Seinfeld:
    Why does anyone cross a road? I mean, why doesn’t anyone ever think to ask,
    “What the heck was this chicken doing walking around all over the place,
    anyway?”

    Bill Gates:
    I have just released the new Chicken Office 2000, which will not only cross
    roads, but will lay eggs, file your important documents, and balance your
    checkbook.

    Dr M:
    You know, I am tired of all this…’apa-nama’ chicken-chicken bisnes…the
    foreign powers should stop intervening in our domestic affairs and just leave
    our chickens alone…. if they want to… ‘apa nama’ cross the road, they should
    be allowed to cross the road… Malaysia is a democratic country, we let our
    chickens do whatever they want to do… as long as they don’t threaten the Malay
    unity and try to topple the government…and if they plan to do so… we won’t
    hesitate to use the ISA…

    Pak Lah:
    Ini semua adalah khabar angin sahaja…jangan percaya khabar – khabar angin ini
    semua… biasalah ini adalah taktik pembangkang untuk memecah
    belahkan perpaduan ayam-ayam semua… jangan percaya… jangan percaya….

    Sammy Vellu:
    ayyooyoo… belakang cerita lain kali, kita sude bikin banyak jembatan, itu
    ayam musti guna jembatan untu lintas itu jalan lagi pun kalu itu ayam mau pigi
    jalan-jalan, beritau sama saya juga, saya bolley buat lebbey banyak toll……..

    Karam Singh Valia:
    Seperti yang saudara dapat lihat, kelihatan ayam-ayam itu sedang melintas
    jalan, mereka bukan sahaja melintas jalan malah membuang najis di atas jalan dan
    ini adalah pencemaran Yang paling hebat di maya pada ini. Bapa-bapa dan ibu-ibu
    ayam haruslah mengambil inisiatif untuk melatih ayam-ayam agar menahan najis
    sewaktu melintas jalan, sekian saya sudahi dengan……… Ayam di jalan di
    lintaskan Ayam di reban mati tak makan

    Colonel Sanders:
    I missed one?

    Bill Clinton:
    I’ve had so many chicks, I can’t remember…

    ANOTHER question:
    Why take a photo of the moon?

  9. Heyy

    Peter, I was at the penang bloggers meetup thingy yesterday, and Lucia was mentioning your name and all, so I here I am at your page. Just wanted to say hello. The blog meetup isnt exactly one might say ‘receptive’, just me and Lucia. Aha but im glad to have made a new friend and maybe next time, with due notice, you can come along 🙂
    Like your pics and it was nice knowing about the pixel thingies. The batteries- it happens, when you the recharge cycles go up the performance goes down, though it was said tha li-on batts can tahan this stuff..
    Cheers
    jasdev

  10. Hey Jasdev,
    Perhaps we will see more people attending at the next meet. Keep blogging. 😀

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