Sensor Problem?

Discussion in 'Beyond the Basics' started by CanAm, Mar 6, 2008.

  1. CanAm

    CanAm TPF Noob!

    Joined:
    Mar 4, 2008
    Messages:
    113
    Likes Received:
    0
    Location:
    San Jose, CA
    Can others edit my Photos:
    Photos NOT OK to edit
    So, I was screwing around, taking pictures of the ember on the end of an incense stick, and I noticed these bright splotches of light here and there in the pictures. I thought it was strange and set a 30 second exposure with the lens cap on and took a pic, and I got the same result.

    Whats the issue here? Does my sensor need a cleaning, or what?

    http://i16.photobucket.com/albums/b35/airsoftsilent/IMG_0449.jpg

    http://i16.photobucket.com/albums/b35/airsoftsilent/IMG_0456.jpg

    EDIT- being told by a friend that it's just pixel noise from lack of light. Can someone verify this?
     
  2. LaFoto

    LaFoto Just Corinna in real life Staff Member Supporting Member

    Joined:
    Feb 1, 2004
    Messages:
    34,814
    Likes Received:
    814
    Location:
    Lower Saxony, Germany
    Can others edit my Photos:
    Photos NOT OK to edit
    I must ask others further: are those the dreaded "dead pixels" then? If they show like this in a photo taken with the lens cap on? But why would they be in red and blue colour?
     
  3. Flash Harry

    Flash Harry TPF Noob!

    Joined:
    Jun 26, 2006
    Messages:
    1,918
    Likes Received:
    1
    Location:
    Durham, UK
    Can others edit my Photos:
    Photos NOT OK to edit
    RGB, think about it. H
     
  4. Garbz

    Garbz No longer a newbie, moving up!

    Joined:
    Oct 26, 2003
    Messages:
    9,713
    Likes Received:
    203
    Location:
    Brisbane, Australia
    Can others edit my Photos:
    Photos NOT OK to edit
    Indeed they are in logical groups (RGBG). They die white if all 4 in a group fail which happens often.

    There are 2 half truths here. Yes it's noise, and yes it's a dead pixel. But it's not permanently dead. Pixels will give up in a predictable way as the exposure length increases. Be thankful you have so few at 30 seconds.

    The fact that they die predictably is a good thing. Long exposure noise reduction is a system available in most cameras whereby the camera clears the sensor after exposure, takes another exposure without opening the shutter, and then does a pixelwise subtraction of the two images. Since the death of a pixels is predictable given the exposure all the specs should be reduced.
     
  5. Battou

    Battou No longer a newbie, moving up!

    Joined:
    May 10, 2007
    Messages:
    7,997
    Likes Received:
    26
    Location:
    Slapamonkey, New York
    Can others edit my Photos:
    Photos NOT OK to edit
    Is that what my digital is doing when I use it for long exposures....I takes the image and then acts like it is taking another one directly after it, the number of repetes varies with duration.

    This is an odd thought to me as I did not understand what was happening, this explanation makes perfect sence except for one thing, the particular camera, Kodak sacrificed a ton of features and took a handfull of shortcuts in development of my digital camera and it seems unlikely that it would have any noise reduction at all.

    Sorry I don't mean to hijack this, but I am very curious.
     
  6. CanAm

    CanAm TPF Noob!

    Joined:
    Mar 4, 2008
    Messages:
    113
    Likes Received:
    0
    Location:
    San Jose, CA
    Can others edit my Photos:
    Photos NOT OK to edit
    So in other words, I have nothing to worry about, correct?

    Will this affect daytime shooting at all?
     
  7. RyanLilly

    RyanLilly No longer a newbie, moving up!

    Joined:
    Aug 27, 2007
    Messages:
    1,478
    Likes Received:
    8
    Location:
    St. Louis, Missouri, USofA
    Can others edit my Photos:
    Photos NOT OK to edit
    It probably won't affect daytime shooting, but it will probably also be worse at higher ISO with long exposures. This is normal behavior for sensors during long exposure times, newer sensors seem to do a better job,or just have better NR, but I don't think that you have a problem. Take a few shots at ISO 100, with the lens cap on, at different shutter speeds; you probably won't see the hot pixels, and I you don't see them in normal shots, than don't worry about it. And If you really need tho feel better about it, I can post some long exposures from my Olympus E-10; It has HORRIFIC hot pixels.;)

    Ryan
     
  8. Garbz

    Garbz No longer a newbie, moving up!

    Joined:
    Oct 26, 2003
    Messages:
    9,713
    Likes Received:
    203
    Location:
    Brisbane, Australia
    Can others edit my Photos:
    Photos NOT OK to edit
    Correct and no it shouldn't. If it does it during a fast exposure you really do have a stuck pixel. This is definitely not unheard of.

    Easy way to find out. If the processing takes just as long as the exposure then that's what it's doing. Take a 4 second picture and find out. Shortcuts are feature shortcuts, often requested by some numbnuts in a marketing department. Noise reduction is a VERY marketable feature. It would take a special kind of person to omit this feature from a camera :er:
     

Share This Page