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    gerainte1
    gerainte1 e2 Member gerainte1 vcard United Kingdom
    25 Jul 2014 - 10:24 PM

    Hello,

    i took a long exposure recently and the image is absolutely covered in hot pixels. I have read that every camera develops a few ( don't know if this is true) but my image has almost complete coverage. What does this mean and is my camera OK? I have a Nikon D3100 had it for a year.

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    lobsterboy
    lobsterboy Site Moderator 1014152 forum postslobsterboy vcard United Kingdom13 Constructive Critique Points
    25 Jul 2014 - 10:28 PM

    Are you sure it is not just noise? What ISO were you using ?
    Can you post up an example ?

    gerainte1
    gerainte1 e2 Member gerainte1 vcard United Kingdom
    25 Jul 2014 - 10:32 PM

    Hi may be, I'll up load the image .

    gerainte1
    gerainte1 e2 Member gerainte1 vcard United Kingdom
    25 Jul 2014 - 10:35 PM

    I can't upload another image today, thanks for getting back and i will post it tomorrow.

    Chris_L
    Chris_L e2 Member 1042 forum postsChris_L vcard United Kingdom
    25 Jul 2014 - 10:38 PM

    You'll get more this time of year due to the higher temperature, more the higher the iso, more the longer the exposure, more caused by interference from cell-phones and you can get even more if you don't have some kind of long-exposure NR turned on in camera (depends on model).

    sherlob
    sherlob e2 Member 82332 forum postssherlob vcard United Kingdom125 Constructive Critique Points
    25 Jul 2014 - 11:00 PM

    Personally I think in camera long exposure NR isn't worth the hassle. I agree that the problems sounds like it is coming from heat related noise rather than 'hot pixels' which is typically the name we give to a defective pixel. Do you get the same pixels causing a problem in shorter handheld exposures? Say 1/60th sec? If not, the problem is noise.

    On a side issue. I think at time some photographers attempt to go for a longer exposure than is strictly needed for the effect they want to create. E.g. you don't need an exposure of 10 minutes to get smooth water. Similarly, star trials are easier to capture using a series of 30 second exposures that are then stacked. What are using the long exposure for? And does it need to be as long as you are using it for?

    gerainte1
    gerainte1 e2 Member gerainte1 vcard United Kingdom
    26 Jul 2014 - 8:19 AM

    Hi
    I have uploaded the photo to my and put critique on it. The ISO was 100.

    It was really warm.

    Sherlob, you've hit a nail on the head with why was i doing it, as I don't know . it was an experiment to see if I could capture some movement in the clouds but they didn't really move either so a long lesson.

    Geraint

    Chris_L
    Chris_L e2 Member 1042 forum postsChris_L vcard United Kingdom
    26 Jul 2014 - 2:31 PM

    As this photo-sharing site hasn't embraced the year 2014 I think the image is too small for me to spot them.

    If you were able to crop the shot, then post it here in this thread that would help or upload it to a website that allows the full image and put a link.

    gerainte1
    gerainte1 e2 Member gerainte1 vcard United Kingdom
    26 Jul 2014 - 11:42 PM

    Hi John I'll post of flicker
    [url=https://flic.kr/p/otkLDV][img]https://farm4.staticflickr.com/3905/14749251631_17658fc437_c.jpg[/img]

    gerainte1
    gerainte1 e2 Member gerainte1 vcard United Kingdom
    26 Jul 2014 - 11:43 PM

    Hi John I'll post of flicker
    her's the link
    https://www.flickr.com/photos/126232476@N06/14749251631/

    Chris_L
    Chris_L e2 Member 1042 forum postsChris_L vcard United Kingdom
    27 Jul 2014 - 1:39 AM

    Gerainte, downloaded the 3000 px one and viewed it 1 to 1

    I don't think you have anything to worry about.

    It totally looks like temporary hot pixels, there's the odd blue one, the rest mainly yellowish. I've seen it before, it's the kind of noise that you get from a long exposure in hot weather, it's different from high iso noise as it only affects a few pixels.

    It's not the same as a permanent hot pixel. (Even those aren't the end of the world as they can be mapped out with software actions etc).

    Do a test with your camera, a series of shorter exposures with the lens cap on, if there's a fault you'll see it.

    gerainte1
    gerainte1 e2 Member gerainte1 vcard United Kingdom
    27 Jul 2014 - 10:04 AM

    Thank you for taking the time and effort to have a look and post this comment. That's a relief, the camera was OK yesterday, and I'll do what you suggest with the lens cap on to check further. Thanks again.
    Geraint

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