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Thread: Dead pixels ?

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    Dead pixels ?

    Brother went down to the lake lastnight to capture some lighting
    Rings me this morning asking if i can remove what he thought were dust bunnies.
    Upon closer inspection found these weird what looks like + scattered through out his images.

    Are these dead pixels? Shot with D70
    Posted screen shots, but if anyone wants a copy pm or email me.







    Simone

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    Yes, looks to be what I think. Are they present in every image ?
    Darren
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    Moderately Underexposed I @ M's Avatar
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    Simone, they look more like "hot" pixels to me. I think that if you google "D70 long exposure hot pixels" you will find that it is reasonably common. That is just going by memory and assuming that the shutter was open for a long exposure.
    Andrew
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    Moderately Underexposed I @ M's Avatar
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    I knew I remembered something.

    http://www.naturfotograf.com/D70_rev04.html

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    wouldnt a hot pixel be white?? or am i just assuming??

    M
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    Looks like hot pixels. Long exposures can really bring them out. My cameras remap pixels at the beginning of each month so maybe try changing the date on the camera forward to the following month and see if they go away.
    Cheers,
    Dave



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    Thanks guys

    Will pass that info on.
    Much appreciated

    Quote Originally Posted by kiwi View Post
    Yes, looks to be what I think. Are they present in every image ?
    Yes in all of lastnight shots

    Quote Originally Posted by I @ M View Post
    Simone, they look more like "hot" pixels to me. I think that if you google "D70 long exposure hot pixels" you will find that it is reasonably common. That is just going by memory and assuming that the shutter was open for a long exposure.
    Said exposure was between 30 sec & a minute. Thanks for link

    Dave ... will pass that tip on

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    A royal pain in the bum! arthurking83's Avatar
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    Quote Originally Posted by Charmed View Post
    .....
    Upon closer inspection found these weird what looks like + scattered through out his images.

    Are these dead pixels? Shot with D70....
    The cross shape is due to the 300% zoom factor too. ie. looking at each pixel 3x larger than it actually is. Best to do it at 100% zoom view. they should all then look more like proper pixels.

    Hot pixels will usually vary in position with every expsoure. if the pixels are always in the same place, then they're more likely to be dead pixels.. or a serious case of bad, or depending on your perspective.. GOOD luck

    best way to look for dead pixels is a shortish exposure with the body cap on or using the lens cap.
    Be aware though that some lens caps can leak some light(early Sigma 10-20mm's come to mind) at the edges.
    Anyhow, the resultant image needs to be totally black so that you can more clearly look for dead pixels. And they'll be either blue red or green.
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    Member redstocks's Avatar
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    I've never heard of dead or hot pixels! Does this sort of thing happen often, what causes it and can it be fixed?

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    Quote Originally Posted by arthurking83 View Post
    The cross shape is due to the 300% zoom factor too. ie. looking at each pixel 3x larger than it actually is. Best to do it at 100% zoom view. they should all then look more like proper pixels.

    Hot pixels will usually vary in position with every expsoure. if the pixels are always in the same place, then they're more likely to be dead pixels.. or a serious case of bad, or depending on your perspective.. GOOD luck

    best way to look for dead pixels is a shortish exposure with the body cap on or using the lens cap.
    Be aware though that some lens caps can leak some light(early Sigma 10-20mm's come to mind) at the edges.
    Anyhow, the resultant image needs to be totally black so that you can more clearly look for dead pixels. And they'll be either blue red or green.
    Still seeing cross shape here even @ 100% & in same place on other shots. Will get bro to do the lens cap exposure.




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    A royal pain in the bum! arthurking83's Avatar
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    Simone!!

    I gotta say too, some of them hot pixels look like dust bunnies too.

    Considering it's a D70, there's a very high probability that there's a mix of hot pixels and dust bunnies in there.

    i'm curious as to what aperture value your brother used.

    If very small(high f number) then the dust bunnies get a 'sharper' more defined look about them. and can look like dead pixels in the right(or wrong) conditions.
    get your brother to do a spot test too. blue sky small aperture doesn't even have to be focused.. all you need is a plain flat single tone background with a small aperture to make it easier to see the contrast in the spots.

    My D70s was notorious for these small dust spots, the D300 less so, probably because of the filter packs used now and the self cleaning sensor??

    does he or you have access to a copperhill sensor cleaning kit?(if not they're highly recommended)

    If they do turn out to be dust bunnies too, it's not recommended to 'blow' them out with a blower. These small dots types can be impossible to remove and may take up to three or more attempts to clean even with the copperhill kit.

    in the 100% crops the vast majority of the spots look like dust spots and there are two or three that look like hot pixels.
    looks like a bit of sharpening was used in the image too, whether USM in PP or in camera sharpening, it doesn't matter.. make sure there is no sharpening in the image to better assess what the issue could be.

    if there are any hot pixels, with each image the location of the affected pixels will change. dust bunnies never move until you move them or eliminate them ... or you can blur them with wider apertures or hide them in the shadows.
    Dead pixels don't move. Sometimes they 'miraculously' disappear.. and as Dave said some cameras have the ability to remap them(if not then they always stay put in the same spot)

    So he needs to check successive images taken both before and after.
    Shouldn't matter when they were taken, only that they are the shots taken before or after.


    I think there's nothing to worry about.... other than getting the copperhill sensor cleaning kit!
    Share it between yourselves if you have too, it goes a a long way.

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    Hey ak

    Thanks for all that, will get him to go through it all when he comes around today.
    Started yday arvo, but things got a bit hectic here.

    Keep you posted

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