some questions about sensor dust

Discussion in 'Digital Discussion & Q&A' started by ernie, Nov 13, 2009.

  1. ernie

    ernie TPF Noob!

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    hello,

    been traveling for a few months now and with the changing lenses now and again, i'm afraid i have some dust in my camera. just wanted to stop by here and ask a few questions before i do anything.

    how do you recognize sensor dust exactly? i read somewhere you cannot see it through the viewfinder, only in the pictures themselves. however, the stuff i see is through the viewfinder, can't see anything in the pictures themselves (that is after taking a shot of a white wall and zooming in (on the camera display) where the spot is supposed to be - nothing). i have cleaned lenses and the little viewfinder, no effect. does this mean it's on the mirror itself? if yes, how would i go about cleaning this? can i do it myself with a clean sort of cloth, just like you do with the front of lenses?

    and do i even have to clean it? since it doesn't seem to have an effect on the actual pictures i'd rather not touch it, altough i haven't watched them on a big screen yet, only on the little camera display. i guess i could go to a repair shop and ask them to clean everything (to be sure) but i'm in china now and i don't have much faith in the local electronics-guys, with the fake equipment and all.

    thanks,
    ernie
     
  2. rocdoc

    rocdoc TPF Noob!

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    Ernie,
    Look this up, there is some info posted out there. DO NOT GO WITH A CLOTH INSIDE YOUR CAMERA!!!
    First off, to see if there is dust on your sensor, take a bunch of shots at the smallest aperture your lens allows (f/22 or f/32 or whatever you have). Take shots of something like a blank wall or ideally a smooth neutral surface. View them at 100% on your monitor, and specs of dust would show up as dark irregular things.
    If you find that is the case, read up on the proper cleaning procedure, and do not go into the camera until you are comfortable. The first step would be to lock up the mirror and give a couple of solid puffs with a "rocket" or similar device. If that does not work, you would have to swab it. photosol.com sells some supplies and have videos on their site on the how-to's. Search "sensor cleaning" in the forums here and on sites like dpreview. You must NEVER touch the mirror, like you say. The procedure is pretty well defined, involves locking up the mirror and swabbing the sensor, if you do the homework and you find a dust-free environment (for me: the bathroom) it's not as scary as it sounds, but if you are more comfortable just ask the pros to do it (it will cost $).
     
  3. Dwig

    Dwig TPF Noob!

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    That's because of the basic nature of an SLR (Single Lens Reflex) camera. The mirror reflects the image from the camera lens onto a viewing/focusing screen to provide the image you see in the VF. When you take the picture, the mirror moves out of the way so the image from the lens can be projected onto the sensor/film. The actual shutter lies just in front of the sensor/film and behind the mirror. As a result, the dust and specs you see in the VF are those that are on the viewing/focusing screen which can't influence the final image. Dust on the sensor can't be seen in the VF since you are seeing an image from the sensor when looking through the VF.

    Sensor dust isn't actually on the sensor itself. Its on a cover filter mounted just in front of the sensor. As a result, sensor dust usually shows a bit of a blurry out-of-focus-like edge. When shooting at very wide apertures, the smaller dust specks blur so much you won't see them. They become visible, or more visible, as you stop the lens down to smaller apertures.
     
  4. Eco

    Eco TPF Noob!

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    If you are scared to do it on your own check with your local camera store. I had one of my cameras cleaned a couple months ago and was charged $70 (+/- forget exactly). The took a before and after picture of the sky to show all of the dust before and none after.

    At some point I'll grow a set and learn to do it on my own.
     
  5. ernie

    ernie TPF Noob!

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    thanks for the info everyone. can't really check for sensor dust nor clean it since i don't have the equipment with me here, so i will leave it as it is right now. if i do have some dust on the sensor i'll photoshop it out when i get home, it's not worth the risk or trouble of damaging my camera. might get it cleaned (just to be sure) in japan, those guys invented nikon so they should know i guess :)

    thanks again!
     
  6. Garbz

    Garbz No longer a newbie, moving up!

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    Checking for sensor dust is trivial. Set you aperture as small as it will go, and take an out of focus shot of something plain like a piece of paper or the ceiling. Dust will show up at the smallest aperture as a completely black spot.
     

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