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Old Feb 14, 2010, 3:13 AM   #1
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Default A Problem With Dots

Okay, this will be the third digital camera that I have encountered this problem. Darker dot or dots in the sky. My friends Nikon D40x would usually have 2-3 darker little uniformed dots in the sky, however this only happened when the sky was part of the photograph and it was random.

My Fuji S9000 always had 1 small dark dot in the sky. When I mean dark, the dot was about 2 f-stops darker then the rest of the sky. Healing brush or clone tool always cured that.

A customer returned a Panny P&S complaining of 2 dark dots in all of her photographs that had skies in them. Ran a few test shots and sure enough they were there.

This is not a dust problem. My gut reaction was that something in the lens created the dot or dots. Swapping out the lens on the D40x threw that theory out the window. The dots were still there.

The only conclusion that I can come up with, is that it is a sensor problem. Does anyone else have a dot problem? Any solutions?
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Old Feb 14, 2010, 3:25 AM   #2
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Dots in the sky can be caused by a number of different problems. Dust on the lens or the sensor, as well as problems with the sensor cna result in dots. Swapping the lenses on the D40X doesn't mean your S9000 didn't have dust in the lens.

On a P&S, there's no other option except to return the camera for servicing, but for a dSLR, there's a lot of different maintenance procedures the user can take.
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Old Feb 14, 2010, 6:59 AM   #3
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Why have you ruled out dust as the problem? Dust is a common problem, especially in DSLR's. Skies are the most common place that dust show's up, as it is bright, light in color and typically shot with smaller apertures. I doubt it's a lens problem as even small scratches don't affect picture quality. It would take something fairly large on the lens to cause a problem like this, and likely be able to see it. Also, if it were a sensor issue, I think the problems would be apparent in all your images. Finally, since the problem has shown up in 3 cameras, I doubt that you have gotten 3 bad sensors in a row.
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Old Feb 14, 2010, 11:13 AM   #4
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Dust is not the issue. My friends D40x was brand new. I was the one that took the camera out of the box and attached the lens. The first shot with a sky had the dots. Dust can take on a variety of shapes and patterns and this was not dust. Since the S9000 and Panny are fixed lens, dust would not be on the sensor. Now I bought the S9000 used, but before I shot with it, the camera was cleaned. That includes taking off the front lens cap and blowing it with air. This procedure is done to all my cameras after I shoot. As far as the customers Panny, the camera was only a week old. As we all know the lens is only exposed (for that type of camera)when the camera is powered on.

I once had an old Rolli TLR. This camera had a similar problem. It sat around for a year without being used. My father gave it to me and I started seeing dark dots in the sky area of the photograph. When you really looked at the lens, you could see lubricants leaking along the iris diaphragm. When the shutter was tripped I guess it created a little spraying effect.

That was my initial thought when I first encountered this problem with the Nikon D40X. I have seen cameras sit on the shelves for over a year in my store before being sold. Like I said before, I swapped the kit lens on the D40X with another new lens my friend bought for this camera and it still had the same problem.
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Old Feb 14, 2010, 11:54 AM   #5
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Zoom lenses can act as bellows, sucking in air and associated foreign substances as you zoom or, in the case of a P&S digicam, just when you turn the camera on. If the problem occurs in a P&S digicam, there's no alternative but to send it in for service. If the problem occurs in a dSLR, it could be a foreign substance on the image sensor, between the image sensor and the lens, or in the lens between any of the lens groups. The possiblity of it being a flaw in the image sensor or the in-camera processing is slight, as evidenced by your own experience with a Rolleiflex TLR.
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Old Feb 14, 2010, 1:01 PM   #6
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Spots which show up in the same place, especially in areas of sky or large, light colored surfaces, are usually dust particles on the sensor surface. To get them to really stand out, use the smallest aperture (f/16 or smaller) and take a shot of clear blue sky. As TCav mentions, zoom lenses on digicams move air in and out when they are zoomed. Over time, something inevitably gets past the seals, or the seals themselves break down and lose a piece or two which ends up on the sensor.
You need good light and good eyes to spot small particles on a camera sensor, so a quick look won't necessarily reveal anything. I have had to go through several iterations of cleaning and testing before being satisfied.

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Old Feb 14, 2010, 1:42 PM   #7
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Quote:
Originally Posted by Ancientritual View Post
Dust is not the issue. My friends D40x was brand new. I was the one that took the camera out of the box and attached the lens. The first shot with a sky had the dots.
Err, what does "brand new" have to do with the question? Every dSLR I've ever bought had dust when it was brand new...

Have you even tried cleaning the sensor?

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Old Feb 14, 2010, 1:44 PM   #8
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You need good light and good eyes to spot small particles on a camera sensor, so a quick look won't necessarily reveal anything. I have had to go through several iterations of cleaning and testing before being satisfied.

brian
I've only seen a dust particle once, and that was hair from my dog which covered a quarter of the lenth...

With my D1x, (which attracted dust like some creature from a horror movie) I still couldn't see One particle - But I sure was able to clean it.

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Old Feb 14, 2010, 2:25 PM   #9
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Quote:
Originally Posted by Ancientritual View Post
Dust is not the issue. My friends D40x was brand new. I was the one that took the camera out of the box and attached the lens. The first shot with a sky had the dots. Dust can take on a variety of shapes and patterns and this was not dust. Since the S9000 and Panny are fixed lens, dust would not be on the sensor. Now I bought the S9000 used, but before I shot with it, the camera was cleaned. That includes taking off the front lens cap and blowing it with air. This procedure is done to all my cameras after I shoot. As far as the customers Panny, the camera was only a week old. As we all know the lens is only exposed (for that type of camera)when the camera is powered on.

That was my initial thought when I first encountered this problem with the Nikon D40X. I have seen cameras sit on the shelves for over a year in my store before being sold. Like I said before, I swapped the kit lens on the D40X with another new lens my friend bought for this camera and it still had the same problem.
Dust eventually becomes an issue even with point and shoot cameras. I've seen and heard of cameras coming out of the box with dust. As TC said, zooming in and out, the lens can act as a bellows sucking dust in. With the small sensors, and large DOF of a P&S, dust will show up quite easily. If the spots show up in the same part of the frame in each image, I can almost guarantee dust is the issue. Defective sensors tend to show their issues has hot or stuck pixels which don't look anything like dust. And again, though it is possible, dust inside the lens likely won't show up in any images. I would take a series of images of the sky (or a white piece of paper) at various apertures. If the spots aren't apparent at larger apertures and then show up in smaller apertures in the same spots, dust is your issue. For the D40x, try using a rocket blower first, then try cleaning the sensor with an appropriate method. For the P&S, you'll have to send them in for service.
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Old Feb 15, 2010, 12:30 AM   #10
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The dust theory for the S9000 might be valid. For the D40X and Panny this is not the case. The sensor was blown out several times and inspected before changing lens on the D40X . I have been involved in photography for 35 years, so cleaning cameras and being aware of dust problems is pretty much second nature to me. The Panny was brand new. When a customer buys a camera from us, we open the box and make sure everything is in there, and we look at the camera to make sure there are no defects. A new Panny is in a protective thin foam envelope, so dust would have a hard time creeping in there. Seals will not break on a week old camera unless they were defective, but still it would take some time for the dust to work itself onto a sensor in a P&S.
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