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Author Topic: Is This Sensor Dirt?  (Read 4135 times)

Rob C

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Is This Sensor Dirt?
« on: January 21, 2011, 03:26:00 pm »

This is a 100% blowup from a D700 file.

I'm pretty sure there were no aliens out there in the evening, but as surely, I'm not sure what this mark is.

The lens wasn't changed outdoors, and I was very careful to avoid draughts etc. when I did fit it to the camera. As this is the first time I've come across possible sensor dirt, I'm not sure that I can recognize it when it happens. I'd have imagined it to be a sharp edged thing, more like dust on negatives, for example.

Maybe somebody can tell me what it really is? No, I wouldn't be looking down into the throat of the camera when the lens was being put in place, and I certainly would take care not to sneeze!

Help!

Rob C

langier

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Re: Is This Sensor Dirt?
« Reply #1 on: January 21, 2011, 03:40:21 pm »

Yep. A speck of dust on the AA filter on the front of the sensor. It's still simply a fact of life and easy to fix in ACR and software of your best images.

From experience, you will definitely find this in the sky and be thankful it's a single little dot.

You pull the battery, turn off the camera, change lenses in the car/house, and no matter what, you will still get little spots like this. It's a little annoying like a piece of fuzz on the film gate of your film cameras and you can spend a lot having the sensor cleaned by a pro, learn to do it yourself, or not worry too much about it and continue to shoot.

Though my recent crop of Nikon cameras (300, 300s, 700) has the sensor cleaner, I still get these spots, though not as many times as I once did. I don't go out of my way when changing lenses, other than not to spit or sneeze inside the body. One time I simply blew-off the sensor and instead managed to spit...those spot still haunt me and take a lot of work to clean, even using ACR and applying the spot removal settings.

It isn't the end of the world and IMO, if I have six or less that I can see on the frame, I figure it's good enough!

Besides not spitting on the sensor like me, you can minimize the appearance of these artifacts by using your lenses at f/5.6 or wider (higher res and image quality on most pro Nikon lenses anyway), handling it on your edited and best images when you process (less time than a wet cleaning), and learning how to *carefully* clean your sensor when you get a few more spots (http://www.cleaningdigitalcameras.com/).

Last year, I shot six different cameras and nearly 80,000 images predominately on my Nikon herd. Though there is dust in the sky of many, most seems confined to areas with other than sky.

Moral of the story, don't sweat it, simply be aware of it and keep shooting!
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ErikKaffehr

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Re: Is This Sensor Dirt?
« Reply #2 on: January 21, 2011, 03:50:14 pm »

Hi,

Looks like dust to me. Try to clean the sensor...

http://www.lensrentals.com/news/2010.04.02/how-to-clean-a-camera-sensor

I use "Visible Dust" myself.

Best regards
Erik

This is a 100% blowup from a D700 file.

I'm pretty sure there were no aliens out there in the evening, but as surely, I'm not sure what this mark is.

The lens wasn't changed outdoors, and I was very careful to avoid draughts etc. when I did fit it to the camera. As this is the first time I've come across possible sensor dirt, I'm not sure that I can recognize it when it happens. I'd have imagined it to be a sharp edged thing, more like dust on negatives, for example.

Maybe somebody can tell me what it really is? No, I wouldn't be looking down into the throat of the camera when the lens was being put in place, and I certainly would take care not to sneeze!

Help!

Rob C
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NikoJorj

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Re: Is This Sensor Dirt?
« Reply #3 on: January 21, 2011, 04:31:57 pm »

I'm pretty sure there were no aliens out there in the evening, [...]
Seems like at least 3 people here are part of a worldwide conspiration to cover "them", uh?

Anyway, that definitely looks like an UFO trying hopelessly to disguise himself into a dust speck on sensor. Nice try, haha!
If you want to make "them" feel a bit safer you could read this on dry sensor cleaning (easy and safe).
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Rob C

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Re: Is This Sensor Dirt?
« Reply #4 on: January 21, 2011, 04:59:10 pm »

Thanks for the replies, guys.

I never ever found anything like this on the D200 - the D700 is much newer - and I never did use the shaking element thing to dislodge any dust. However, since finding these marks, I have selected the option for a shake before and after shooting, so I shall see if it improves things next time I go out... hope it doesn't just wake up stuff lying at the bottom of the well!

The stuff shown in the link (the building with black marks) is what I'd imagined dust on the sensor would look like, just like stuff on a negative or tranny, not a soft 'alien' thing like this on the files.

Oh well, I guess I shall live with it if it doesn't get much worse; I don't feel inclined to send anything away for treatment, because if even the manufacturers can't deliver stuff without dust in it...

Thanks again,

Rob C

Paul Sumi

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Re: Is This Sensor Dirt?
« Reply #5 on: January 21, 2011, 08:08:30 pm »

The stuff shown in the link (the building with black marks) is what I'd imagined dust on the sensor would look like, just like stuff on a negative or tranny, not a soft 'alien' thing like this on the files.

How dust appears on your image file depends on the f/stop used to make the exposure.  At f/2.8 you probably won't see anything.  As you stop the lens down any dust particles become more visible, the same way stopping down a lens increases DOF.

Paul
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ErikKaffehr

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Re: Is This Sensor Dirt?
« Reply #6 on: January 22, 2011, 02:04:58 am »

Hi,

I clean the sensor probably once a week when on travel, using Visible Dust Artic Butterfly. It's just a minutes work.

Dust doesn't get on sensor when changing lenses. The dust in the mirror chamber is bouncing around because of mirror flipping up and down and the focal plane shutter is open during exposure. Keeping the mirror chamber clean is a very good idea, so being careful with changing lens is not a bad idea.

Best regards
Erik


Thanks for the replies, guys.

I never ever found anything like this on the D200 - the D700 is much newer - and I never did use the shaking element thing to dislodge any dust. However, since finding these marks, I have selected the option for a shake before and after shooting, so I shall see if it improves things next time I go out... hope it doesn't just wake up stuff lying at the bottom of the well!

The stuff shown in the link (the building with black marks) is what I'd imagined dust on the sensor would look like, just like stuff on a negative or tranny, not a soft 'alien' thing like this on the files.

Oh well, I guess I shall live with it if it doesn't get much worse; I don't feel inclined to send anything away for treatment, because if even the manufacturers can't deliver stuff without dust in it...

Thanks again,

Rob C
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Alan Goldhammer

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Re: Is This Sensor Dirt?
« Reply #7 on: January 22, 2011, 08:08:38 am »


I never ever found anything like this on the D200 - the D700 is much newer - and I never did use the shaking element thing to dislodge any dust. However, since finding these marks, I have selected the option for a shake before and after shooting, so I shall see if it improves things next time I go out... hope it doesn't just wake up stuff lying at the bottom of the well!

Rob C
Rob,
I think there is some adhesive at the bottom to catch dust following sensor shake.  I have a D300 and have the camera set to do the sensor clean every time the camera is turned on.  It seems to perform quite well.

Alan
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langier

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Re: Is This Sensor Dirt?
« Reply #8 on: January 22, 2011, 09:07:56 pm »

I believe you are right, Allen. I think it says to keep the camera level when you turn it on for the auto dust-shaking and I think you have several option, manual, when you turn it on, when you turn it off and maybe at both ends, but I may be confusing this with my 5D2.

In any case, dust seems to be less a problem with the D300-D700 than it did with my D100, D200, and D2x/s bodies.

I know I've cleaned each using a wet method a couple of times, but seldom need to as frequently as just a few years ago.
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Ken Bennett

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Re: Is This Sensor Dirt?
« Reply #9 on: January 23, 2011, 09:12:43 am »

Dust has been less of a problem with my newer cameras, but I still get the occasional spot that won't come off with the auto-shaking.

You can check your sensor by setting a very small aperture and aiming the camera at a smooth wall. I do this in my studio. Yes, the shutter speed tends to be in the 4-second range, but that doesn't matter for this test -- in fact it probably helps, since you want to avoid any sharp subject matter in the photo. You can also shoot the clear blue sky at f/22 or so. Dust spots will show up very clearly -- and I'll bet that you're surprised at how many you have that you never noticed.
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walter.sk

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Re: Is This Sensor Dirt?
« Reply #10 on: January 24, 2011, 10:59:15 am »

How dust appears on your image file depends on the f/stop used to make the exposure.  At f/2.8 you probably won't see anything.  As you stop the lens down any dust particles become more visible, the same way stopping down a lens increases DOF.

Paul
Yes, the dust spots are more evident at small apertures. This raises a question for me, though.  I used to think that they became more visible at small apertures because of increased depth of field, until I was informed by somebody, probably on these forums, that depth of field had nothing to do with the increased visibility of the spots.  It had to do with some other phenomenon, maybe with the angle of light coming through a smaller aperture, but I can't remember.  Nor has a search here done any good.  I do remember that the explanation showed pretty definitively that it could not be depth of field that affects the visibility of the dirt.

So, if somebody knows why, please tell me again.
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NikoJorj

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Re: Is This Sensor Dirt?
« Reply #11 on: January 24, 2011, 11:53:17 am »

I do remember that the explanation showed pretty definitively that it could not be depth of field that affects the visibility of the dirt.
I'd say that the extended depth fo field on sensor side (has a separate name in french = profondeur de foyer, but I don't know if it's the same in english as it's basically the same) does mean that light rays arrive more focused, ie more parallel, and call it a wash. ;)
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Rob C

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Re: Is This Sensor Dirt?
« Reply #12 on: January 24, 2011, 02:47:45 pm »

I'd say that the extended depth fo field on sensor side (has a separate name in french = profondeur de foyer, but I don't know if it's the same in english as it's basically the same) does mean that light rays arrive more focused, ie more parallel, and call it a wash. ;)


I think the phenomenon is depth of focus becoming greater; however, as far as I remember theory, depth of focus is deeper the longer the lens, as a sort of inverse ratio to the depth of field. In other words, where you'd expect a wide lens to have greater depth of focus than a long lens, it only shows deeper depth of field than does a long lens, and has a shallower depth of focus. It's been so long since I used a view camera that I can't honestly remember which lens type was easier to focus, and that sort of camera shows those effects very clearly by its ease or otherwise of focussing different focal lengths.

If that theory is remembered correctly, then maybe the best test is done with your longest lens.

I did a quick check of a blank, marfil toned wall and I see no dust marks anymore. However, as with all things photographic, the real test is made in the field with real subjects!

Rob C

jim tillman

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Re: Is This Sensor Dirt?
« Reply #13 on: February 03, 2011, 01:46:41 pm »

This seems to have been touched on in some of the replies, but the issue can lie in 2 places:

1) On the sensor
2) Within the lens itself

It is not necessarily possible to determine where it lies by just looking at one image, but if it disappears from lens to lens then it is most likely the lens itself. When shooting at extremely small apertures, the shorter focal length lenses will reveal dust within the elements themselves. This is almost unnoticeable in lenses that are considered 'normal' in focal length or longer- it's usually found in the super wide lenses. This rears it's head with my view cameras and digital backs as well.
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Chipper1002

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Re: Is This Sensor Dirt?
« Reply #14 on: February 04, 2011, 08:10:16 am »

I have used the Arctic Butterfly, a brand new, clean, very fine, ladies' make-up brush, a bulb with nozzle that blasts a small amount of very focused air (be careful that you are not blowing something out of the bulb other than air! Give it a couple of squeezes against a mirror or a window first.) And when all else fails (about 4% of the time) I have used the Copperhill Method (http://www.copperhillimages.com/index.php?pr=Copper_Hill_Products) to do a wet clean. I was very nervous to try this the first time, but I quickly learned how easy and effective the wet clean process is. Others have recommended to NOT do anything about the dust, but I strongly recommend trying at least one or two of these methods. My local camera shop will do a sensor cleaning for $40, but you really CAN do it yourself quite easily.
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