Lens dirt -- suggestions?

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Lens dirt -- suggestions?

Postposted on Sat May 25, 2013 9:19 pm

So I've noticed some splotches here and there on some of the shots I've taken and today was the worst. Grey and overcast with bright diffuse light, shooting up at the sky. I have a sequence of shots that clearly demonstrates the dirt, and also proves it to be inside the lens.

First, at F10. You can see a couple of blobs, one 45 deg down from the tail and one 30 deg up.

Image

Now, at F18. Same blobs, only a bit more resolved now. One straight down from the tail, one at 30 deg up and left.

Image

Now, finally, at F32. Well defined dust specks.

Image

So, they are in the lens, somewhere in front of the aperature, but not on the front element or protective filter. Unfortunately, a lot of the shooting I do is with the sky as a background for most of the shot and they are pretty noticable all the way down to the F6-F8 range with the sky as a background. Any suggestions? Obviously I can send it to Nikon to be cleaned, but I'm curious if anyone has other suggestions.

--SS
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Re: Lens dirt -- suggestions?

Postposted on Sat May 25, 2013 11:41 pm

Looks more like sensor dust, not lens dirt - if it were on the lens, you'd get a small loss in clarity and contrast, but not obvious spots in the pictures. Spots like that have to be on one of the two focal planes - either the subject, or the place where the image forms.

If you're not convinced, grab another lens and try again. You'll find that you'll get spots in the same spot - they'll be much more defined at small apertures (f/16 or f/22, f/32 if you have a lens that can do it.)
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Re: Lens dirt -- suggestions?

Postposted on Sun May 26, 2013 5:51 am

+1 for the sensor dust. It is most prominent at long focal lengths and small apertures, so try a zoom lens at full telephoto and closed all the way down to confirm. As for cleaning, there are many dslr cleaning kits out there. First I would try one of the many blower kits available. Most of the dust can be dislodged this way. If something unsightly remains after that, give the camera to a professional (send it to Nikon in your case), or if you feel very confident, clean it yourself with one of the specialised kits with swabs for the sensor. Do not improvise and be very careful as sensor damage is a real possibility if you wipe it yourself, especially if you haven't done it before. :wink:
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Re: Lens dirt -- suggestions?

Postposted on Sun May 26, 2013 8:43 am

This looks exactly like the sensor dust I had on a brand new camera. It was only visible in sky shots. I priced a local shop that would charge $50 for a cleaning. You can also buy the cleaning products online and do it yourself. Also, the post above mentions a blower kit - that sounds like a good idea.
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Re: Lens dirt -- suggestions?

Postposted on Sun May 26, 2013 9:38 am

flip-mode wrote:This looks exactly like the sensor dust I had on a brand new camera. It was only visible in sky shots. I priced a local shop that would charge $50 for a cleaning. You can also buy the cleaning products online and do it yourself. Also, the post above mentions a blower kit - that sounds like a good idea.

I'm surprised that more camera makers haven't adopted the "ultrasonic wiggle" that Olympus has on their 4/3 bodies. About the only good thing about my Oly.
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Re: Lens dirt -- suggestions?

Postposted on Sun May 26, 2013 12:04 pm

Yeah, sensor crud. I had to sit down and think back to my optics sections in physics to wrap my head around why it is so clear at long focal length+small aperature. It's actually a very good example of what a lens does to the rays of light...

Nikon does have a "sensor clean" function on this body, but it hasn't helped in this case. I've managed to get rid of two of them with puffed air -- the two on the left side of the frame. The two on the top towards the right are being more stubborn. Doesn't help that they are so small as to be pretty well invisible, even to my good eyes.

--SS
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Re: Lens dirt -- suggestions?

Postposted on Sun May 26, 2013 1:38 pm

Well, I can't see the two remaining spots on the sensor and I don't have any APS-C swabs right now so I'll just have to let it be. The spots are about 0.07mm diameter, based on the size they show up on the image. They only become noticable above F-12 @200mm and aren't too bad until F-20 or so. That is taking a picture of a white screen with focus set at infinity.

--SS
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Re: Lens dirt -- suggestions?

Postposted on Sun May 26, 2013 2:20 pm

Captain Ned wrote:
flip-mode wrote:This looks exactly like the sensor dust I had on a brand new camera. It was only visible in sky shots. I priced a local shop that would charge $50 for a cleaning. You can also buy the cleaning products online and do it yourself. Also, the post above mentions a blower kit - that sounds like a good idea.

I'm surprised that more camera makers haven't adopted the "ultrasonic wiggle" that Olympus has on their 4/3 bodies. About the only good thing about my Oly.


All of my Canon's do a 'sensor cleaning' sensor shake when turned off; I assume that's similar to an ultrasonic wiggle?
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Re: Lens dirt -- suggestions?

Postposted on Sun May 26, 2013 2:58 pm

Airmantharp wrote:All of my Canon's do a 'sensor cleaning' sensor shake when turned off; I assume that's similar to an ultrasonic wiggle?

Yeah, the Oly does it when you turn it on. When I bought the camera they were the only maker with the feature.
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Re: Lens dirt -- suggestions?

Postposted on Tue May 28, 2013 12:17 pm

I actually cleaned sensor dust out of my 40D on two occasions using an optical fluid and special foam q-tip, then polished with a cloth designed for eye glasses. Very, very fidgety but it can be done.
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