Lens Smudge ?

<p>I have a smudge on my Nikon 24-70mm F2.8 lens. It is not the sensor, it only appears with this lens. All my other lenses are clear. Upon checking this lens, I do see some dust on the screw in side. To me this doesn't look like a dust spot and normally dust in the lens doesn't affect the image. Just wondering if this could be the dust spot showing up like a smug. Only appears at 22mm, but I shoot landscapes at this range most of the time. Suggestions and thanks ... Ray.</p>

<p>Sorry, here is the jpg of the smudge.</p><div></div>

<p>I see a few dust spots...try a hurricane blower to get the dust off the lens. </p>

<p>It still looks more like sensor than lens, although the latter is not impossible. Often, a speck on the sensor cover will only show up at certain f/stops and so on. I have a series of pictures taken one morning with, as it turned out, an incredibly dirty sensor. However, although the dirt was clearly on the sensor the whole time, only some of the shots actually show the "smudges" in the image. Looking at the metadata just now, I see that the dirt showed up most clearly with my 24-105mm, but hardly at all with either a 50mm or a 15-30mm lens that I also used that morning (these, of course, are not Nikon lenses, but the principle is the same).</p>

Is it possible to only show on one lens if all were shot at the same settings?

<p>I clearly see a dark area that looks like something on a filter or lens. I'm guessing it only shows up at a wide angle because the longer lengths put it more out of focus because of the reduced depth of field.</p>

<p>I'd get it checked out. Can you take a shot of a gray wall or something? It'll probably show up more there. How new is the lens. Certainly under warranty, but you're going to have to do some work to "prove" that there's a problem to Nikon, perhaps.</p>

<p>EXIF data shows that sample photo was taken at f/22, which is perfect for revealing dust on the sensor. That's almost certainly what the smudge is.</p>

<p>However, there's also an odd, very distinctly defined dark spot at the upper right corner. Not normal light falloff that you'd expect to see with a wide angle lens wide open, but a very distinct shape. Was there something in the frame that might have caused that? A tree limb, roof edge, etc.?</p>

<p>Wow, Lex. You really think that's dust? dust on the sensor has never been that "subtle" for me. In fact, my most recent run-in with sensor dust was really ugly!</p>

<p>In my first post I meant F22, not 22mm. The lens is about 1 year old. Just showed up recently. I also took some shots with my 17-35mm, same F stop (22) and same MM (35) ... no smudge. Also used my 50mm, and 70-200mm at F22 ... no smudge. Of course I couldn't use the same MM on these lenses. Tomorrow, I'll stop by The Photo Center and try using another 24-70mm lens.</p><div></div>

<p>Is it just me or does the smudge seem to migrate between shots a bit to the left when comparing those two shots? Also, when goofing around with curves in PS, there seems to be another "smudge" directly below the clearly visible smudge. And that second "not so visible smudge" seems to migrate even more. So that might rule out sensor and confirm that the problem is probably with the lens?</p>

<p>Hi Janne. The two shots were shot at different MM. One at 35 the second at 50. That would probably explain the slight location change. Thanks for all the responses. I'll let you know what happens at the local camera store when I try a different 24-70mm lens.</p>

<p>If you de-saturate in P'shop and then Auto levels, you can definately see small black specks that are dust particles on the sensor's surface (well AA fliter). There is also a distinct secondary 'blotch' bottom left aswell as the more obvious top left one. <br>

Lump of something on the inside of the rear element is my guess. At f22, it is appears in the 'depth of field' or is that 'depth of focus'?</p><div></div>

<p>Thanks, Mike. The smudges were definitely in the lens. I went to my local camera shop and tried a new 24-70mm. At the same settings there were no smudges. Came home and gave the rear element a good cleaning with a rocket blower. Must have dislodged it ... no more smudge spots. Also used the rocket blower on the sensor. Got rid of 95% of the dust spots on the sensor. I can live with a the couple of remaining ones. Just glad, I didn't have to send the lens for cleaning. Can't bear to be without this lens for any length of time. It's my workhorse. Thanks to all ... Ray.</p>