Issues with DA* 16-50

I discovered something rather unstartling when I came back home to review my photos (it was too bright outside, so I couldn't spot it on the screen).

This is a cutout from the 1.1 square (3x3 grid) of my image.



What is it?

My thought is that it is something that have gotten inside the lens.
Because after I spoted it, I checked the mirror, the sensor, and cleaned the front and back elements of the lens. Took a test-image, and same issue.
I also tried with another lens, and nothing there.


Also, do anyone have any 'test-images' of what kind of sharpness I should be able to reach with a good copy of the lens wide open?
I have never really come across comparisons of different copies of the same lens before, only a single copy compared to a completely different lens.

This test can be done by stepping 3 meters away from a piece of paper with a bunch of different sized letters on it. And take images at 16mm, 20, 28, 35, and 50mm.

Must be something on the sensor. I had similar problems a couple of months back and nothing showed up on any of the in-camera tests or by looking at the sensor itself, just on the photos.

The cleaning kits aren't cheap, but do a very good job. The only other possibility is oil or something on the inside of the lens, but imagine that would show up when looking at it.

Best bet is try the same image with 2 lenses. If it's still there it's the sensor.

A hair on the sensor would be my guess.

Actually the OP said he had tried it with another lens (which I missed when first reading it) and it was o.k. so guess it couldn't be the sensor in that case?

O.k. Didn't know that, thanks.

Found it.

No idea how it got there, and it was so tiny there is no wonder I missed it on the first inspection of the sensor.

My test was also not done with a small enough aperture (thanks for that Mike, I had no idea). It explains why I had not noticed it earlier aswell. I seldom shoot smaller than f5.6.

I did however also notice 4 small dots on the sensor, dust specs or not, I dunno. They are a bit a part, and 'glued' on, because a little bit of wind wasn't able to get them moving.


The comparisons of different copies of the 16-50 is still something I am curious about. I have yet to test this copy thoroughly, but sometimes I feel it is a bit soft. However I have no idea if it is abnormally so, or not.
(The lens is still within the warranty period, so if I find something I can get it exhanged.)

They are probably pollen grains, which are sticky.
An Arctic Butterfly might remove them, but the pollen may also stick to the brush. Best to use a wet solution, PecPads and Eclipse fluid should shift them but it can take a bit of practice getting the sensor smear free.