Dust or not

[Curtis Cunningham]

I'm not sure exactly why my camera does this, but if you'll look at the images below, could you tell me why you see what appears to be dust on the left, while none seems to exist on the right. These images are straight out of the camera with no processing applied yet. Originally, I thought it was dust on the sensor, so I cleaned it as best I could, but the 'dust' issues still remained. Then I thought it was something on my backdrop that was causing the problems, but with the change in aperture, the problems seemed to go away.

I'm still figuring out the best lighting, but I don't think lighting is the issue. I'm sure there's a technical explanation for it, but that has always been a weakness of mine (understanding the technical side of things).

[Ken_Bennett]

The dust is there in both shots. The difference is the aperture. A wider aperture (f/4) shows dust spots as large, blurry blobs. A very small aperture (f/29) shows dust spots as very small, in-focus black dots. (Or hairs or whatever they really are.)

The best way to check for dust is to stop down to f/22 or so and shoot a blank wall. This will show every dust spot.

--Ken

[Dennis_Vied]

When I clean my sensors, it's seldom that I get it on one try. You need to check it after each try. I shoot the sky, which gives me a small aperture, (to show up the dust spots), and an evenly lighted subject with an uncluttered field. (Just be careful not to shoot the sun). I'm shootin' and cleanin' tell it comes up clean.

[Noel_Carboni]

Regarding understanding why dust shows up more sharply with a small aperture than with a wide one.

Imagine you're standing on a white sidewalk.

When a big white cloud is covering the sun your shadow on the walk is soft.

When the sun is out - i.e., the light is coming mostly from one direction, your shadow on the walk is small and hard.

-Noel

[MikeOJohnson]

Suggest you try the Sensor Loupe by VisibleDust. It eliminates the steps of taking a photo, downloading and viewing on the computer. In my experience it saves a lot of time.
Mike

[DigiCamPix]

Dust it is... happens to all of us shooting DSLR's... good advice above.