Posted by Mel Ladewig on March 8, 2006 at 12:29 PM
I've noticed a problem creaping up in my picutres with one of my lenses. At first I thought it might be dust on the sensor, but it is only showing up when the aperature is stopped down to f16 or smaller and only with one lens. They are repeatedly appearing in the same position. The lens is clean on the front and rear element.
The problem is out of focus dark spots in the image. They are approximately 30-35 pixels across.
Does anyone have an idea about what might be causing this?
Looks like sensor dust to me. My remedy is quick - I use the visible dust set up.
1. With mirror locked up - blow like crazy with the hurricane blower.
2. After "charging" the sensor brush with an air duster, drag the brush across the sensor. Do this twice.
Also, Visible Dust has short videos on their site.
Well, if your lens elements are truely clean and it shows up ONLY with this lens, I'd have to conclude that dust somehow has entered the lens and is on an interior surface that would require a technician to clean.
The variation with aperature is normal. It's amazing how "clean" my sensor looks at f1.4
I would concur with BIll, on one of my Nikon 18-70 lenses (also known as the "Kit" lens) somehow I have a spec of dust inside the front element, I have not inspected the images close enough to determine if it is causing any issues.
Sensor dust is affected by aperture, apparently; something to do with the fact that the dust isn't directly on the sensor, but on a glass filter above the sensor, combined with light angles... What lens is affected, and which aren't? Is this a mid-range lens, or at one of the ends?
This is a Tokina 28-70 f2.8. Like I said, the problems are only with this lens. I've used both a 17-40L and 70-300 IS at small aperatures with no issues. I'll be looking into how to get this tokina serviced when I get a chance. Not going to happen for a while though. I've only had the lens 2 months and not anyplace dusty. Not sure how this happened.
Discussion
7 repliesThe problem is out of focus dark spots in the image. They are approximately 30-35 pixels across.
Does anyone have an idea about what might be causing this?
Looks like sensor dust to me. My remedy is quick - I use the visible dust set up.
1. With mirror locked up - blow like crazy with the hurricane blower.
2. After "charging" the sensor brush with an air duster, drag the brush across the sensor. Do this twice.
Also, Visible Dust has short videos on their site.
Good luck,
Dave Showalter
Problem is that it is not there when shooting at wide aperatures or with any other lens.
M-
The variation with aperature is normal. It's amazing how "clean" my sensor looks at f1.4
I would concur with BIll, on one of my Nikon 18-70 lenses (also known as the "Kit" lens) somehow I have a spec of dust inside the front element, I have not inspected the images close enough to determine if it is causing any issues.