Sensor or Lens Dirt?

[Paul Hadfield]

For quite some time i've had a few spots on my pictures that I dismissed as stubborn sensor dirt. I suspect that even the XTi sensor cleaning ability has it's limits. Not a problem, just grab a healing brush and it's as good as gone. The other night while messing around with settings, I decided to jack the F stop all the way up to see what happens and to my surprise, the stubborn spot came into detail along with a whole family of "spreckles". Before I even attempt to tinker, I am wondering now if this is not a sensor issue but rather the interior lens glass? Would be happy if it is, glass I can handle, sensors a different story.

Mods: stepped out of 500w rule for demonstration purpose

ISO 100, f11 (control)

ISO 100, f25 (note same area)

 

[Dennis Sherrod]

I am no great whiz on this other than what I have done.
One time it was a particular lenses. It was fine after I switched lenses it was gone. Had to get lense cleaned.
Second time, it was on the sensor. A lot of canned air and mirror lock up and it cured it.
I now keep a small can of air in my case so I can blow away dust before changing out lenses if I have been somewhere pretty dusty.
Others may have better ways or ideas, but this worked for me.

 

[Dan Robinson]

You can check for sensor dust by closing the aperture down all the way and shooting a picture of a light-colored wall or the clear blue sky. Try this with different zoom positions, and if the specks are in the same place, it's sensor dust (the most likely scenario).

 

[Jim Saueressig]

http://www.cleaningdigitalcameras.comhttp://www.cleaningdigitalcameras.com

How To Create A Test Image
To Check For Dust
To make a test image, you can use about any lens you want but an non-wide angle lens works better then a wide angle just because of the normal falloff found in most wide angle lenses. You want as much of an even exposure as possible from corner to center. The second consideration is minimum aperture opening; we suggest a lens that will stop down to f/22 or greater. We have found that a great subject to shoot for the test, is your monitor. Seeing that you already have to use a computer to view your test, there is no need to go elsewhere to make the test. You already have a willing and qualified subject right in front of you, why not use it. Prepare your monitor for shooting the test:

* Create a new image in Photoshop
* Fill it with white (most any solid color will do, but we prefer a lighter one)
* Zoom in until it fills your screen

Set the camera to the following:

* Mode - Aperture Priority
* Setting - Aperture to minimum f/22-f/45
* Lens - Manual Focus set to closest focus setting (if shooting the blue sky, then infinity)
* Features - Turn "OFF" all special function like "sharpening"
* Take Picture - shoot camera facing your monitor. Depending how bright your monitor is, your exposure may be a couple seconds. During this exposure, move your camera back and fourth being careful to not to point the lens outside of your white box. Moving the camera during the exposure insures that you are not taking a picture of dirt on your monitor. This should be done within a matter of an inch or two from your monitor.
* Photoshop - Take the image into Photoshop and do a ++ for "auto level" You can lighten or darken if needed.
* Inspect Image - You can now see where you do or do not have dust. Remember that what you are looking at is an image that is flipped 180° (top to bottom) from when you're looking straight in on your sensor. What shows on the bottom of the image will be towards the top of the camera and visa versa...

Before Converting in Photoshop

Converting in Photoshop

After Photoshop and Before Cleaning

After Cleaning

 

[Dick McGowan]

I might have a little dust problem on my old XT...yours is nothing compared to this Paul! LOL, at f/7.1 it starts to show.....this is at f/22

 

[John Wetter]

Most likely sensor dirt if you've thoroughly cleaned the lens. Pop on another one and see if the dirt is still there. I always send my camera in at the end of the season for a professional cleaning. Even though I rarely switch lenses in the field, it's just so dirty that I think it's a good idea.

 

[Greg Campbell]

It's almost certainly dust bunnies on the CCD filter. Try canned air, that ought to get most of the junk.

 

[Brandon Ivey]

Does canned air really work? It won't leave any residue on the filter? I have always heard that the sensor needed to be cleaned with a sensor cleaning kit. Canned air would save time and money! Would this have any long term effects on your camera or sensor?

 

[Dennis Sherrod]

I have used it for about three years with no problems. Just don't tilt the canned air. Keep it upright when spraying.

 

[Jim Saueressig]

DON'T USE CANNED AIR!

Sometimes your lucky but here is what can go wrong:

They are never 100% pure and can spew more crap on your sensor.

Many have oils and other contaminants that can mess your sensor up badly. Some have chemicals that can destroy the filters covering the sensor. Most have high moisture that can possibly destroy your camera.

Use an air blower.

If you need to wet clean it use the directions on the site I listed above. It sounds far scarier to do than it actually is.

 

[Dennis Sherrod]

DON'T USE CANNED AIR!

Why is that Jim? Is it suppose to hurt something?

 

[Paul Hadfield]

Yep, sensor dirt is what it was. Reviewing the link you posted Jim, I did not know that sensor cleaning was such an easy task. You never actually touch the sensor (on a Rebel anyways) but rather, clean a high pass protective filter. They have pdf to the Canon Rebel instructions for which on page 39, explains how to set the camera into cleaning mode. Reading the instructions... there's a novel idea... lol! Anyways, spending a fair amount of time last night using tight weave swabs that came with a cleaning kit from when I bought the camera, I got most of the dirt minus a few stubborn specks. Either way, thanks to all of you for posting this information.

before

after (much better though I think these particles are attached by static because they seemed to get pushed around without detaching)

 

[Jim Saueressig]

Why is that Jim? Is it suppose to hurt something?

Yeah, I re-edited that post. I posted that and went looking for an article on how bad that was to do, I cannot find it yet but posted the reasons there. Its the one time the air goes bad that will destroy your camera.

 

[Jim Saueressig]

Yep, sensor dirt is what it was. Reviewing the link you posted Jim, I did not know that sensor cleaning was such an easy task. You never actually touch the sensor (on a Rebel anyways) but rather, clean a high pass protective filter. They have pdf to the Canon Rebel instructions for which on page 39, explains how to set the camera into cleaning mode. Reading the instructions... there's a novel idea... lol! Anyways, spending a fair amount of time last night using tight weave swabs that came with a cleaning kit from when I bought the camera, I got most of the dirt minus a few stubborn specks. Either way, thanks to all of you for posting this information.

I bought the Eclipse E2, and a pack of pec pads and use it when I cannot remove it with air. Often particles of pollen are sticky enough that air will not work and so you need to use the wet method.

 

[Dennis Sherrod]

Yeah, I re-edited that post. I posted that and went looking for an article on how bad that was to do, I cannot find it yet but posted the reasons there. Its the one time the air goes bad that will destroy your camera.

Thanks Jim. Yeah, I have found in the past, thankfully not on a camera, not to tilt the can because of moisture. I have also heard of "off-brand" canned air of particle problems, but have heard or read somewhere that the so-called name brand is better.
I think it is probably better that people clean the inside the way you are speaking of compared to what I said. One bad can and I guess it could really mess up.
Yet, I think I would still use it on the outside of the body of the camera and before changing lens.