DSLR Sensor Dust/Cleaning

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Bob Buchanan

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? ? Have just had a bad bout with sensor dust on my Rebel XT DSLR--and thought I would pass along info on the experience (or rather, "bad" experience :(). I had read an article on this some time ago, but had since forgotten about it. I have been shooting w/my XT for several months now, and did not notice the problem until several weeks ago. Unfortunately, the job I was doing was construction progress -- so the shots in question cannot be done over. Thank goodness for digital darkroom. Also, the shots I was doing were at small aperture settings (F20.0 to F40), so the wider DOF make the dust spots stand out more.

Most of my work prior to that has foliage or other mixed background. However, when looking closely at a clear blue sky above a horizon, I noticed numerous fuzzy little thingy's that reminded me of a chemistry class years ago. At first I thought I had dust on my lens -- but tests showed that it was dust on the CMOS sensor (CCD sensors have the same problem). The booklet w/the camera (as all DSLR's probably do) had a process to clean it. I decided to first take the camera back to the Pro shop of my purchase to learn more about the problem. Was glad I did. Here's some of what I discovered:

o The dust is not on the sensor, but rather on the glass cover over the sensor. The sensor itself is further protected by the shutter and the mirror in its normal down position.

o The dust entry happens during lens changing. Actually, the dust doesn't go right to the sensor, but rather builds up on and around the SLR mirror. The sensor builds an electric charge over time. So when a pic is shot, the mirror goes up, the shutter opens, and the sensor's charge sucks the dust in. Some pros tell me that the pumping of a long lens creates a vacuum that will then suck dust into the housing when that lens is removed.

o The technician at my camera store cleaned the sensor for me. He suggested a hand bulb type blower and suggested "never" using a gas powered blower. He first removed the lens and blew dust from the mirror and housing around the mirror. Was amazed at how much was in there. He then raised the mirror and cleaned behind it. He then put the camera into sensor cleaning mode and cleaned the sensor itself. He then took a test shot and put the results into a computer graphics package -- and the dust appeared to be gone. Unfortunately it wasn't with my follow up tests so I returned to the shop.

o This time the authorized service person cleaned the sensor. He said that there was still tons of dust even after the initial cleaning. His cleaning was more thorough -- and now my test show no dust.

Anyway, I am now very conscious of this problem and am very careful when changing lens. They suggested I always hold the camera in a down position and keep my lenses covered when not in use. They also suggested a general bulb cleaning of the mirror and housing after a day of shooting if the lenses are changed -- or at least after several sessions. They did not charge me for the pro cleaning, but mentioned if my camera was not so new, the normal charge for a sensor cleaning is $75.00. Ouch!!

Here's a couple of articles I found that are pretty detailed and cover most of the points I mention here.

http://thomashawk.com/2006/04/10-tips-for-new-digital-slr.html

http://www.photosafaris.com/Articles/CleaningTheSensor.asp

Those with fixed lens cameras do not have this problem as the sensor is always protected from dust.?
 

BernieD

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Goodyear, AZ
Bob

I guess you are just to have to upgrade to the next model above the Rebel. Recently read a review where the new model's primary improvements were anti-dust devices; electrostatic "magnets", a shaker to drop all the lens dust away from the lens and a new lens cap which is less prone to create dust. I can't remember anything further about model, price, etc. except for the comment that after they introduce new features on that camera it eventually filters down to the Rebel.
 

Bob Buchanan

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BernieD said:
Bob

I guess you are just to have to upgrade to the next model above the Rebel. Recently read a review where the new model's primary improvements were anti-dust devices; electrostatic "magnets", a shaker to drop all the lens dust away from the lens and a new lens cap which is less prone to create dust. I can't remember anything further about model, price, etc. except for the comment that after they introduce new features on that camera it eventually filters down to the Rebel.

Thanks, Bernie. It may be the other way around in that they put auto cleaning in the Rebel first. The latest model is the Rebel XTi that came out last month. In the Canon article HERE I found that info.

Unfortunately, I am one model behind -- but that's OK. Now that I know what to look for and how to lessen the dust happening, I think I'll stay with what I have. My next move upward in a Canon body will probably be the D30 upgrade (D40 or D50). It will be interesting to see the reviews of the XTi and how well the auto cleaning works. It looks like a feature I would certainly want on my eval list.
 

Pierat

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The new sensor-cleaning Canon camera is a digital Rebel at maybe $800 street. http://web.canon.jp/Imaging/eosdigital3/

Sensor cleaning with a blower can be dicey. From an optics career expert/photographer, a tutorial: http://www.bobatkins.com/photography/tutorials/sensorclean.html

Good light and good shooting!
 

Mike (ex-f-221)

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Bremerhaven, Germany
Had this dust-problem with my Canon EOS 10D. Solved it using dry cotton swabs (sometimes called Q-Tips). Removed the lens, cleaned the mirror with the Q-Tips, raised the mirror and cleaned the sensor with the Q-Tips - done. When I see dust-spots again after a while I repeat the procedure. Some people use alcohol to clean the sensor (wiping, not drinking). Heard of a cleaning-method where rubber-pens shall pick up the dust. But heard that this is not the best way.
 

Karl

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Bob,
If the brush method fails, the best thing I've found are those small foam makeup applicators that women (mostly  ::)) use. Use one dry, and follow with one slightly dampened with isopropyl alcohol only if the dry one doesn't do a complete job. 
 

Pierat

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I've read that the mirror coating can be damaged easily. The writer recommended not touching it. Don't know how true it is. Seems to me that optical glass could get scratched by rubbing especially if something like grit is under the swab. The link I posted earlier to Bob Atkins' site contains a lot of info on the subject. My 10D's sensor doesn't seem to gather that much dust (that I notice). However, the dust on the sensor shows up more at smaller apertures, and I haven't done a lot of that work recently. I don't have expensive lenses so I try to keep them in the "sweet spot" around f/8 when the situation permits, for image quality reasons.
 

Bob Buchanan

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Karl said:
Bob,
If the brush method fails, the best thing I've found are those small foam makeup applicators that women (mostly? ::)) use. Use one dry, and follow with one slightly dampened with isopropyl alcohol only if the dry one doesn't do a complete job.?

Hi Karl -- I didn't realize you are shooting w/a DSLR. Have you gotten a new setup since QZ 2 years ago? If so, tell me the details . . .
 

Bob Buchanan

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Pierat said:
I've read that the mirror coating can be damaged easily. The writer recommended not touching it. Don't know how true it is. Seems to me that optical glass could get scratched by rubbing especially if something like grit is under the swab. The link I posted earlier to Bob Atkins' site contains a lot of info on the subject. My 10D's sensor doesn't seem to gather that much dust (that I notice). However, the dust on the sensor shows up more at smaller apertures, and I haven't done a lot of that work recently. I don't have expensive lenses so I try to keep them in the "sweet spot" around f/8 when the situation permits, for image quality reasons.

Well, after my bought with this thing, I've decided to be very careful when changing lenses, keep the camera pointed downward when making the changes, and to keep the housing clean with a hand bulb blower after any session that I make multiple changes. For the time being, I am not going to void the warranty by attempting to clean the sensor cover at all myself. With me, it will be hand blowing from the shutter outward. If a spot shows then, I will attempt the sensor w/the blower -- and if it doesn't work, will make a decision as to what to do next when it happens.

If they do show up again I will probably find them right away -- as I try shoot most all scenery stuff from F20 to F40 if I have enough light. My people stuff usually has very shallow DOF and environmental backgrounds so that shouldn't be a problem.

The two articles I posted plus yours should tell the story and allow others to make their own decisions. Thanks for your comments, Pierat. What kind of work do you enjoy the most in your photo business?
 

Chet18013

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Full time in RV. Home is where we are parked
Here's a link to the "sensor cleaning bible".

http://www.pbase.com/copperhill/ccd_cleaning

I've been using this process since 2003 with excellent results.

Here's the cleaning kt I now use.

http://www.giottos.com/eng_public/products_variation_detail.asp?ProductID=79&VariationID=363

Like Bob says, ALWAYS hold the camera body with the lens pointing down when removing and installing a differrent lens.  Dust settles down, and will be less prone to enter the body this way.

One of the biggest sources is WEAR of the metal of the camera and lens attachment rings. They are usually a softer metal like brass/bronze. If you remove a lens and look in your camera body, you can easily see small metal particles/dust around the edges inside. Very carefully use of a "Q-Tip" will easily remove these particles before they move around and eventually get to the sensor. I first use the Q-Tip, then the blower and if the is dust on the sensor, then clean it as the last step. Remember the Q-Tip is positive removal, the blower just moves things around. Never, never use a Q-Tip with the mirror up and the sensor exposed.

Chet18013
 
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