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Old Aug 28, 2005, 9:24 AM   #1
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Hi everyone,

I've had my rebel XT for about a week now and I just noticed something really strange. I went to the zoo yesterday and when the sky was in the picture, there was a large smudge in the top left. I have never touched my lens so I don't know what caused it - but anyway when we got home luckily my friends dad had some lens cleaner and we went through and cleaned it. However, there's still a dot there and I'm worried something is wrong with the lens? What else could cause a small dot/smudge to show up in all my pictures?
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Old Aug 28, 2005, 9:53 AM   #2
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Here are sample pictures to show!

Note: I was taking pictures of an animal in burst mode? and the smudges appeared in one picture and the pictures were only split seconds apart at the same angle. The images are cropped to the top left section. The first image is from yesterday, the next two are from today after it has already been cleaned.








The dot in the last two pictures is in the same place as the dot from yesterday (but the big smudge is gone)
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Old Aug 28, 2005, 9:58 AM   #3
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You have a tiny spec of dust on your sensor. This is totally normal, and there is nothing wrong with your camera ... and you don't have to return it and get a new one. Some cameras come already with a bit of dust on the sensor ... and sometimes you put it there the first time you mounted a lens on the body.

You should go to your local camera shop and pick up a medium or large Giottos Rocket blower then follow the instructions in your camera manual for sensor cleaning. Whatever you do:

1. DO NOT blow into the camera with your mouth. One very tiny drop of saliva will look like a monster blob on your images. Remember that that ugly blob you are seeing right now is from a spec of dust you probably won't be able to see.

2. DO NOT use propellants to clean the mirror or sensor. There is too big a risk of imbedding something in the sensor from a potential high velocity blast. Sometimes canned propellants (sometimes called canned air ... even though it is never air) will spit a bit of liquid that will be very cold as it evaporates and can potentially damage something.

3. DO NOT wipe the sensor with anything that isn't made for sensor cleaning, and if you don't like to follow instructions, send your camera in to Canon for cleaning if the Rocket blower can't remove the spec. Also note that Canon does not recommend using anything except a blower, so any other method you use is at your own risk (the most popular method is the "Copperhill method").

Personally I don't worry about the dust too much since it only appears at a high f-stop and is only noticed in the sky. You can easily clone the specs out in photoshop. I bought a blower when too many were showing up, and now I only have one spec that I notice when I shoot on a bright sunny day (high f-stop).



Here are some tips for you:

* Don't leave your camera laying around, or even in your camera bag with the body cap off. Dust will enter the camera quite quickly.

* Change lenses with the lens mount on the camera body pointed downwards to help minimize the amount of dust that gets on your sensor from changing lenses.

* Don't change lenses ina dusty environment. If it is even a bit dusty, change lenses inside a clean plastic bag.

* Some feel that you should turn your camera off so the sensor doesn't have a static charge to attact dust when you change lenses. I have no idea if this really matters, but it's probably a good habit anyway.



I hope this helps!



Bob

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Old Aug 28, 2005, 10:10 AM   #4
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Forgot to add that even if you are very careful you are going to get lots of little dust specs on your sensor. So, with a DSLR you have to think of sensor cleaning as just another routine you have to do ... no different than needing to clean a lens on occassion.

Every once in awhile take a picture of a clear blue sky at f22. Clean the sensor then repeat taking the image and the number of spots will decrease. If you have a stubborn spec that a blower can't remove then you can either ignore it (clone it out in PS if it shows up in the image), send the camera to Canon to have it cleaned, or clean it yourself with something like the Copperhill method.
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Old Aug 28, 2005, 10:18 AM   #5
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Thanks a lot for the response! I was quite worried because the other specs were cleaned no problem but that one stayed so I had no idea what's wrong.

I called bestbuy (where I purchased the camera) and they're very friendly and I think they'll take a look at it for me and try to clean it!

Thanks again for the response, you've saved me a ton of worrying!


And thanks for the advice on precautions!

I always keep the lens cap on whenever I'm walking around or putting it in my bag or anything.. i treat this thing like my baby haha. i know I have to keep it up forever too if I want to be able to use this in the future.
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Old Aug 28, 2005, 10:47 AM   #6
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Hi Doug,

I wouldn't let anyone from Best Buy touch my camera. Instead, go to a specialty camera shop that deals with pros.

If you don't have a quality camera shop in your area then I would either do research on-line and learn how to clean it yourself, or send it in to Canon.
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Old Aug 28, 2005, 11:23 AM   #7
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I have a 20D and appear to have a very similar problem. The two sunflower pictures here http://agrajag.visualblogging.com/ar...02792988/83907 show a blemish at the top left of the image.

Can you confirm that this also looks like dust?

Thanks for any help. If it is, off to get a blower tomorrow.

Gareth
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Old Aug 28, 2005, 2:44 PM   #8
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Agrajag wrote:
Quote:
I have a 20D and appear to have a very similar problem. The two sunflower pictures here http://agrajag.visualblogging.com/ar...02792988/83907 show a blemish at the top left of the image.

Can you confirm that this also looks like dust?

Thanks for any help. If it is, off to get a blower tomorrow.

Gareth
Yup, that is a spec of dust on your sensor. It would be pretty easy to remove using the clone tool in Photoshop. If you shot the image with a higher f-stop it would have been even more noticeable.
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Old Aug 28, 2005, 8:14 PM   #9
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Just wanted to say thanks again.

I went to blacks today and bought a cleaning kit for $7CDN which had a blower/brush end, lens cleaner, lens cloths, and some fine qtips. I used the blower on my sensor and now my pictures are perfect! Bestbuy was willing to replace my camera once they had new ones in stock too so it's great to see they stand behind their sales.

Oh, and I was just wondering what an Fstop is? I noticed lenses have a rating like f/4 or f/1.8 and I've seen it on my camera, but I'm not entirely sure what it is.



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Old Aug 28, 2005, 11:39 PM   #10
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Hi Doug,

This should help you understand f-stop:

http://www.uscoles.com/fstop.htm

There are also a few websites with info about basic photography that would help you out. One that is a good place to start is hosted by Kodak:

http://www.kodak.com/eknec/PageQueri...q-locale=en_US


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