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kearnage
24th of May 2005 (Tue), 02:48
Hi guys

As you can see this is my first post around here although I've been lurking around soaking up all your wisdom for a while.

My problem is as follows:

I got a 350D a couple of weeks ago and have been playing around with it. On one set of pictures (taken of the sun setting over the sea. I know it's been done a thousand times before but we all do it from time to time) I noticed there were dust particles on the sensor. I duly took my camera home and got the air blower out to fix it. What I would like to know is if any of you have a good way of testing for dust on the sensor? I assume they generally show up more on longer exposures but do you have a "best case" set of settings for picking up dust?

Secondly as an aside is there any way of uploading images back onto the CF card (while it's in the camera) from your pc? it will let me take them off but wont let me place them back again?? I don't have a card reader for now.

Thanks for any help you can give me. Maybe one day I will be in a position to help somebody else.

tim
24th of May 2005 (Tue), 03:16
Welcome to POTN :)

You should read this entire website, it's very helpful: http://www.pbase.com/copperhill/ccd_cleaning

kearnage
24th of May 2005 (Tue), 03:34
Hi Tim.


Cheers for that. There is some good info there. Alas my problem is not cleaning my sensor, I've already done that bit. I just wanted to know the best way of picking up if you still have any dust on the sensor.

I know shots of nice blue skies show them up well but here in bilghty the sky isn't always blue.
Thanks again though. I'll get reading.

robertwgross
24th of May 2005 (Tue), 03:56
If you don't have a bright blue sky, then a white interior wall will do. Just light it up as bright as you can with any kind of lights, and then shoot it with your camera with the highest f-number aperture where you can get a good exposure. Try f/16, f/22, etc.

Then, if you get gray-looking spots in your images, you still have dust on the sensor.

I've had enough practice, so I've gotten to the point where I can see dust spots with my naked eye. It requires that I have a very bright light directly overhead, with the camera chamber facing up. When held at just the right angle to reflect light, the spots can be seen. Otherwise, use the bright sky or the wall.

---Bob Gross---

tim
24th of May 2005 (Tue), 04:02
Hi Tim.

Cheers for that. There is some good info there. Alas my problem is not cleaning my sensor, I've already done that bit. I just wanted to know the best way of picking up if you still have any dust on the sensor.

I know shots of nice blue skies show them up well but here in bilghty the sky isn't always blue. Thanks again though. I'll get reading.

There's heaps of useful information there, not just on sensor cleaning. Like Bob says a white wall's fine too, so long as the wall's clean ;)

kearnage
24th of May 2005 (Tue), 04:08
Cheers guys.

Time to go find me a white surface.

erik-nl
24th of May 2005 (Tue), 15:03
no need to look far, just use your computer screen!
any painting program can give you a clean white screen.
take a shot with the smallest aperture your lens is capable of,
focus manually on infinity and gently move the camera during the shot,
making use of the relatively long exposure to blur the pixels of the screen itself.
applying 'auto levels' in Photoshop on this shot will most likely reveal more dirt on your sensor than you ever want to see.

kearnage
25th of May 2005 (Wed), 05:34
Thanks erik-nl although I almost wish you hadn't mention the auto levels in Photoshop.

Holy smokes does it show up more dust than you want to see. Luckily all the pictures I've taken since cleaning don't have any visible dust on them anymore. I'll be keeping the Photoshop levels trick in mind to scare anybody else who claims to have a dust free sensor haha

WaveRider57
25th of May 2005 (Wed), 07:55
Along this line, another question:

Would it help to change lenses and even clean my sensor, with it facing downward? It would seem more difficult for non-charged dust particles to settle on the sensor this way...or am I fantasizing in a world where gravity doesn't mean much?

What a great forum!

-Paul

JereMIA
25th of May 2005 (Wed), 19:51
Along this line, another question:

Would it help to change lenses and even clean my sensor, with it facing downward? It would seem more difficult for non-charged dust particles to settle on the sensor this way...or am I fantasizing in a world where gravity doesn't mean much?

What a great forum!

-Paul

That's funny, I always angle my camera body slightly down while changing lenses (with the same thought in mind)

I also was told by a professional, to wait five seconds after turning off the camera, before pulling the lens. Claimed the sensor remained charged and attracts dust for a couple seconds afterwards. (sounded like it could be possible)
I don't know if either of these techniques accomplish anything, but I practice them anyways. I figure its worth a shot to try and increase the duration in between cleanings!

tcaran
25th of May 2005 (Wed), 20:41
I was told the same thing - to face the body down when changing lenses - by a photography instructor I had who's been into it since the 60's. Before it was to limit dust on the mirror. Now it's the sensor.

WaveRider57
25th of May 2005 (Wed), 21:15
Excellent, and quite plausible advice, guy. Thanks!!

Pamela107
26th of May 2005 (Thu), 06:00
Ive Had my Rebel Xt for 6 days, yesterday I noticed in the upper right corner a black speck on photos taken with a Apert of 10 or higher. Im bummed , not sure if this is dust since I cant see any or if I should take the camera back. It shows up with both lenses on.

See sample photo.

Can I use canned air ? I used can air in the past on 35mm camera's , or will it hurt or dislodge something?
Im at work on a different computer, does the picture have half moon blue hue shapes to you or is it this old monitor?
Thankyou
Pamela

WaveRider57
26th of May 2005 (Thu), 08:28
NO!
the blast from the can is too strong, and could 'spit' some liquid, which would be a very, very bad thing. use an air bulb, and Canon says do not get the nozzle closer than the lens mount.

Pamela107
26th of May 2005 (Thu), 11:28
yes, Thankyou
I just read that in the manual , Im glad I checked.

Thankyou Waverider57

MgnDvD
26th of May 2005 (Thu), 16:26
I just posted my mad thoughts about the dust problem on a "Known gotchas with DRebelXT" topic

What I've noticed, that this dust problem, is a reall pain in the ...
With today's technology Canon's engineers haven't been able to come up with a solution !?
WHY do we have to spend additional resources(money,time...) on finding out how to clean the digital sensor ?
Instead of doing what we love to do, we have no other choice but to waste our time to discuss this issue!
I found today some dust while shooting. I still don't know where exactly this dust is, but it's still in the viewfinder. And I used the air blower on a lens
This issue occupies a very good part of discussion forums.
But if the dust is really on the sensor, then I'm already thinking...why do I need these headaches...why not to return the bloody camera and get the best Powershot ??

Did anybody have thoughts like that ?

Is Canon working on this problem ?

Why don't they issue "recalls" like in auto industry ?

The more wings this problem gets, the bigger market they will loose to Fuji, since Fuji has a solution to it.
Interesting to know...

Thanks!