Canon Digital Photography Forums  

Go Back   Canon Digital Photography Forums > 'Equipment Talk' section > Canon EOS Digital Cameras
Register Rules FAQ Members List Search Today's Posts Mark Forums Read



Reply
 
Thread Tools Display Modes
Old 4th of April 2005 (Mon)   #1
nater
Member
 
nater's Avatar
 
Join Date: Mar 2005
Location: Chicagoland
Posts: 201
Default Hot pixels? Please help me diagnose a problem with my Rebel XT

Hello everybody. I've been playing around with my new Rebel XT from Dell, and I decided to try testing for hot/dead pixels. I took 1- and 30-second exposures with the lens cap on, and found one dead pixel (white) and one or a couple hot pixels (blue). Then I took some pics of my white walls, and found much more interesting results. In the resized example pic below, you can identify 40+ dark spots.

Are these hot/dead pixels? If so, why did only a couple show up in the lens-capped pictures?

I know what the problem is not. It is not my lens (problem happens with both of my lenses), or my walls (identical pattern of spots appears when photographing various white walls and ceiling).

Does anyone have thoughts? It seems like a significant problem to me, so I'm planning to call Dell tomorrow and ask for a replacement. Is there something I'm missing? Thanks for any help...

- Nate

(edit: the quality of my uploaded pic is quite diminished, but you can still see the strange dark spots I'm referring to)
Attached Images
File Type: jpg IMG_4784 (Medium).JPG (9.9 KB, 252 views)
__________________
Canon 70D || Canon 10-22 f/3.5-4.5 || Canon 17-55 f/2.8 IS || Canon 24-105 f/4L || Canon 70-200 f/2.8L IS || Sigma 30 f/1.4 || Canon 50 f/1.4 || Canon 85 f/1.8 || Canon 60 f/2.8 Macro || Rokinon 8 f/3.5 fisheye
Feisol CT-3401N Tripod || Kirk BH-3 Ballhead
Buy & Sell Feedback: POTN || FredMiranda || ebay ~~~ Pro tip: Separate focus from shutter
nater is offline   Reply With Quote
This ad block will go away when you log in as member
Old 4th of April 2005 (Mon)   #2
Dante King
"Cream of Corn" BurgerMeister
 
Dante King's Avatar
 
Join Date: Jan 2005
Location: San Anselmo, California
Posts: 9,134
Default Re: Hot pixels? Please help me diagnose a problem with my Rebel XT

looks like a dirty sensor. If so its easily fixed by blowing (rocket blower or the like) or a cleaning outlined in many threads on this forum.
__________________
Dante
I am not an Lcoholic. Lcoholics go to meetings!

Gear List
Dante King is offline   Reply With Quote
Old 4th of April 2005 (Mon)   #3
ssim
POTN Landscape & Cityscape Photographer 2005
 
ssim's Avatar
 
Join Date: Apr 2003
Location: southern Alberta, Canada
Posts: 10,884
Default Re: Hot pixels? Please help me diagnose a problem with my Rebel XT

You've got yourself a case of dust bunnies. As Dante says, try the blower first and then you might have to clean your sensor. It is fairly straight forward and easy to do.
__________________
My life is like one big RAW file....way too much post processing needed.

Sheldon Simpson | My Gallery | My Gear updated: 20JUL12
ssim is offline   Reply With Quote
This ad block will go away when you log in as member
Old 4th of April 2005 (Mon)   #4
nater
Member
 
nater's Avatar
 
Join Date: Mar 2005
Location: Chicagoland
Posts: 201
Default Re: Hot pixels? Please help me diagnose a problem with my Rebel XT

Thanks for the advice. I have a dinky little brush blower, and I had tried blowing on the sensor (after removing the brush) to no avail. I just tried it again, more vigorously, and maybe 1/3 of the spots are gone. I guess I'll need to invest in an industrial-strength blower...
__________________
Canon 70D || Canon 10-22 f/3.5-4.5 || Canon 17-55 f/2.8 IS || Canon 24-105 f/4L || Canon 70-200 f/2.8L IS || Sigma 30 f/1.4 || Canon 50 f/1.4 || Canon 85 f/1.8 || Canon 60 f/2.8 Macro || Rokinon 8 f/3.5 fisheye
Feisol CT-3401N Tripod || Kirk BH-3 Ballhead
Buy & Sell Feedback: POTN || FredMiranda || ebay ~~~ Pro tip: Separate focus from shutter
nater is offline   Reply With Quote
Old 4th of April 2005 (Mon)   #5
eosster
Member
 
Join Date: Nov 2004
Posts: 473
Default Re: Hot pixels? Please help me diagnose a problem with my Rebel XT

Looks like a just a dust to me, time for a good clean up and good luck, you'll need it.
__________________
Canon EOS 60D | EF 50mm f/1.4 USM | Canon 430EX II
eosster is offline   Reply With Quote
Old 4th of April 2005 (Mon)   #6
hedphonz
Member
 
Join Date: Feb 2005
Posts: 86
Default Re: Hot pixels? Please help me diagnose a problem with my Rebel XT

i would think that there is also another problem that your camera is too small. jk. i would agree with everyone else that you have a case of the dust bunnies.
hedphonz is offline   Reply With Quote
Old 4th of April 2005 (Mon)   #7
robertwgross
Cream of the Crop
 
robertwgross's Avatar
 
Join Date: Nov 2002
Location: California
Posts: 9,462
Default Re: Hot pixels? Please help me diagnose a problem with my Rebel XT

That's sensor snot.

---Bob Gross---
robertwgross is offline   Reply With Quote
Old 4th of April 2005 (Mon)   #8
tim
Light Bringer
 
tim's Avatar
 
Join Date: Nov 2004
Location: Wellington, New Zealand
Posts: 49,334
Default Re: Hot pixels? Please help me diagnose a problem with my Rebel XT

You can purchase a kit to clean your sensor here. Many people have done it, and very few people have any problems. I do it myself, it took some practice to do it well, but it was easy. DO the practice swipe suggested, or a couple, to get the technique correct before trying on your camera.

If you're not confident, Canon I think clean sensors for free within their warranty period, and some stores may clean it quicker or while you wait even.

If the camera is brand new and you've not used it anywhere dusty, it's not unreasonable to return it and ask for a clean one, but you're not guaranteed to get one any better than your current one.
tim is offline   Reply With Quote
Old 5th of April 2005 (Tue)   #9
nater
Member
 
nater's Avatar
 
Join Date: Mar 2005
Location: Chicagoland
Posts: 201
Default Re: Hot pixels? Please help me diagnose a problem with my Rebel XT

Quote:
Originally Posted by WarrenO
blowing with your mouth is a very bad idea... all you need is spit on it and you have a much bigger mess.. get the right tools and you won't have issues. Did you just get this? (dirt) If so why is it so dirty? About the dead pixel...hmmm never even thought of that myself... I will check for that...

Thanks...

Warren
I didn't use my mouth. I used a cheapo blower that came in a camera cleaning kit, minus the brush.

And the camera is brand new -- I haven't even taken this one outside yet. I have no idea how it could be so terribly dirty.
__________________
Canon 70D || Canon 10-22 f/3.5-4.5 || Canon 17-55 f/2.8 IS || Canon 24-105 f/4L || Canon 70-200 f/2.8L IS || Sigma 30 f/1.4 || Canon 50 f/1.4 || Canon 85 f/1.8 || Canon 60 f/2.8 Macro || Rokinon 8 f/3.5 fisheye
Feisol CT-3401N Tripod || Kirk BH-3 Ballhead
Buy & Sell Feedback: POTN || FredMiranda || ebay ~~~ Pro tip: Separate focus from shutter
nater is offline   Reply With Quote
Old 5th of April 2005 (Tue)   #10
Toogy
"I like pictures of myself!"
 
Toogy's Avatar
 
Join Date: Nov 2003
Location: Ontario, Canada
Posts: 6,245
Default Re: Hot pixels? Please help me diagnose a problem with my Rebel XT

I'm curious as to what your aperture was when you took that shot?
__________________
Toogood Studios

Good Light and Shoot to the Right....
Toogy is offline   Reply With Quote
Old 5th of April 2005 (Tue)   #11
drisley
"What a Tool I am"
 
drisley's Avatar
 
Join Date: Nov 2002
Posts: 8,725
Default Re: Hot pixels? Please help me diagnose a problem with my Rebel XT

Simplest cleaning method.... Giottos Rocket Blower.
Those dinky little blowers just are not big enough.
As far as the hot pixel test goes, if you only have one at long exposures, that is a very good result
__________________

drisley is offline   Reply With Quote
Old 5th of April 2005 (Tue)   #12
nitsch
Goldmember
 
Join Date: Feb 2005
Posts: 2,393
Default Re: Hot pixels? Please help me diagnose a problem with my Rebel XT

I had this exact same problem when I got my 300D. The first ones sensor was filthy but otherwise the camera appeared to be brand new. I think some of them must just pick up more sensor crud than others during assembly. The marks were clearly visible from about f11 upwards so I returned it to the shop and asked for it to be swapped for another new one (although the sales assistant originally suggested they send it to be cleaned at my expense LOL! I don't think so!). The next one was a lot better but still not perfect when examined at about f32 however seeing as I'm never going to use this aperture in real life I decided not to let it bother me too much.

I have yet to clean the sensor but when the time comes I'm not too worried about doing it. I guess I have just accepted now that cleaning my sensor will have to become a routine maintenance task with a DSLR. It's just a bit of a shock to discover this issue when you move from film or point and shoot.
nitsch is offline   Reply With Quote
Old 5th of April 2005 (Tue)   #13
nater
Member
 
nater's Avatar
 
Join Date: Mar 2005
Location: Chicagoland
Posts: 201
Default Re: Hot pixels? Please help me diagnose a problem with my Rebel XT

Quote:
Originally Posted by Toogy
I'm curious as to what your aperture was when you took that shot?
I had set the camera to Tv. I just checked the pic, and it says the aperture was set to f/36. I'll do some tests at lunchtime to see how much shows up at wider apertures.

BTW - Based on the excessive dirt, and the hot/dead pixels, Dell has already agreed to ship me a replacement. And they didn't give me any hassle about it.
__________________
Canon 70D || Canon 10-22 f/3.5-4.5 || Canon 17-55 f/2.8 IS || Canon 24-105 f/4L || Canon 70-200 f/2.8L IS || Sigma 30 f/1.4 || Canon 50 f/1.4 || Canon 85 f/1.8 || Canon 60 f/2.8 Macro || Rokinon 8 f/3.5 fisheye
Feisol CT-3401N Tripod || Kirk BH-3 Ballhead
Buy & Sell Feedback: POTN || FredMiranda || ebay ~~~ Pro tip: Separate focus from shutter
nater is offline   Reply With Quote
Old 5th of April 2005 (Tue)   #14
drisley
"What a Tool I am"
 
drisley's Avatar
 
Join Date: Nov 2002
Posts: 8,725
Default Re: Hot pixels? Please help me diagnose a problem with my Rebel XT

Nater, odds are the next one you get will be just as bad or worse!
For an F36 picture, that is actually a fairly clean sensor. And having one hot pixel at more than 1 second is also very, very good.
You could go nitsch's route and demand return after return after return, but I think you would have to go thru the entire canon stock before you got a new DSLR with a completely dust free sensor, and without any hot pixels. In fact, I've read MANY stories of people exchanging their DSLR's because of 1 or two hot pixels at long exposures. Usually after going thru 3 or more cameras, they want the first one back because it had fewer hot pixels than the rest.
I don't think there is a single DSLR out there that won't show atleast 1 hot pixel on a 1+ second exposure.
And there definately isn't a single DSLR out there that doesn't have some dust on the sensor. And if there was, it would only take a few days of use before it did.
__________________

drisley is offline   Reply With Quote
Old 5th of April 2005 (Tue)   #15
Toogy
"I like pictures of myself!"
 
Toogy's Avatar
 
Join Date: Nov 2003
Location: Ontario, Canada
Posts: 6,245
Default Re: Hot pixels? Please help me diagnose a problem with my Rebel XT

I would bet that IF I took a picture of a wall at F36 I would have just as much dust if not more. But will I ever take a picture of a wall at F36?
I guess what I am saying is that if you start to notice it in 'normal' photographs, that is when you really have a problem.

PS, stop taking pics of your lens cap!!!
__________________
Toogood Studios

Good Light and Shoot to the Right....
Toogy is offline   Reply With Quote
Reply


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
please help diagnose my problem fgabriel Canon EOS Digital Cameras 18 1st of November 2006 (Wed) 14:31
Rebel XT - Hot Pixels Again - I think I hate dSLRs form Canon EOS Digital Cameras 32 10th of October 2006 (Tue) 02:43
Hot Pixels JBF Canon EOS Digital Cameras 22 22nd of January 2006 (Sun) 20:25
G2 problem: hot pixels in every shot Erie Canon G-series Digital Cameras 4 15th of May 2002 (Wed) 11:30
purple and green pixels, dead or hot pixels? socrates Canon G-series Digital Cameras 1 6th of August 2001 (Mon) 11:40


All times are GMT -5. The time now is 06:09.


Powered by vBulletin® Version 3.6.12
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
This forum is not affiliated with Canon in any way and is run as a free user helpsite by Pekka Saarinen, Helsinki Finland. You will need to register in order to be able to post messages. Cookies are required for registering and posting. HTML in messages is not allowed, plain website addresses are automatically made active by the board.