Picture taken with the lens caps on, ISO = 400, exposure = 1", has red dark specks of 3x3px size

[sergey_adamenko]

Hi All!

 

Two weeks ago I get my new CANAON EOS DIGITAL REBEL XT 350D.

 

Accidentally a made a shot with the lens caps on.

The last picture should be black, but, to my surprise, there was a

group of dark red specks in the image.

 

I did more images with different ISO/exposure settings (RAW format),

but the speck group didn't disappeared.

Its appox. size is 3x3px.

 

The non-black pixels are arranged in the following way:

1-2-1

2-3-2

1-2-1

 

where "3" means the brightest pixel, and "1" means the dart-dark red

one.

 

I was thinking it could be defective sensor, so I contacted the

support. They recommended me to send the camera

to one of theirs support centers "...to be examined...". .

Now I want them to look on the pictures because don't want to send

the camera unless I'm sure the problem is

with the sensor and they agree on it.

 

And the reason I'm writing to the conference is, that maybe someone

has had such issues and he/she could

share the experience... It also will be interesting if someone will

test his/her camera in the way I did.

 

I have my images uploaded and they are available on Inet:

 

1. Picture taken with the lens caps on, ISO = 400, exposure time =

1"

http://www.mysharefile.com/v/2957648/img_2911.cr2.html

 

 

2. Picture taken with the lens caps on, ISO = 400, exposure time =

10"

http://www.mysharefile.com/v/8143079/img_2910.cr2.html

 

 

3. Picture taken with the lens caps on, ISO = 1600, exposure time

= 1"

http://www.mysharefile.com/v/7246556/img_2912.cr2.html

 

I also can post my correspondence with the support if interested.

 

 

Thanks,

Sergey Adamenko

Houston, TX

[zacker]

COULDNT DOWN LOAD AN IMAGE... could be noise.. at ISO 400 you will get some noise.

-zacker-

[PuppyDigs]

Is it noticeable in images with the lens cap off? If not, don't worry about it. Most sensors

show a few hot, stuck or dead pixels with long exposures of the back of lens cap.

 

Also, you might want to pixel peep at 100-400% along the edges of the frame to make

sure your lens is tack sharp.

[ccrider]

HI Sergey

 

I had a similar problem with my 5D. I had a group of hot pixels showing up in one location. Useing a test similar, taking a photo with my lens cap on and using a shareware test to find out how many hot or dead pixels I had. Sorry I do not remember the name of the shareware, but on some of the canon forum websites you should be able to obtain it. It was more pronounced at the higher ISO but was still their in the lower ISo's as well. I have a canon repair center near my house, they re-mapped the sensor, not sure what that means. but the problem was fixed. Received the camera back within 10 days and have not had any problems. I hope that helps some. Chuck

[sergey_adamenko]

Thanks for the answers, guys!

 

I'm sure a 3x3 picture on real images will not be a concern. But we always want get

the best from a manufacturer. I also understand that none on the market has perfect technology and there

are some limitations of quality of sensors. But there is no word about possible "dead" pixels on the sensor in the manual.

Thought there is a phrase about "dead" pixels on the LCD.

 

To decide whether to send the camera to a service center I need to compare my "test" image with

some others taken with EOS 350 TX.

 

Please send me images in RAW format.

 

 

And... I just tried to download from http://www.mysharefile.com/v/2957648/img_2911.cr2.html. It works. None, you have to wait 15 sec before the download url will appear on the page.

I also can send the pictures by e-mail.

 

 

Thanks,

Sergey

 

E-mail: zergey.awamenko@zcgo.com.

 

To send me e-mail, please compose the real e-mail address: change all "z" to "s", all "w" - > "d". Thanks again.

[bobatkins]

It's a hot or stuck pixel. Just one pixel, the surrounding pixels are probably the result of bayer interpolation of the image data.

 

Most sensors show them if you look hard enough.

 

Maping them out just means turning them off and interpolating around them. They aren't there anymore and you lose that "bit" of information, but you'll never notice. What's one pixel among 8 million others!

[sergey_adamenko]

The scaled image is produced from RAW source image, just scaled. I thought that raw image is the real raw - no interpolation or another manupulation.

[phule]

If you had set the exposure to longer than 1 second and turned on the noise reduction function, the camera would have taken a second exposure with the shutter closed and then subtracted the noise from the first that would (in theory) leave you with a perfectly black frame.

 

It might be an interesting experiment to do this to see how effective the dark-frame subtraction really is.

[sergio_sepulveda]

What Bob Atkins said, My d300 also have one "special" pixel, with more in-camera sharpening its presence is spread to the adjacent pixels. Higest ISO makes it even worse. I correct that with PS healing tool if the photo is to be croped and/or enlarged . I can live with that.

Best Wishes

 

Sergio

[jo7hs2]

Interestingly, my 350D also exhibits two colorful spots, one red, one blue on the right side of the frame on long exposures. That in itself didn't intrigue me, I expected hot pixels, I get plenty of little white ones on very long exposures. What did intrigue me is that the colorful spots occur even after the long exposure correction (in camera) has been used. Based on the size and placement, as well as a tendency to only appear in night shots (not even on black background during the day) I am almost suspicious that the two dots are coming from somewhere inside the camera other than the sensor, but that is just my paranoia showing.

[bobatkins]

<em>I thought that raw image is the real raw - no interpolation or another manupulation.</em>

<p>

You can't view a RAW image. That's a common misconception. In order to view it you MUST deconvolute the Bayer matrix or you simply won't get an image. The Bayer deconvolution alters the data, that's the whole point!

[ccrider]

The group of hot pixels that were present with my 5d was something I could not accept, especially with the amount of money I spent for the camera. The red cluster in the same exact spot was visible in all of my photos especially where there was alot of shadow detail. In my case I decided to send in to be mapped out. So you have to ask yourself if it is so noticeable that you need to clone or patch it out, that it might be worth it to send in to be fix. I assume under warranty at no charge. good luck chuck

[sergey_adamenko]

Thanks for your answers, guys!

 

I've read about mapping.

Wish Canon provided a tool in to mark hot pixels, so that clients

can resolve such issues yourselves.

 

 

Sergey.

[jason_kulas]

<i>>Wish Canon provided a tool in to mark hot pixels, so that clients can resolve such

issues yourselves.</i>

<br><br>

It would be nice if all RAW conversion s.w. (Canon's, Adobe's, DxO's, etc) could either

automatically find these and interpolate them or let you mark them to interpolated

forevermore.