There's something in my images, please help

[chrisortenburger]

Just bought my first digital SLR from B&H (350 D) and I am noticing weird red clusters of pixels in my images. (Especially with long exposures). I have checked the lens throughly and it is free from any dust or debris. The camera has less than 300 images shot through it so I can't think it would be the sensor. Wouldn't dust appear black?

I've read a little about hot pixels. Is this normal? Is my camera defective?
Any advice on what to do would be greatly appreciated.

http://eyenovation.com/forums/other/example_01.png

http://eyenovation.com/forums/other/example_02.png

Here is an image right off the camera
Link: http://eyenovation.com/forums/other/IMG_0568.JPG

[EpHeSuS]

Hot pixel, quite normal on long exposures. If you can see it on short ones ( like under 1 sec) I'd take it back to Canon.

[Mitcon]

As said this does happen with long exposures, try turning on the noise reduction for long exposures or clone them out when PPing. If it's a real problem for you and the other options don't please you talk to Canon to see if they can map it out for you. Given time though I think with all digital cameras with use they will get more hot or dead pixels.

[chrisortenburger]

Hot pixel, quite normal on long exposures. If you can see it on short ones ( like under 1 sec) I'd take it back to Canon.

Here is what I am seeing on a typical shot w. no long exposure:

http://eyenovation.com/forums/other/100percent.png

http://eyenovation.com/forums/other/specs.png


Is this normal, or am I in possession of a bum unit?

[EoSD30fReAk]

take it back! you shouldn't see hot pixels above 1 second exposures.

it's not good to see dead pixels with an exposure of 1/60 second.

[chrisortenburger]

*sigh* I am out of my B&H Photo / Video 14 day warranty. This may be beyond the scope of the question, but I take it that I'm screwed? Should I proceed by calling Canon?

[EoSD30fReAk]

it can happen with every digital so i guess you're just unlucky this time.

the best thing to do is call canon and they will probably ask you to send it in for repair.

[mdude85]

I don't think it's a hotpixel. Look at it -- it's a collection of pixels of varying degrees of color, it's not one single pixel as most hotpixels tend to be. It is something weird though. you should get some second and third opinions somewhere.

[robertwgross]

I don't think it's a hotpixel. Look at it -- it's a collection of pixels of varying degrees of color, it's not one single pixel as most hotpixels tend to be. It is something weird though. you should get some second and third opinions somewhere.

It could easily be from one single hot pixel. Then, if you think about the way JPEG works, you will understand how the image looks this way.

---Bob Gross---

[elbirth]

I don't think it's a hotpixel. Look at it -- it's a collection of pixels of varying degrees of color, it's not one single pixel as most hotpixels tend to be. It is something weird though. you should get some second and third opinions somewhere.

It could easily be from one single hot pixel. Then, if you think about the way JPEG works, you will understand how the image looks this way.

---Bob Gross---

Exactly, he blew the image up to 600%. At 100%, you'll notice that 1 screen pixel will equal 1 image pixel. Beyond that, the screen is having to enlarge them past the 1:1 ratio, giving you the "collection of pixels" look. Look back at the original image directly off the camera and you'll see that it is indeed a single pixel.

[Rokkorfan]

Send it in to Canon for warranty repair, they will map it out and you will have it back promptly. This is not a big deal - most sensors have them, people just don't realise because they are mapped out before delivery.

[Simon Spiers]

My 20D does the same thing if you turn the iso up to 800 and expose for 5 seconds or so without noise reduction.
So what!

[chrisortenburger]

My 20D does the same thing if you turn the iso up to 800 and expose for 5 seconds or so without noise reduction.
So what!

Look at the settings I used. ISO 100, 1/60th of a second. :(:(

[mdude85]

Exactly, he blew the image up to 600%. At 100%, you'll notice that 1 screen pixel will equal 1 image pixel. Beyond that, the screen is having to enlarge them past the 1:1 ratio, giving you the "collection of pixels" look. Look back at the original image directly off the camera and you'll see that it is indeed a single pixel.

Each square is one pixel, even when zoomed in. To prove this, simply go into Photoshop or another image editor and choose a brush that is one pixel in area. Then mark the canvas with one click. The image will be one pixel large and one pixel wide.

http://img334.imageshack.us/img334/1876/onepixel0bx.jpg

When the user "resizes" an image, then, yeah, one red pixel will appear as more than one. the OP should show us a "zoomed in" view rather than a "resized view."

I understand the mechanics of JPEG compression and robertgross has a point, BUT I shoot JPEG all the time and sometimes see hotpixels on a small Nikon P&S that I own. Even in that camera, a hotpixel tends to show up as one or two pixels, maybe 3 at the most. This person must have conducted some major JPEG compression to get a hotpixel that when compressed contains so many compression artifacts. In fact, many times, since pixels are square, they do not show many artifacts when they are compressed. Often times, only rounded edges do. To me it just doesn't seem like a hotpixel, but it sure is weird. Plus, usually we don't see hotpixels on such short exposures.

This page might prove to be a good resource.

http://webpages.charter.net/bbiggers/DCExperiments/html/hot_pixels.html#

[Longwatcher]

I was trying to figure it out until I noted as someone pointed out the pixel was enlarged 600 times, and probably used an interpolation algorithm when doing so. the expansion of the single pixel is not consistant with jpeg compression which does so in a 8x8 pixel square. It is indeed a single pixel. If enlarged with out interpolation it would most likely just be a red square.

As to it being normal. Consider that we are talking an 8 million pixel sensor. when the sensor was put on the camera it probably had 8-16 bad pixels that were mapped out before shipment, this is normal and to reduce this would significantly increase the cost of the sensor. Over time (as in years) more will show up and there is very little, short of having the camera remapped, that you can do about it. Except that it is usually easier to just clone or heal out the bad pixel when it gets in the way, I personally think the camera software needs to come with a remapping tool , except I can see people doing it everytime the have an anomolous pixel, which would not be the right thing to do. Even the really expensive high-tech sensors I work with have bad pixels that have to be mapped out. we are usually happy with a 99.9% good pixel rate. (That would be 800 pixels on of your 8MP camera)

Although there is a small chance that the pixel may heal itself with time, if it bothers you significantly then contact Canon repair and they should be able to remap the sensor to hide the bad pixel (it will still be there, you just won't notice it any more.

On my 16.5 MP camera I have two annoying green pixels at fast shutter speeds and several red pixels and a couple of blue at long duration shots that show up, since the green pixels usually hide themselves I don't worry about them and I only rarely shoot at long duration so am not bothered by the red pixels much. This all said, I already intent to send my camera to Canon before the warranty runs out to have them remapped. I am just waiting because I know I may lose one or two more before then and I only want to part with my perfectly good camera once.

Just my experience and opinion,

[mdude85]

I was trying to figure it out until I noted as someone pointed out the pixel was enlarged 600 times, and probably used an interpolation algorithm when doing so. the expansion of the single pixel is not consistant with jpeg compression which does so in a 8x8 pixel square. It is indeed a single pixel. If enlarged with out interpolation it would most likely just be a red square.

As to it being normal. Consider that we are talking an 8 million pixel sensor. when the sensor was put on the camera it probably had 8-16 bad pixels that were mapped out before shipment, this is normal and to reduce this would significantly increase the cost of the sensor. Over time (as in years) more will show up and there is very little, short of having the camera remapped, that you can do about it. Except that it is usually easier to just clone or heal out the bad pixel when it gets in the way, I personally think the camera software needs to come with a remapping tool , except I can see people doing it everytime the have an anomolous pixel, which would not be the right thing to do. Even the really expensive high-tech sensors I work with have bad pixels that have to be mapped out. we are usually happy with a 99.9% good pixel rate. (That would be 800 pixels on of your 8MP camera)

Although there is a small chance that the pixel may heal itself with time, if it bothers you significantly then contact Canon repair and they should be able to remap the sensor to hide the bad pixel (it will still be there, you just won't notice it any more.

On my 16.5 MP camera I have two annoying green pixels at fast shutter speeds and several red pixels and a couple of blue at long duration shots that show up, since the green pixels usually hide themselves I don't worry about them and I only rarely shoot at long duration so am not bothered by the red pixels much. This all said, I already intent to send my camera to Canon before the warranty runs out to have them remapped. I am just waiting because I know I may lose one or two more before then and I only want to part with my perfectly good camera once.

Just my experience and opinion,

I respectfully disagree that this red thing is one single pixel. You can tell just by looking at the 100% crop that it is not a single pixel, but rather a mass of red pixels that is bright in the center and fades from red to black as the radius increases. That is quite obvious. It almost looks like some sort of piece of red dust on the sensor. The OP needs to show us a "zoomed in" version of the photo, not a resized version. For instance, here is a version of the 100% crop at 600% magnification (no resize). Each red square is one pixel.

http://img296.imageshack.us/img296/2382/600percent9hu.jpg

I mean, this thing could definitely be some sort of sensor defect. But a hotpixel, in the most strict sense? I don't think so.

OP, did you take the same picture with a different lens, and if so, what did you see?

[badrotation]

I respectfully disagree that this red thing is one single pixel. You can tell just by looking at the 100% crop that it is not a single pixel, but rather a mass of red pixels that is bright in the center and fades from red to black as the radius increases. That is quite obvious. It almost looks like some sort of piece of red dust on the sensor. The OP needs to show us a "zoomed in" version of the photo, not a resized version. For instance, here is a version of the 100% crop at 600% magnification (no resize). Each red square is one pixel.

http://img296.imageshack.us/img296/2382/600percent9hu.jpg

I mean, this thing could definitely be some sort of sensor defect. But a hotpixel, in the most strict sense? I don't think so.

OP, did you take the same picture with a different lens, and if so, what did you see?


Think about it this way..... it could be one hot pixel, that is in turn heating up the surrounding pixels, thus making it look brightest in the middle, and fading away the further out you get from the center of the bunch.


I am guessing however it is a single pixel, and the jpeg compression is causing the fading effect.

[mdude85]

Think about it this way..... it could be one hot pixel, that is in turn heating up the surrounding pixels, thus making it look brightest in the middle, and fading away the further out you get from the center of the bunch.


I am guessing however it is a single pixel, and the jpeg compression is causing the fading effect.

This rarely happens, because hot pixels are simply charge leakages. Charge doesn't leak from one sensor to another. If they did, there would be no way to take a picture because every photosensor on the CCD would have an effect on every other sensor. Each photosensor is unique.

If the JPEG compression was causing the fading effect, the composition would basically look like this:

1 bright red pixel, 1 pixel wide by 1 pixel high
8 much darker red pixels, 1 pixel wide by 1 pixel high, forming a square around the 1 red pixel.

[mdude85]

This is a GIF image of 1 red pixel at 1600% magnification (no resize)

http://img348.imageshack.us/img348/554/pixeltestgif5gr.gif

Here is an image of a red pixel that has been saved as a JPEG with 100% artifact recovery (effectively 0% quality loss). As you can see, there is still tremendous quality loss, but the red pixel doesn't even begin to resemble what the OP sees on his images.

http://img348.imageshack.us/img348/9344/pixeltest39ly.jpg

As you can see, there is a bright pixel in the middle with one perimeter square of faded pixels on the exterior (you might need to adjust the brightness on your monitor)... none of this elliptical stuff you see in the OP's picture.

There would need to be multiple hotpixels clumped in a group to get this kind of pattern the OP sees, and this never happens. Does the OP have a RAW sample he can show?

[chrisortenburger]

OP hereBefore I send the camera back to Canon for repairs, I can help anyone here by snapping more photos. Any one that wants to suggest a shot to take, I gladly will.
Needless to say I just want to rid myself of the cluster. One pixel in a 4 meg file would be no problem to clone, but the problem is bigger than one pixel, I'm afraid.

[mdude85]

OP hereBefore I send the camera back to Canon for repairs, I can help anyone here by snapping more photos. Any one that wants to suggest a shot to take, I gladly will.
Needless to say I just want to rid myself of the cluster. One pixel in a 4 meg file would be no problem to clone, but the problem is bigger than one pixel, I'm afraid.

Take a RAW photograph so we can dispel this "JPEG compression artifact" myth once and for all.

[chrisortenburger]

Here is a raw file. Oddly enough I can't see the hot pixel as red. I see one brighter white pixel where it should appear... Strange.

http://homepage.mac.com/chrisortenburger/downloads/IMG_0596.CR2.zip

[booggerg]

Just to rule out any lens flare etc.. Take a picture in RAW with your lens cap closed...

[chrisortenburger]

Just to rule out any lens flare etc.. Take a picture in RAW with your lens cap closed...

Okay, but what at settings ? Long Exposure?
Does it matter?

[elbirth]

Okay, but what at settings ? Long Exposure?
Does it matter?

just use the same settings you use in any picture that usually gets the effect... if you want to really be sure, take a short exposure, medium length exposure and a long exposure and check them out.

[chrisortenburger]

Okay here is the image:

http://homepage.mac.com/chrisortenburger/downloads/raw_file.zip

I am noticing it on the JPEG, but not the RAW file. That's is very odd to me. Can anyone explain?

http://www.eyenovation.com/forums/other/raw_jpeg.png

[jfrancho]

If it were a "hot pixel" I'm sure it would show in the raw file. Even when converted to a jpeg, there is no evidence of the "red spot." Sounds like either way you should take it back.

[mdude85]

Well, THAT is something isn't it? Quite strange. Seems like perhaps it's an error with the JPEG compression algorithm. Maybe you should reinstall the firmware, or you could take it back. Either well you'll be without your camera for a little while. I've never returned a camera before, so I don't know how much of a hassle it is to get a new one.

[jfrancho]

I wonder if you change the jpeg compression if the "Red Spot" moves. Also, does the spot show just in raw+jpeg, or also in jpeg? This could become a wild goose chase, though. He should probably take that camera back asap.

[Longwatcher]

The explanation for the sopt showing in the in-camera developed jpeg and not the RAW converted-in-computer jpeg is the software doing the interpolation of the BAYER sensor data is different. If you have another RAW conversion program to try I would be interested in seeing if it also shows in that conversion or not. However as long as it keeps popping up in the same spot you do have a bad pixel(s). If it is annoying send it back.

On a trivia note: I have noticed that some LCD monitor manufacturers and retailers are using a 8 pixel defect policy. If less then 8 pixels are bad they will not take it back. The camera guys may start this eventually as well. So I wouldn't wait too much longer.

[jfrancho]

The explanation for the sopt showing in the in-camera developed jpeg and not the RAW converted-in-computer jpeg is the software doing the interpolation of the BAYER sensor data is different. If you have another RAW conversion program to try I would be interested in seeing if it also shows in that conversion or not.That makes senes. I don't know what Chris was using, but I used ACR 3.1, and there was no spot.

[Keiffer]

I heard if you put your lens cap on and set your cam to fire repeatly and the problem might go away.