I see noise bands in my 5D shadows. Is this normal?

I have noticed that the noise I see in the shadows of my 5D isn't random. Instead it has a definite pattern to it. The pattern shifts subtly from image to image which makes it hard to filter out. Moreover, it is distracting in a way that pure white noise is not. To highlight this effect, I took an image with the lens cap on and then in ACR pushed the settings

ISO 800

exposure +4

shadows 0

brightness +50

contrast +25

I am not suggesting that anyone process real images this way. I am just trying to show clearly the effect I am talking about. Is my camera unusually noisy, or is this common? BTW, I see the same sort of banding at ISO100, so it is not limited to high ISO images.

I had a problem w/ my 5D sensor. It had a black line of dead pixels in all the photos. This was after about 6 mos of use. I sent it to Canon repair and they did a full repair and tune up and sent it back for free. That took about a week.

That's what I suggest you do. You can include a CD with the above photo on it for them. That's what I did w/ one of my images.

Cheers

James

Thanks James. That is a good suggestion, but before I send it back, I am curious about whether this really is anomalous. It might just represent the normal unit to unit variation. Perhaps someone else with a 5D could repeat this measurement to see what they get. Normally I wouldn't stress over this too much but I see these patterns in the shadows, even at ISO100. They aren't as dramatic as in the image I posted, for which I pushed the controls to the extremes to highlight the issue.

Hi Steve. Mine does that too. I had a pic of two sheepshead doing that open mouthed threatening thing at each other, but of course the strobes were completely set wrong so the shot was like 4 stops underexposed at least). When I cranked it up trying to save it a little, I saw the same fabric like pattern. It isn't visible in most shots though, only when you really crank the exposure in post. And you're right, the noise isn't random, it looks like fabric.

Susan

Hi Susan. It sounds like this is endemic to the design, but it begs the question of how much is too much? Perhaps you could take a dark image for comparison. I took another one without a lens attached at ISO 100 and 1/8000th and got the following. It is virtually identical with the exception of the light areas in the corners.

Steve,

I'm not an expert on this, but not sure if this is something to worry about. When I do similiar tests against a white background to check for dust on my 400D sensor, I get similiar patterns when I up the exposure to find those little dustballs.

+4 exposure is a pretty extreme adjustment.

Not a 5D, but a 20D. I can only reproduce the effect at 3200 ISO. here the bands are horizontal, not vertical as in your images. All other images are just black. I included a link to a 1600 iso image as well.

http://img.photobucket.com/albums/v386/gwi...se-ISO-3200.jpg

http://img.photobucket.com/albums/v386/gwi...se-ISO-1600.jpg

PS: on my screen and uploaded, the image looks slightly less banded. Could it be a jpg artefact as well.

This banding is inherent in the EXTREME shadows of current dSLRs. In 'normal' use you shouldn't notice it, but when using severe adjustments it may appear - the cause is overadjustment of the image file - trying to achieve a result from an image which was either incorrectly exposed (for the result you want) or at the extreme limit of the camera's capabilities. I'm sure that issues like this will become substantially less as dSLRs evolve but in all honesty they are usually noticed only by examining files very closely and shouldn't give cause for concern (all 3 of my 1DS cameras show varying patterns in extreme shadows if pushed too hard).

+4 exposure is a pretty extreme adjustment.

Agreed. The only reason for the +4 exposure is to unambiguously highlight the issue. Clearly, the banding is much less severe at lower exposure adjustments. However, you can see it with as little as +0.5 to +1.0. From the responses I have gotten, it seems to vary a lot from camera to camera, which brings up the original question, how much is too much?

Maybe a real example would help. Here is an image for which I pushed the exposure by +0.85.

If you zoom in on the lower left you can see the patterned noise in the background. It is small but noticeable. If it was random, it wouldn't be a big deal, but the pattern bothers me. Maybe I am just expecting too much from my camera, but I think that it should be possible to subtract much of it away by using a technique similar to what the camera does for long exposures.

BTW, I noticed in my original post, I made a typo. The dark noise images I posted were brightness +150 not +50. What a difference a digit makes.

Steve,

I tried to replicate your ISO 800, +4 exposure shot with lens cap on and got a very boring image. No features at all except a couple of slightly hot pixels. I think you need to send your camera in.

Also, I've pushed up the dark parts of some of sunballs shots I've posted earlier by probably more than 2 stops using curves and didn't see anything near as bad as your dolphin tails.

Steve - What AF mode were you in? I remember there being some discussion on the web that a few 5D cameras were exhibiting banding when using AI Servo...

I agree that a trip to Canon couldn't hurt, however.

What AF mode were you in? I remember there being some discussion on the web that a few 5D cameras were exhibiting banding when using AI Servo...

Just tried again with AI Servo and got the same black result.

I am aware of the AI servo problem so to forestall it I took images WITHOUT a lens. (No lens, no focus mode) I got the same result as with a lens installed with the lenscap on. The results are the same at high ISO and low ISO. They are the same for 1 sec and 1/8000sec. My guess is that it is pickup in the video amplifiers. I think you are right. I am going to send it to Canon for eval.

BTW, for a direct comparison to the images I posted you need

exposure +4

shadows 0

brightness +150

contrast +25

BTW, for a direct comparison to the images I posted you need

exposure +4

shadows 0

brightness +150

contrast +25

Those were the settings I used on photoshop CS2. The raw file is here:

http://herbko.net/misc/IMG_4410.CR2

if you'd like to have a look.

All 3 of my 1DS cameras show VARYING signs of noise patterning in the deep shadows (though none impinges on real images). I'll be interested to know if Canon say that your 5D is within tolerance or otherwise - I'd suggest sending a 'real world' image (such as the dolphins) in with it as I wouldn't mind betting that they get an awful lot of heavily adjusted images showing 'faults' which they probably consider to be somewhat different to those from the reality of actual use. Do keep us posted on this.

Steve,

You might have a look at this website:

http://www.ddisoftware.com/20d-5d/

A guy found that his 5D was doing something that sounded like what yours is doing. Here is a quote:

"Imagine my surprise when I take my 5D out of the box, hook everything up, and begin my technical testing only to find that the 5D is returning numbers that make it look like a bit of a lame duck compared to the 20D that I'm running side-by-side. After many hours of testing and trading photos with others in some online forums, I find that my first 5D is defective! To make a long story short, my initial 5D had subtle pattern noise that you had to zoom in to see, but was visible in literally every shot. I tried different lenses, different memory cards, and different settings just in case, but no luck. No matter what I did, I got the same underlying 4x4 noise pattern. The noise manifested itself visually as either banding or a "burlap" appearance that was visible in lighter colors and could be seen at 1:1 zoom on screen in every shot if you knew where to look."

The "burlap" comparison is what really keyed me in to the potential similarity to your issue. He returned it and got a new one that was fine (see rest of the text at the site).

Mike