7D Grid Pattern Noise in boke midtones/shadows

M

mikeshu

Well-known member
Hi Guys,

So ever since I got my 7D in October and updated the firmware to the latest 2009 version (not yet the latest one), I noticed this strange grid pattern that seemed to be an artifact of the downsampling and not really the compression, since the artifacts remained static, as if part of the sensor.

The pattern appears in darker parts of the image or in areas out of focus (boke areas) and really stand out when ISO is bumped, but show up at ISO 320 and 640 as well. It's really only an issue indoors where a lot of darker areas are around. But what really gets me is the fact the ISO doesn't need to be that high for it to show.

Below is the link to the still grabs (100% crops):
http://picasaweb.google.com/117407426315702200232/7DGridPhenomenon?feat=directlink

The photos may lose some of the obvious grid pattern due to Picassa compression, but still show most of the heavy gridding. The ISOs range from 320 to 1600, and I think people can tell which ones are really cranked up :-) All footage shot at 1080p24 with a Tamron 17-50 VC 2.8 or an efs 17-55 2.8 IS, so it's not the glass.

I asked canon support if this was abnormal, and they say they see the grid pattern but it's not abnormal. I don't notice the issue from the other footage and stills I've seen so I want to see if other people noticed this as well, and if Canon is shrugging it off since they're a bit busy from NAB. I hope to be able to have the footage stand up to being projected on large screens, so figuring out if it is a flaw or not would be important.

All of your input is valuable!

Thanks to all!
 
I've had this happen as well. IF you have HTP enabled, try disabling HTP and test to see if the pattern is gone.
 
Fix patterned noise/banding is something that many CMOS sensors do in lightly colored underexposed areas.
 
Well HTP is off. I was just checking to see if this was abnormal at all. You guys all see this in your footage?
 
Few things:

1. Your images are underexposed. You need to light light light. Treat it like it is... a film camera.

2. People think they can shoot at high ISO's and make things look good. Just like film the higher the ISO the more the grain. (now the digital artifiacts) Realistially 1600 should never be thought of as an option unless you have no choice whatsoever. Try to get your ISO as low as possible but in that balance you must have enough light. I'm not saying overlight I'm saying light properly. Even if it's supposed to be a darker intimate scene you can still light for it. Hope this makes sense.

3. Compression will do this, it is there but the more light you can bring into your image the less you'll see it. I am not saying you cannot have contrast, I am saying that a contrastless image is a milky one and milky images is where this kind of artifacting will show up. So in the end don't blame the compression, work with it and know what it needs to help you bring a good image forward.

4. You will see this happen in you image is you push your gamma, brightness, or exposure in post production too high. Basically if you shoot too dark and later try to fix this you will see this.

5. Gradient shadows have this. It is there I have seen it. Going from a hotter spot to shadow. So be careful in post. If you slightly push the image you will see this pixalization so light as best as you can before going to post production. Interview footage is prone to this.

Is this a problem. Not really at all. In any format if you don't light properly you will see artifacts. Bottom line.
 
Yeah, I know these are examples of VERY bad lighting, but I shoot events and more used to the random noise that the CCD cameras show and not this fixed pattern noise. So I'm not exactly sure what is normal/abnormal with the patterns I'm seeing.

That being said, I think except for the super super noisy shots, most of them were shot around the 320-640 settings? I only use the native multiples of 160 as I learned from this awesome forum.

Thanks for all the insight, guys!
 
I too have experienced this draven. I did a lot of research and returned my camera to Canon and told them to calibrate it properly, providing visual proof of what I noticed. When returned, the problem was improved by a lot, but not perfect.

I have since returned it again to be calibrated once more. Anybody who tells you to light properly is dancing around the issue. At low ISO's, shadows shouldn't be producing that kind of grid banding effect, and Canon admits it. If you're interested to know more, feel free to PM me with what I did and how I spoke to them. I'll share my experience in detail for you.
 
Andrew Sisnett said:
Anybody who tells you to light properly is dancing around the issue. At low ISO's, shadows shouldn't be producing that kind of grid banding effect, and Canon admits it.
Click to expand...

Again, this is a well documented issue with CMOS sensors. While the Canon cameras haven't exhibited it much to my knowledge it is something that the sensors do. I buy that it can be made better by tweaks from Canon or is worse because something is wrong, but it's not something that "shouldn't be" happening.
 
Although a true phenomenon that exists, the question is, who is looking at your footage at that scale? We call this pixel peeping. It's fine to bring it up, but I wouldn't worry so much about how it affects your image.
 
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In still images, you could call it pixel peeping, but video framegrabs do not really tell the whole story. What you see in a single frame might look fine, but combined with 23 other frames per second, the result can really look like a bad banding/mosaic noise pattern effect that can be glaringly obvious. Depending on the level you see it, the effect is unacceptable in most applications. It depends on how well calibrated your camera is. Some reveal this much more than others.

In my case, and it looks like yours too, we got the short end of the stick. But Canon can correct it through an electrical adjustment (CMOS correction) as they called it on my repair slip.

I am sharing my experience with what Canon told me and that they in fact can correct the issue with proper calibration. While it might hold true that CMOS sensors do have some issue with this that is documented, it seems as if mikeshu and I have both experienced cameras that have more of it than others. I noticed this at LOW ISO(at 200 I said shouldn't see noise) and spoke to canon at length about it. They confirmed the cameras shouldn't be showing visible levels of noise at low ISO's, shadow's or not.

There are a ton of CLEAN 7D videos that properly demonstrate underexposed shadows and blacks. If your camera cannot perform up to that level then I recommend you certainly take in. It depends on how much is acceptable to you I suppose, but Canon seems willing to hold true to a high standard of excellence in their efforts to correct it with my camera.

You can take my word for this or not, but if in doubt, do some more research, talk to Canon and hear for yourself.

Kudos to Canon for helping me.

I hope this helps you.
 
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Andrew I know exactly what you mean about this type of banding. Funny, last night I was going to post a thread voicing my frustration about how unpredictable these cams can be at times. One minute (day) I can shoot some really nice footage and the next minute (day) I can shoot in the same room or under the same exact lighting conditions (same camera settings, lens…mostly ISO 320) and I get that same fixed pattern in lightly darkened areas (as you are talking about). I’ve shot with HTP on and off etc. in all scenarios but it’s like the camera has a mind of its own. What I’ve also noticed is that I have not seen this in my footage the first few months I had my 7D. Now…it just happens randomly. I’ve upgraded to the latest firmware (last night) so I have not tried to see if there was any difference as yet (actually I thought I did last night but it was late and I think my eyes were playing tricks on me while looking through the LCD). Anyways…you’re not alone in seeing this.


….as I type this response I’m wondering if this has anything to do with an overly heated sensor? I’ve never experienced that “overheat” icon like quite a few folks have but it does not mean that my camera’s sensor never got too hot. And you know Canon states that the picture quality might degrade when it does get hot…. Could this be an indicator of that? Who knows?
 
mr bill said:
Hi Andrew - was this Canon USA or Canon UK? My 550D is showing shadow noise even at 100iso.

thanks
Click to expand...

Are these dark dark dark shadows or are they white areas that are in shadow and are more than 3-stops under exposed?

Anyway, ISO is not the issue, exposure is.
 
Wow, a lot of response since I last visited. Thank you for all your input. Andrew, who did you talk to at Canon and how long did it take them to calibrate it?

Thanks a bunch, guys!
 
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