C100m2: Blue noise on top half of frame

[Glen Elliott]

Just picked up a C100m2. The first night testing it out I took it outside in a really dark environment and pushed it to 20,000 ISO. The overall noise is par for the course however the bluish noise/glow on the top half of the frame concerns me.

I've found the best way to see it is to be very underexposed at high ISOs (10,000 and up). When shooting at high ISO and your frame is well exposed it's difficult to see. Is this blue cast at the top of the frame normal?

[Gary Huff]

Yes. Why would you ever shoot/deliver in such conditions? Always expose properly.

[Glen Elliott]

That's not the question.

[Gary Huff]

Originally Posted by Glen Elliott

That's not the question.

Your question was answered in the very first sentence.

[Glen Elliott]

Thank you for the input. So you've seen this personally as well? You can push the ISO through the roof on other cameras and, as expected, get lots of noise, but not localized discoloration.

Btw I'm primarily an event shooter, so I can't say for certain I wouldn't run into a situation where I may need 10k ISO or more.

[Gary Huff]

Originally Posted by Glen Elliott

So you've seen this personally as well?

Yes.

You can push the ISO through the roof on other cameras and, as expected, get lots of noise, but not localized discoloration.

Not true. I have done this on other cameras, and there is definitely discoloration and nasty artifacting, especially when underexposing and then lifting in post.

Btw I'm primarily an event shooter, so I can't say for certain I wouldn't run into a situation where I may need 10k ISO or more.

I have needed to shoot 20,000 one time on a shoot for a client, and that turned out fine, not the greatest, but it looked far better than it had any right to. Most of the time I never have to go over 12,800. However, I also exposed properly. Any camera in which you significantly underexpose the image by an entire stop, and then lift that in post, with the added benefit of being way over the camera's native ISO rating, is going to exhibit a nasty look. You may luck out from time to time, but generally speaking, that is poor camera operation to do that.

I would look into picking up some f/2.8 zooms.

[Glen Elliott]

It's consoling to know you've seen the same phenomenon. I read elsewhere a gentleman had this issue exchanged the camera and the new one didn't exhibit this blue artifacting.

For reference I've previously shot on 5Dm3s for the previous 4 years. Regardless of the ISO it would never exhibit localized discoloration like this.

None of my lenses are slower than 2.8. This particular test was shot with a 50 1.2 @ 1.2. I wasn't proposing to shoot underexposed or to not use lighting. While torture testing the camera the first night I uncovered this flaw and thought it may have been a bad unit/sensor.

We always combine fast glass and off-camera lighting when necessary (dark reception venues).

[Gary Huff]

Originally Posted by Glen Elliott

It's consoling to know you've seen the same phenomenon. I read elsewhere a gentleman had this issue exchanged the camera and the new one didn't exhibit this blue artifacting.

I'd be interested to see what you are referring to explicitly. I wouldn't be too surprised if the issue wasn't quite the same.

For reference I've previously shot on 5Dm3s for the previous 4 years. Regardless of the ISO it would never exhibit localized discoloration like this.

You have previously shot the 5D Mark III at super high ISOs and underexposed by a full stop?

[Glen Elliott]

Originally Posted by Gary Huff

I'd be interested to see what you are referring to explicitly. I wouldn't be too surprised if the issue wasn't quite the same.



You have previously shot the 5D Mark III at super high ISOs and underexposed by a full stop?

I have a picture for reference in the original post. Blue artifacting/noise in the top of the frame, a bit worse on the right.

The 5D3 pushed a similar way wouldn't exhibit this localized discoloration.

[Gary Huff]

Originally Posted by Glen Elliott

I have a picture for reference in the original post.

I am not referring to your OP, I am referring to you saying you "read elsewhere" of a similar issue solved by exchanging the camera. I would like to see that thread.

[Noa Put]

Originally Posted by Glen Elliott

Is this blue cast at the top of the frame normal?

Beside the fact that you can expect artifacts at these high iso's this doesn't look normal to me. Just to rule out a lens issue, does this also show up in the same way with another lens?

[Seth Bloombaum]

***Have you black-balanced?***

Were it me, I'd want to shoot additional tests. Though the dark background in the supplied image *looks* uniformly unlit, top to bottom, it may not be. As we get down below 10 IRE, I wonder if there may be a subtle lighting gradation there which may be invisible to the eye, but not invisible to the camera's image processing.

For example, a black restore function in the noise reduction processing could produce a look like this with the lower half of the image's blacks being below a clamping point, and the upper half of the image being above the cutoff. Hypothetically, since I don't know if the cam uses black restore. You need a uniform scene to test.

I'd shoot such tests with the various image enhancements turned off, like maybe the EOS Standard preset.

I don't have any experience on the M2, but, if it were my camera, *any* camera, and I could reproduce this at will, it would be going back to Canon. Given equal luminance, noise should be even, even down there in the mud.

[Glen Elliott]

Originally Posted by Gary Huff

I am not referring to your OP, I am referring to you saying you "read elsewhere" of a similar issue solved by exchanging the camera. I would like to see that thread.

The thread wasn't on DVinfo so I'll PM you the link.

Originally Posted by Noa Put

Beside the fact that you can expect artifacts at these high iso's this doesn't look normal to me. Just to rule out a lens issue, does this also show up in the same way with another lens?

I thought it looked odd too. I had a friend with the camera use high ISO and purposely underexpose the image (the best way to see this phenomenon) and his camera did the same thing. Even down to the localization (top of the frame, worse on the right side).

Originally Posted by Seth Bloombaum

***Have you black-balanced?***

Were it me, I'd want to shoot additional tests. Though the dark background in the supplied image *looks* uniformly unlit, top to bottom, it may not be. As we get down below 10 IRE, I wonder if there may be a subtle lighting gradation there which may be invisible to the eye, but not invisible to the camera's image processing.

For example, a black restore function in the noise reduction processing could produce a look like this with the lower half of the image's blacks being below a clamping point, and the upper half of the image being above the cutoff. Hypothetically, since I don't know if the cam uses black restore. You need a uniform scene to test.

I'd shoot such tests with the various image enhancements turned off, like maybe the EOS Standard preset.

I don't have any experience on the M2, but, if it were my camera, *any* camera, and I could reproduce this at will, it would be going back to Canon. Given equal luminance, noise should be even, even down there in the mud.

I did a black balance because I was unhappy with the green hue the camera was giving me (in all custom preset settings). It helped a bit but didn't fix it. I found I needed to move the custom white balance dot two notches down toward magenta to neutralize the stock green cast.

This still was shot after the black balance was done. Granted I wouldn't be shooting in such dark conditions with such high ISO however it was the first night with the camera and I wanted to torture test it a bit to get a feeling of it's limitations.

This appears to be a known issue at high ISOs on the C100's.

[Gary Huff]

It's ultimately up to you if you want to send it back and see if you get one that doesn't exhibit this, however I wouldn't be surprised if the reports that new units didn't exhibit the problem were based on tests done right after getting the unit and redoing them now would exhibit the same problem. The link you sent me had a user who had more problems than just a blue streak after underexposing AVCHD by a stop even at 40,000 ISO and raising it in post.

[Glen Elliott]

Picked up 2 more (gotta love big rebates) so I'll be able to compare, though I'm pretty confident it's going to be the same on all 3.