Zebra Issue on 4K Production Camera

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David Chapman

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Zebra Issue on 4K Production Camera

PostTue Apr 15, 2014 2:06 am

Is anyone else having issues or problems with zebras set to 100% on the 4k Production Camera? My camera has been working flawlessly until today. Zebras set to 100% now only appear in the upper corners of the image on the LCD, even though the whole image is overexposed. The iris button still steps down the aperture to avoid clipping, but the zebras don't display appropriately.

I do see zebras over the whole screen when below 90%.

This is a shot where the sky above the fence is over exposed, but the screen only shows zebras in the top corner.
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Re: Zebra Issue on 4K Production Camera

PostTue Apr 15, 2014 2:23 am

Upon further discovery, when record is set to Video, zebras show areas that are clipping the sensor. When switched back to Film mode, the zebras go away except for the outer corners. See the image below. The only difference is record mode is set to Video vs Film.

I tried ProRes HD instead of 4K to see if it made any difference

I also toggled the display to Video instead of Film when recording Film without success.

Am I going crazy?

Image
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Re: Zebra Issue on 4K Production Camera

PostTue Apr 15, 2014 2:34 am

I dropped the zebras down from 100% to 95% and more of the zebra pattern shows, but it's missing a good portion of the center. This looks odd, right?

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Re: Zebra Issue on 4K Production Camera

PostTue Apr 15, 2014 4:23 am

I've had 3 BMPC4k cameras and they've all behaved differently. The one I have now won't display zebras unless I'm below 85. Also the "Iris" button will only adjust the aperture up and down and won't automatically set for peaks like it's supposed to. But I just stare at the FPN and hot pixels it makes me forget about the little problems like F-ed up zebras :)
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silvio bonomi

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Re: Zebra Issue on 4K Production Camera

PostTue Apr 15, 2014 5:22 am

....and another big problem with zebra in 4k production camera: Zebra area extension NOT CHANGE at different ISO remain always the same.Only Iris variation change area extension that is overxposed!!.

silvio bonomi
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adamroberts

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Re: Zebra Issue on 4K Production Camera

PostTue Apr 15, 2014 6:16 am

silvio bonomi wrote:....and another big problem with zebra in 4k production camera: Zebra area extension NOT CHANGE at different ISO remain always the same.Only Iris variation change area extension that is overxposed!!.

silvio bonomi


Like the BMCC and BMPCC, the zebras are based on sensor clipping and not ISO.
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silvio bonomi

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Re: Zebra Issue on 4K Production Camera

PostTue Apr 15, 2014 6:49 am

Sorry Adam but I not understand...in ( all) other cameras when you apply a gain (or iso level changes...) overexposed area change. How is possible to have a reference limit if the limit is, for example, 90% and if the area of zebra not change, at variations, of ISO? How I'm sure that area overxposed is always at same refer level?
It' impossible.

Or not ?


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Re: Zebra Issue on 4K Production Camera

PostTue Apr 15, 2014 8:19 pm

silvio bonomi wrote:Sorry Adam but I not understand...in ( all) other cameras when you apply a gain (or iso level changes...) overexposed area change. How is possible to have a reference limit if the limit is, for example, 90% and if the area of zebra not change, at variations, of ISO? How I'm sure that area overxposed is always at same refer level?
It' impossible.

Or not ?


The BM cameras are not like other cameras. They shoot RAW to cinema DNG. They don't apply analogue gain to change ISO. They are have a native ISO (800 on the BMCC and BMPCC) and apply digital gain or attenuation when shooting to ProRes.

The Zebras are based on the sensor data before any ISO gain/attenuation is applied. So the zebras are always based on 800 ISO (in the BMCC and BMPCC). If the highlights are clipping at the sensor, even if you lower the ISO that data has been clipped.

Also when shooting RAW ISO is only meta data. It's not burnt into the file.
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Re: Zebra Issue on 4K Production Camera

PostTue Apr 15, 2014 10:43 pm

And in addition to that: The zebras indicate rgb-mix clipping, at least they do in the bmcc and bmpcc. This means that if you set zebra to 95% and point the camera at a bright blue light source you might not see zebra even if the blue channel is already clipping, because the overall brightness isn't clipping yet. So better set zebras to 90% or even lower, or at least keep the above in mind when using saturated color lights.
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David Chapman

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Re: Zebra Issue on 4K Production Camera

PostWed Apr 16, 2014 6:28 pm

Have any other 4k owners experienced this zebra issue after updating to 1.6.2?
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Re: Zebra Issue on 4K Production Camera

PostFri Jun 06, 2014 3:46 am

I haven't done extensive testing, however Zebras are not a safe way of avoiding clipping on this camera.
Meter it to get a true stop differential. Recently had Zebras set to 100%, pulled them back half a stop and skin still clipped.
Definitely time for a firmware update to smooth things out on this Camera.

The 2.5k is an incredible camera, The 4K definitely needs tweaking.
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Re: Zebra Issue on 4K Production Camera

PostSat Jun 07, 2014 12:42 am

David Chapman wrote:Is anyone else having issues or problems with zebras set to 100% on the 4k Production Camera? My camera has been working flawlessly until today. Zebras set to 100% now only appear in the upper corners of the image on the LCD, even though the whole image is overexposed. The iris button still steps down the aperture to avoid clipping, but the zebras don't display appropriately.

I do see zebras over the whole screen when below 90%.

This is a shot where the sky above the fence is over exposed, but the screen only shows zebras in the top corner.
Image


Yep, it appears to be sporadic for me. Not sure what triggers it.
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David Chapman

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Re: Zebra Issue on 4K Production Camera

PostSat Jun 07, 2014 2:27 am

I wasn't able to resolve this issue, but Blackmagic support sent me a brand-new camera. They were amazing through the entire process.
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theregal3260

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Re: Zebra Issue on 4K Production Camera

PostSat Jun 07, 2014 6:53 am

my 4k camera not work at 100 % of zebra in film mode work on video mode . in film mode clipping at 95 % of exposition . the camera is brand new
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Re: Zebra Issue on 4K Production Camera

PostSat Jun 07, 2014 1:40 pm

theregal3260,

I would contact tech support.
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Marius Viggen

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Re: Zebra Issue on 4K Production Camera

PostSat Jun 07, 2014 10:08 pm

I used to be a owner of a BMPC. I returned the camera, and get by very well with my BMCC.
My 4K camera had varying performance of the zebra function, changed every week. It was no use at all.
It also had severe FPN, severe clipping, not recognising my sandisk extreme 480gb SSD, and no RAW. The camera has some kind of psychological disorder, maybe borderline or even a psychosis. Anyway,
the BMPC is a fiction, a fantasy, it doesn't exist really. If it ever will come in to being, as a normal
healthy and fully functioning camera, I will buy it. And the zebras, like everything else on this camera, just
forget it.
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Mike Loshchinin

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Re: Zebra Issue on 4K Production Camera

PostSat Jun 07, 2014 10:28 pm

Come on redmaks don't spoil my day man! I've just received my BMPC and it's charging right now near me on the sofa, I haven't even turned it on yet!
And like 5 min ago I tried to download the latest firmware but "Download Now!" button just not working!
Damn these problems scare me. I'll say a little prayer and turn it on :o)
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Marius Viggen

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Re: Zebra Issue on 4K Production Camera

PostSun Jun 08, 2014 9:46 am

Sorry Mike, I didn't meen to scare you. I know how it feels to open the amazing looking box containing the
mythical BMPC 4K, charging the battery for the first time. Its like waiting for the doctor to tell you if your tests
were positive or negative. Its a gamble. But you might be one of the lucky ones. There are people out there telling wonderful and thrilling stories of BMPCs that work, and they say these cameras are able to produce
stunning images. There are also people out there that claim they have tried one of these cameras, and
seen them work with their own eyes. So good luck! Please tell us what happened when you turned it on.
And please tell us there is no FPN!
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David Chapman

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Re: Zebra Issue on 4K Production Camera

PostSun Jun 08, 2014 2:15 pm

Mike,

I wouldn't download and try to install firmware without using the camera first. In fact, I wouldn't install anything unless you are having issues with the camera. Keep it running whatever firmware it came with until they release 1.8.

Also, you can use the camera without charging it. Right out of the box it should have around 50% battery.

Good luck!
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Re: Zebra Issue on 4K Production Camera

PostSun Jun 22, 2014 1:12 am

David Chapman wrote:I wasn't able to resolve this issue, but Blackmagic support sent me a brand-new camera. They were amazing through the entire process.


I'm having a similar problem with my brand new 4k. Did your old camera slowly develop this issue or was it always like this? Does the new camera have any similar issues? I plan on contacting support but I'd like to know what your experiences were.

Thanks.
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Re: Zebra Issue on 4K Production Camera

PostSun Jul 19, 2015 1:42 am

I have this issue as well. At 100% zebras barely show on the corners and don't show at all anywhere else. At 90-95% they show up in the corners but not in the center. At lower percentages they show up increasingly well throughout.

Bummer, as I just had the camera replaced already. Back to support. :?

Morisato, what happened with yours?
Last edited by stevefal on Sun Jul 19, 2015 3:57 pm, edited 1 time in total.
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David Chapman

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Re: Zebra Issue on 4K Production Camera

PostSun Jul 19, 2015 1:13 pm

The solution for me was to get a completely new camera. This was early on so they may have steps to fix this on your current body. I'd definitely call customer service and perhaps point them to this thread for reference.
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Re: Zebra Issue on 4K Production Camera

PostSun Jul 19, 2015 8:32 pm

I also see that the Iris button stops working in some situations. It happens quite often and most often after just using the manual buttons (|<, >|). For example if I use Iris on a scene, and then bump the aperture open using >|, then hitting Iris again does nothing. I can push it any number of times in this state and it will do nothing even though the scene is overexposed.

If I then refocus on another scene, the Iris button may start working again, including when I return to my original scene.

This is very repeatable.
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Re: Zebra Issue on 4K Production Camera

PostThu Jul 23, 2015 4:18 am

I just got the replacement camera from BM. The zebra and iris are non-issues on the new one. However it has vertical banding in the ProRes HQ output. Odd that it's not in the RAW. The banding is plainly visible without lifting shadows. The previous camera with the zebra/iris issues does not have this problem.

Any idea how to get a fully tested camera from BM?
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Re: Zebra Issue on 4K Production Camera

PostFri Oct 02, 2015 2:02 am

I just noticed I never followed up on this. The last camera I mentioned had a verified FPN issue, so it was replaced as well. The fourth and hopefully final camera is so-far-so good. To recap, here is my camera replacement history:

1) Original purchase - used for a while and found dust on sensor under glass. Not serviceable. RMA replace.
2) Replacement 1 - zebras did not show correctly and auto-iris was intermittent. RMA replace.
3) Replacement 2 - strong fixed pattern noise. RMA replace
4) Replacement 3 - Looks good, fingers crossed.

The three replacements were in immediate succession. That is, each issue was there out of the box.

The good news is that it ultimately got resolved, and BM support took good care of me in spite of the initial quality issues.
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Re: Zebra Issue on 4K Production Camera

PostWed May 10, 2017 8:35 pm

Digging up an old thread, I have a fairly new BMPC 4k from Amazon and I've been having issues where Zebras at 100 aren't showing up under any circumstance. I've been trying to figure out how people are saying they're shooting with Zebras at 100 and so long as they don't see the bars, they have plenty of range. I've realized that at 100, I can't see any bars (even if I aim at a light bulb and see a black hole, still no zebras). If I drop down to 95 then they start to appear, and at 90 they're about what I'd expect. Sounds like a return and replacement is probably in order, still within 30 days.
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Re: Zebra Issue on 4K Production Camera

PostThu May 11, 2017 4:33 pm

Andrew, at 100-percent Zebrzs, they (Zebra stipes) show only when sensor starts to clip, so if you see zebras when they are set to 100, your clipping the sensor in those areas. Changing the ISO, does not change when this happens. Also, the blue channel can clip,withoutmthe zfebra pattern showing.

Try setting the camera up outside on a sunny day, with a fast f/1.4 or so lens, wide open, aim at a white card set when direct sun is hitting it (not Not aim the camera directly into the sun) and you should see Zebra pattern on the white card at 100-percent setting. If not, then exchange he the camera. Doing this at night in a house wi a household lightbulb might not be enough to clip the sensor, and display the zebras pattern.
DS
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Re: Zebra Issue on 4K Production Camera

PostThu May 11, 2017 4:58 pm

Denny Smith wrote:Andrew, at 100-percent Zebrzs, they (Zebra stipes) show only when sensor starts to clip, so if you see zebras when they are set to 100, your clipping the sensor in those areas. Changing the ISO, does not change when this happens. Also, the blue channel can clip,withoutmthe zfebra pattern showing.

Try setting the camera up outside on a sunny day, with a fast f/1.4 or so lens, wide open, aim at a white card set when direct sun is hitting it (not Not aim the camera directly into the sun) and you should see Zebra pattern on the white card at 100-percent setting. If not, then exchange he the camera. Doing this at night in a house wi a household lightbulb might not be enough to clip the sensor, and display the zebras pattern.
DS


Hi Denny, yeah, definitely aware that the zebras will only show with sensor clipping. I tested some daylight shots wide open and not even specular highlights from the sun off of chrome will show a zebra. I can shoot raw frames where literally 90% of the pixels are truly beyond clipped and unrecoverable, and not a single zebra stripe will show. They only start to appear at 95%. Seems like a camera issue similar to Steve's where he would only see them in the corners, except in this case they won't show at all. I have a replacement unit coming on Monday, so I'll do a side by side test to see if the new body shows clipping where the current one doesn't.

Thanks!
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Re: Zebra Issue on 4K Production Camera

PostThu May 11, 2017 6:54 pm

Just a quick followup. I noticed that at 95 in RAW mode, I can just barely see a few pixels of Zebras in the corners of frame. If I reframe the clipping element to the center of frame, no zebras at 95 or 100 no matter what. Very similar to the image posted by Corie. Either we're all getting the same RMA'd camera body, or this is an issue that seems to effect more than a couple bmpc 4k's.
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Peter J. DeCrescenzo

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Re: Zebra Issue on 4K Production Camera

PostThu May 11, 2017 7:03 pm

Hi Andrew: It might not make a difference, but just to check: Have you installed the latest BMPC-4K camera firmware (version 4.3.2) released April 12, 2017, available on BMD's support page?
https://www.blackmagicdesign.com/suppor ... al-cameras

Most BMPC-4K cams (including mine) don't have the issue you describe. If it's not due to a firmware installation issue, your camera may unfortunately require hardware repair.

Let us know what you find out.

EDIT 9/15/17: See viewtopic.php?p=363972#p363972

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Re: Zebra Issue on 4K Production Camera

PostThu May 11, 2017 7:36 pm

I was on 4.3.2. Tried rolling back to 4.3.1 just to see if it helped and unfortunately it didn't. Didn't mean to imply that it was a common issue by any means, no doubt that 99%+ of bmpc 4k users don't have this issue. It's just a very odd and specific problem that seems to effect at least a small handful of units. I'll be really interested to test it against the new unit arriving on Monday, should shed some light on it (no pun intended). I'll grab some photos from the screen as well.
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Re: Zebra Issue on 4K Production Camera

PostFri May 12, 2017 2:11 am

Thanks Andrew for the update. Goo d,jack with this, might still be worth it to contact BM about it, the ca era is still being supported.
Cheers
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Re: Zebra Issue on 4K Production Camera

PostThu May 18, 2017 11:53 pm

Just following up on this. The replacement body arrived today and the zebra behavior is completely different under the same circumstances. Basically, the new unit works exactly as expected, zebras show up when set to 100 if the sensor is clipping, and the zebra pattern is also consistent across the screen, it doesn't taper off towards the center of the screen.

I'll try to nab some photos to show the difference over the next day or two before I return the defective unit to Amazon.
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Denny Smith

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Re: Zebra Issue on 4K Production Camera

PostFri May 19, 2017 5:48 am

Good,mglad you got it sorted.
Cheers
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Re: Zebra Issue on 4K Production Camera

PostFri May 19, 2017 3:31 pm

Grabbed some photos using the same lens and settings on each camera back:

- Original camera with Zebras set to 100 - The light should be clipping, there's no detail that will be recoverable. Notice that even the histogram shows what looks like a nice rolloff, don't believe it, I was fooled by this a few times. The data is gone:

https://www.dropbox.com/s/m398dsfjqazag ... 6.JPG?dl=0


- New camera body - Zebras at 100 and showing clipping as expected. Notice that the histogram is also showing clipping. I haven't done any software updates on the new camera yet, but thought it was odd that it lists the mode as 4kp24 and the old body lists 2160p24. They're both set to the same mode, RAW, so maybe it's just a firmware difference?

https://www.dropbox.com/s/69p215abmcl7u ... 3.JPG?dl=0


- Original camera body with Zebras set to 90 - This is where the Zebras finally start to show, but they do so in an odd pattern that tends to breakup or disappear towards the middle of frame:

https://www.dropbox.com/s/d6hjas0wagsn7 ... 7.JPG?dl=0


- New camera body with Zebras set to 90. Zebra pattern is more consistent across frame and the histogram is displaying more accurately.

https://www.dropbox.com/s/75481ucqo3v5t ... 5.JPG?dl=0


Anyways, I think I've pretty much exhausted this one and am ready to get back to shooting, much happier now that the exposure is being metered correctly!
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rick.lang

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Re: Zebra Issue on 4K Production Camera

PostSat May 20, 2017 4:27 am

I also shoot with zebras set at 90% to give me a better warning of impending trouble.


Sent from my iPad using Tapatalk
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Peter J. DeCrescenzo

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Re: Zebra Issue on 4K Production Camera

PostFri Sep 15, 2017 5:43 pm

Apologies if this "fix" has already been posted in this long thread or elsewhere, but yesterday I think I finally saw this odd zebra issue in my BMPC-4K:

If ProRes is set to record in "Video" dynamic range, later when you switch to recording RAW (which is always recorded with "Film" DR), zebras do not display correctly (if at all) while the camera is set to RAW.

Here's the workaround:

To insure zebras are displayed correctly in RAW mode, first set ProRes to record with "Film" DR, then switch to RAW mode.

(This is using the most-current firmware for the BMPC-4K, which is confusingly indicated as "4.3.2" by Blackmagic Camera Setup "4.3.3" app. Not sure if that's a typo or intentional on BMD's part.)

Do others get similar results with their BMPC-4K cameras? What about other models, such as BMCC & BMPCC?

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