UM46 - another case for "hot pixels"

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Emilian Dechev

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UM46 - another case for "hot pixels"

PostSat Apr 15, 2017 10:25 am

Ursa Mini 4.6K - another case for "hot pixels".

Here is a JPEG from a RAW file zoomed at 100% - that means, it is pretty visible.

This is only 1/4 of the whole frame, and we can see 3 dead pixels - 2 green, and 1 red. Throughout the whole frame, there are about 10 more dead pixels.

In the first picture, the exposure was heavily boosted in post, to exaggerate the problem.

I am also attaching a frame without boosting the exposure - the dead pixels are still slightly visible.
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Untitled-1.jpg
Untitled-1.jpg (785.34 KiB) Viewed 1312 times
Untitled-2.jpg
Untitled-2.jpg (564.67 KiB) Viewed 1312 times
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Timothy Cook

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Re: UM46 - another case for "hot pixels"

PostSat Apr 15, 2017 6:32 pm

Hot pixels can happen, I'm sure BMD will take care of this.

The amazing thing about your image is how clean it is!!! It's already super underexposed but then you boost it five stops and not even the slightest hint of FPN! Not a single vertical line what so ever.

I think the 4.6 sensor is a lot cleaner than people think. This looks like it's handling that underexposed image better than a Sony Cinema sensor.

You mind sharing a DNG?
Vimeo.com/dropbars
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Emilian Dechev

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Re: UM46 - another case for "hot pixels"

PostSun Apr 16, 2017 12:30 pm

Hi, unfortunately I deleted the DNGs from this test, but I will make new ones.

Yes maybe my sensor is kind of cleaner, but the vertical lines are still visible in dark areas, especially when doing pans or generally moving. Even in a well lit and well exposed scene, one could always expect to have dark areas, such as shadows or even the actor's hair - there I can see some vertical lines.

About the hot pixels, how BMD could resolve this issue? Is this case suitable for a RMA? I doubt they will trouble to replace the whole camera over several hot pixels.
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Emilian Dechev

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Re: UM46 - another case for "hot pixels"

PostSun Apr 16, 2017 5:24 pm

Here are some DNGs.

Due to the free nature, of "myairbridge", the link will be working only for 2-3 days.

https://mab.to/JC00DsfBE
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Csaba Nagy

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Re: UM46 - another case for "hot pixels"

PostSun Apr 16, 2017 7:11 pm

Over the years I've spent on the forum, Hot / Dead Pixels have been the most widespread issue across all cameras. I'm surprised they haven't found a better end user solution. ( via firmware or even in post through resolve.. I would have thought black shading would solve this, guess it hasn't? )

As for an RMA, I highly doubt they give you a new sensor, the camera is probably run through a better supervised calibration process and sent back.
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Timothy Cook

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Re: UM46 - another case for "hot pixels"

PostSun Apr 16, 2017 8:00 pm

Csaba Nagy wrote:Over the years I've spent on the forum, Hot / Dead Pixels have been the most widespread issue across all cameras. I'm surprised they haven't found a better end user solution. ( via firmware or even in post through resolve.. I would have thought black shading would solve this, guess it hasn't? )

As for an RMA, I highly doubt they give you a new sensor, the camera is probably run through a better supervised calibration process and sent back.



The best sensors in the world have the same issues. The other companies manage all these issues while taking creative control away from the end user. Same goes for cameras that have built in noise reduction that you can't turn off, or skin smoothing that isn't adjustable.
All these other manufactures deal with the same issues but use software to control it at the expense of the creators control of his or her own work.

Just for reference. Sony's way of dealing with hot/stuck pixels
http://www.sonyalpharumors.com/specific ... x-request/
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Csaba Nagy

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Re: UM46 - another case for "hot pixels"

PostSun Apr 16, 2017 9:02 pm

Timothy Cook wrote:
The best sensors in the world have the same issues. The other companies manage all these issues while taking creative control away from the end user. Same goes for cameras that have built in noise reduction that you can't turn off, or skin smoothing that isn't adjustable.
All these other manufactures deal with the same issues but use software to control it at the expense of the creators control of his or her own work.

Just for reference. Sony's way of dealing with hot/stuck pixels
http://www.sonyalpharumors.com/specific ... x-request/


Yes these artifacts inherent to the manufacturing of sensors. They happen. I've spent the last few months working low level with another camera's bayer data, I see it alot. I performed a process similar to the Sony median filter method to cut out hot pixels.

The notion of RAW is pretty misunderstood I think, Lots of processing needs to happen to that RAW before it gets wrapped into DNG ( black shading, hot pixel mapping, flat field correction, etc.. among other things )

Provided a clean "Dark Frame" to locate these pixels, I'd imagine Hot pixel removal would work wonders in resolve if not possible in firmware.

It just makes one think, its got to be a hassle on BMD's end to have to constantly deal with these issues. Especially given its not 100% a hardware defect in most cases, but rather "hit or miss" calibration during the manufacturing stage. ( also just something that develops overtime with sensors )

I suppose they are still doing their part and RMA'ing the cameras and fixing them so it seems to be at least in their eyes, the most effective solution.
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Yuri Gagarin

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Re: UM46 - another case for "hot pixels"

PostSun Apr 16, 2017 9:29 pm

Emilian Dechev wrote:Here are some DNGs.

Due to the free nature, of "myairbridge", the link will be working only for 2-3 days.

https://mab.to/JC00DsfBE

Hi. I can find the one and only dim white pixel in the right upper part of the screen.
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Jamie LeJeune

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Re: UM46 - another case for "hot pixels"

PostMon Apr 17, 2017 9:36 pm

My Ursa Mini 4.6K just went in to RMA for 3 hot pixels (and also non-functioning LANC).
JamieLeJeune_UrsaMini_StuckPixels.jpg
JamieLeJeune_UrsaMini_StuckPixels.jpg (520.57 KiB) Viewed 1007 times


The camera produces lovely images when it actually works properly, but this is the third return/RMA I've had to deal with. A number of producers/directors in my area refuse to rent it for their shoots because they've heard about all the problems. I have to nod my head and agree because I can't honestly tell them otherwise.
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Emilian Dechev

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Re: UM46 - another case for "hot pixels"

PostTue Apr 18, 2017 6:52 pm

Yuri Gagarin wrote:
Emilian Dechev wrote:Here are some DNGs.

Due to the free nature, of "myairbridge", the link will be working only for 2-3 days.

https://mab.to/JC00DsfBE

Hi. I can find the one and only dim white pixel in the right upper part of the screen.



Yes, these files are different from the ones I uploaded initially.

But why would I get 3 hot pixels in the first test, and only 1 hot pixel in the second?

Isn't a dead pixel really dead in all occasions? Or maybe it depends on some variables like sensor running time / temperature, exposure, etc

So we should just accept this as inherent to all digital sensors, as grain is inherent to film, and just live with it. I have yet to meet a client, who will decline a job, over some dead pixels, but still... :?
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John Brawley

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Re: UM46 - another case for "hot pixels"

PostThu Apr 20, 2017 3:38 am

Emilian Dechev wrote:
But why would I get 3 hot pixels in the first test, and only 1 hot pixel in the second?

Isn't a dead pixel really dead in all occasions? Or maybe it depends on some variables like sensor running time / temperature, exposure, etc


It can depend on few things.

First of all, dead pixels increase OVER TIME. So you might get a camera with apparently very few dead or stuck pixels and none that show up, and later you develop more dead pixels that show up in your footage.

Even brand new sensors have many dead pixels from the factory, before they get installed in your camera.

Every camera has a way of re-mapping or turning off these dead pixels. Usually this works without you even noticing.

Dead pixels are more likely to show up when the sensor is hot or has been on for a while. Again, this goes for any camera.

Most people don't realise on their DSLR that the overheating that can happen, isn't about the camera literally overheating or being damaged, but more that the noise (like FPN) or dead pixels can no longer be controlled in an acceptable way. So the camera suggests or forces you to rest the sensor for a bit. The noise floor rises, and other sensor artefacts show up more readily. I think you'll find somewhere in these threads where some have tested the noise floor on BM cameras in normal operating conditions and in super cooled conditions. It's no surprise that the sensor isn't has noisy when the camera is better refrigerated.

Some companies even do after market cooling mods for special purpose use to stock cameras like astro photography, where a dead pixel could eaily become a new star ;-) https://petapixel.com/2016/10/11/cooled ... ar-photos/

So, dead pixels are always there, you just mostly never see them or notice them. If you are, it COULD be a sign that there's an issue with cooling on your camera, or perhaps in some rare circumstances, the dead pixels can't be corrected or turned off. I'd suggest cooling might be the issue in your case if they're intermittently showing up.

You should try BMD service and see what they have to say.

I remember Sony used to say that they wouldn't accept a return under warranty for some of their broadcast cameras unless there was more than 6 dead pixels visible.

If you're lifting them 3 or 5 stops to see them and not always seeing them, I don't think you'll get much sympathy.

JB
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Emilian Dechev

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Re: UM46 - another case for "hot pixels"

PostThu Apr 20, 2017 5:25 am

Thanks for the helpful info John!
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Uli Plank

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Re: UM46 - another case for "hot pixels"

PostSat Apr 22, 2017 6:45 am

Unfortunately hot pixels are normal with CMOS technology. If you check the warranty conditions carefully, even the big players expect you to tolerate a certain number of them.
It would be great if Resolve would offer a simple method of mapping them out with a dark frame from your camera.
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Jamie LeJeune

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Re: UM46 - another case for "hot pixels"

PostSat Apr 29, 2017 6:02 pm

The RMA was successful. My 4.6K Ursa Mini came back with no hot pixels. Thank you BMD Support :D
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John Brawley

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Re: UM46 - another case for "hot pixels"

PostSat Apr 29, 2017 6:13 pm

Jamie LeJeune wrote:The RMA was successful. My 4.6K Ursa Mini came back with no hot pixels. Thank you BMD Support :D


Great to hear !

JB
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Robert Niessner

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Re: UM46 - another case for "hot pixels"

PostSat Apr 29, 2017 7:27 pm

Uli Plank wrote:
It would be great if Resolve would offer a simple method of mapping them out with a dark frame from your camera.


Resolve 14 to the rescue :)
Robert Niessner
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Uli Plank

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Re: UM46 - another case for "hot pixels"

PostMon May 01, 2017 10:56 am

Where? Is there a simple way of applying a dark frame now?

I know there's a dead pixel fixer, but that's manual…

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