Scott_Warren

Here's an old Blackmagic discussion from 2014 regarding flickering with CDNG and a solution (at the time) to fix it:
http://54.172.192.242/viewtopic.php?t=17205&p=108038

Also an Adobe feature request to disable auto-exposure adjustments so that people could use Camera Raw for color grading as another option:
https://adobe-video.uservoice.com/forums/911311-after-effects/suggestions/34158610-provide-option-to-turn-off-image-adaptive-when-i

On 2/11/2020 at 2:20 AM, paulinventome said:

Good you've passed it on.

I hear there is hopefully a firmware release at the end of this month/early next.

I reviewed all the footage I shot and some of it quite low light but didn't see *any* flickering. So i may have just been lucky or it's a combination of settings that brought it on.

For you does it flicker all the time or just at the start?

I see in the data that the black level can go lower than the black level adjustment, meaning that the blacks can be a bit clipped. In Resolve i don't know if it assumes the black level value in the DNG or if it adjusts it accordingly. I'm going to have a closer look because it might be there's a little more data in there sometimes.

cheers
Paul

 

It definitely tends to flicker all the time with the range of ISOs I listed.

I haven't tested this theory, but I wonder if it might be related to the shooting mode issue Andrew found with the incorrect exposure preview in single-shot mode? I don't know WHY it would be related, but it's another thing to test. I have the camera in manual, single-shot mode when not in Cine mode. I'll do a test putting it into continuous mode before capturing some more clips. It would be insane if there's a Goldilocks zone of settings the camera needs to have to avoid flickering   That or it's just a software issue, which it well seems to be. 

On 2/8/2020 at 11:20 AM, paulinventome said:

Okay, so you're right - there's something going on here. Although my 800 is stable and i got a quick flicker in 400, just once at the start of recording. There was a fix to the original firmware that 'stopped' something that sounded like this. But clearly hasn't. Although it's not something i've seen in the footage i've shot - so i can't say it's always happening.

I've gone to the source of the files and i believe there's some scaling to the channels that is the cause, in which case there's hope to fix the data before debayer if it has caused a problem.

In the DNG's there is a value called black level, which is subtracted from the image. I see different minimum values for this across two DNGs and i can compensate for that in RAW Digger to see. Even doing that i believe there is a scale going on with the channels.

If it's something that can be sorted it would be best to sort this before debayer in the RAW DNG files.

I will have a word with them to add to any other reports sent.

What we should work out are the circumstances under which the camera does this...

cheers
Paul

EDIT: So i've passed on the files to sigma and see what they say. Useful for others that have similar files to do the same.

 

Thank you for looking under the hood, Paul! I've been moving the last few days so I haven't been on the forum as much.

I did see talk related to the auto-black level issue with CDNG as a format years ago when it showed up on the older Blackmagic cameras, so it's interesting to see this show up again. 

I've sent Sigma several emails and linked them to other user videos on YouTube where the issue is happening. 

Sigma NY is curious to look at my camera to see if 1.01 didn't correctly overwrite 1.00 somehow. 

I don't mind the growing pains of a new camera system when the image is so good. The joys of technology! 

44 minutes ago, paulinventome said:

It's not something i've noticed so far but will give it a go tomorrow. What frame rate and bit depth? It could be related to that rather than the camera. How about shutter speed?

I thought i could see some pulsing from the lights but you say you see the same in daylight?

And which ISO is causing the biggest issue for you?

cheers
Paul

Thanks for the quick response, Paul! In the vanity shot there is 60hz pulsing from the halogens, but that's stable while the flickering is more spastic, and only on the low end.

Frame rate is at 23.98, shutter at 1/50th (which seems to be the case whether I use 180 degrees or just specify 1/50th according to the DNGs). All 12bit at full 4K res recorded to the T5 1TB. 

Here's the current behavior of my camera:
ISOs 100-320 are OK, 400-2000 flicker, 2500-3200 are OK, 4000 flickers, and then 5000-12800 are OK.

All of the ISOs that flicker do it in the same way, so it would be tough to say that one is worse than the others.

It also doesn't seem to be related to how I'm treating things in Resolve as I'm doing pretty basic stuff to it via the ACEScc pipeline. Flickering is present regardless of what pipeline is used. 

It's quite the mystery!

Hello all, long time reader / lurker and recent Sigma fp buyer here.

I wanted to join into the fp conversation and ask if anyone else is experiencing black level flickering with firmware 1.01 with 12bit 4K capture?

There are a handful of quick technical tests I've done to figure out the flickering behavior, and this is the most comprehensive:

It doesn't show in the above video, but ISO 400 actually still flickers. With my own camera, 320 is the highest I can go on the low end, and the next one up without flickering is 2500. 

On the other hand, it doesn't seem to be a massive loss right now since 320 + F1.4 seems to be enough to capture a dark city road close to how it appears in person, as you can see with this clip:

Would anyone be willing to do a quick ISO test of their own camera to see if you have any flickering blacks at each ISO level? It shows up quickly, so each ISO wouldn't need more than 5 seconds of capture time to see it. It doesn't seem to matter what the light source is, either, as it happens in sunlight as well as with LED lighting. 

It may be subtle in the image if it happens, but you'll definitely see it happen in the bottom of the waveform on playback in your post software of choice. Oddly, it seems to mostly affect the red and blue channels. 

I've tried resetting the camera and re-installing the firmware to no avail.