Sigma Fp review and interview / Cinema DNG RAW

[paulinventome]

1 hour ago, Scott_Warren said:

Looks like we're a part of a lucky few, Noli  What's weird to me is that the flicker seems to affect the red and blue channels more than green. 

Wouldn't that indicate something happening with white balance? It makes no difference having a WB preset selected like Sunlight, or manually dialing in 5500K instead. Tried it with disabling all of the auto lens corrections, with autofocus, manual focus etc. I feel like I've tried most variables that would affect it. 

Did you post a couple of DNGs before? I think you did?

What would be interesting is that in the DNG there is a value called Brightness Value which i noticed changes with ISO. If this is being changed in the DNG by mistake then it may explain the data. Have you still got the same DNGs handy?

cheers
Paul

[Scott_Warren]

1 hour ago, paulinventome said:

Did you post a couple of DNGs before? I think you did?

What would be interesting is that in the DNG there is a value called Brightness Value which i noticed changes with ISO. If this is being changed in the DNG by mistake then it may explain the data. Have you still got the same DNGs handy?

cheers
Paul

I don't have those original ones from pages back, but I can post some frames from 320 (which doesn't flicker) and some from a flickering ISO if that would be useful!
Edit: Uploading a 1 second DNG sequence from both 320 and 800 to google drive. It'll be ready in a moment. 

[Scott_Warren]

Here you go Paul (or anyone who's curious):

https://drive.google.com/open?id=1tgJ7nNLGzTOXLvVRJkn06yr8PGBgRNcF

Folder for ISO 320 with 24 frames, and a folder for ISO 800 with 24 frames. The flicker at 800 is pretty crazy so hopefully that's a treasure of information for you to dive into. 

[paulinventome]

19 hours ago, Scott_Warren said:

Folder for ISO 320 with 24 frames, and a folder for ISO 800 with 24 frames. The flicker at 800 is pretty crazy so hopefully that's a treasure of information for you to dive into. 

Initially it reminded me of using canon lenses many years ago where the electronic aperture was not 100% accurate from frame to frame. But then further investigation shows that this just appears to be in the shadows. (Although it could just that it is more observable in the shadows). The two screens show the shadow data changing quite obviously. There are two 'modes' that it appears to be flicking between

It doesn't appear to be an overall exposure change.

So is this identical in 8 bit, 10 bit and 12 bit? Because one finger could point at the encoding. If it's the same on all of those i would have to suggest the body itself or it's something that we're all getting but not noticed (and i would notice this!)

The fact that it doesn't do it in all the ISOs is unusual as well.

Are you able to swap the body? Or borrow one to check?

cheers
Paul

 

[Scott_Warren]

23 minutes ago, paulinventome said:

Initially it reminded me of using canon lenses many years ago where the electronic aperture was not 100% accurate from frame to frame. But then further investigation shows that this just appears to be in the shadows. (Although it could just that it is more observable in the shadows). The two screens show the shadow data changing quite obviously. There are two 'modes' that it appears to be flicking between

It doesn't appear to be an overall exposure change.

So is this identical in 8 bit, 10 bit and 12 bit? Because one finger could point at the encoding. If it's the same on all of those i would have to suggest the body itself or it's something that we're all getting but not noticed (and i would notice this!)

The fact that it doesn't do it in all the ISOs is unusual as well.

Are you able to swap the body? Or borrow one to check?

cheers
Paul

 

Heya Paul,

I'm not able to swap the body for another one (I'm the only person I know with an fp in my circle of photography friends) but I could certainly try to see if this happens at 10bit and 8bit, as I've as yet only used 12bit for capture. 

[paulinventome]

1 hour ago, Scott_Warren said:

Heya Paul,

I'm not able to swap the body for another one (I'm the only person I know with an fp in my circle of photography friends) but I could certainly try to see if this happens at 10bit and 8bit, as I've as yet only used 12bit for capture. 

Ah, well yes, do that. Because i find it difficult to believe that the physical sensor or hardware is changing depending on ISO like that and the way the data is looking it seems like a bug perhaps between sensor and writing out the RAW data. 8bit and 10bit would be slightly different.

I've mostly *not* used 12 bit because i am in 25p land. I have used it when shooting without sound sync but certainly beyond tests and messing around i've not 100% focused on it...

cheers
Paul

[Scott_Warren]

1 hour ago, paulinventome said:

Ah, well yes, do that. Because i find it difficult to believe that the physical sensor or hardware is changing depending on ISO like that and the way the data is looking it seems like a bug perhaps between sensor and writing out the RAW data. 8bit and 10bit would be slightly different.

I've mostly *not* used 12 bit because i am in 25p land. I have used it when shooting without sound sync but certainly beyond tests and messing around i've not 100% focused on it...

cheers
Paul

Drumroll....

 

10bit has the same behavior as 12bit  Though it seems like 400 is actually now stable with 1.02. No flickering with 12bit or 10bit after checking yesterday's stuff as well.

100-400 = fine
500-2000 = flicker
2500 = fine
3200-4000 = flicker
5000-6400 = fine

Secondary observations:
The over-exposed first frame issue happens only on 125-320. Stable for all others. Possibly related to ISO scaling down from "native" sensor values somewhere? It's interesting that ISO 100 & 400+ is stable and behaves as expected.

For now, I'll just treat the camera like a 400/2500 dual gain kind of deal until I can send it to Sigma for diagnosis. 

 

[redepicguy]

5 hours ago, Scott_Warren said:

I'm getting similar. Although in my tests are as follows:

100-400 are fine. 

500, 640 Flicker

800 Fine

1000-4000 Flicker

5000+ fine. 

And you're right..the whole first frame brighter only happens on ISO's 125-320. So weird. So for me, I'll shoot at 100, 400, 800 and 5k and up. 
 

 

 

[Scott_Warren]

1 hour ago, redepicguy said:

 

That's crazy! I'd love to know how widespread this actually is. Most people will use it as normal (likely with .mov capture) and roll with it without doing pixel peeping so they might not see it, but surely it's not just a handful of cases.

[imagesfromobjects]

Hello- first post here, I hope everyone is doing well in these crazy times. I joined because this is the most in-depth discussion of the fp happening anywhere on the web. And... like most everyone, I have quickly developed a love/hate relationship with its quirks and potential. 

 

I'll skip to it: I just updated it to 1.02 firmware and the flickering blacks are absolutely still there in MOV. I realize (of course) that I'm not going to get the full potential of the camera without an SSD, or at least shooting 8 bit DNG internally, but adding accessories or spending time in post kinda defeats the purpose of the fp for my use case 90% of the time. As such, I'm tinkering with every different possible combination of in-camera settings to get the quality of footage that my 6 year old a7S can get, with little luck so far. 

 

The short version is that there's no way to raise the black levels (and no LOG profile, but you already know that) so the only thing you can do is use the profile with the highest apparent base black gamma level (Portrait, in my testing) and reduce contrast and boost the low end tone curve. It's wonderful that these options exist, but with a fixed black level point, what happens is that the darkest regions between black and shadow just become this murky blob and the DR is strained, so it just looks like crap. It's most evident in shooting low light footage. Incidentally - or not - this is also when the flickering happens. 

 

The settings I've been using are: dumb adapter, manual lenses, manual everything, 180 shutter, MOV ALL1, 24fps (or whatever) and testing every different combination of resolution, as well as reducing contrast and sharpening and trying every combination of color profiles and tone curves. 

 

Ugh. 

 

The good news is that it's an AMAZING stills camera, especially with compact rangefinder lenses. The bad news is that the on-board video is buggy as heck. 

 

If Sigma could fix this, and get rid of the white focus box that's always there in stills mode, it could be perfect. 

 

Thanks for the great thread! 

 

-Tim 

[Chris Whitten]

This has to be something happening to specific cameras and not across the board.

I have have shot several mini-films using 10bit 4K DNG, both at ISO200 and ISO640 and have seen no flickering and absolutely guarantee my first frames are identical to every other.

When others posted their 'flickering' examples I often struggled to see it, but it's definitely not obvious to me in Resolve 16 and I definitely haven't had the issue with first frames.

[paulinventome]

1 hour ago, Chris Whitten said:

When others posted their 'flickering' examples I often struggled to see it, but it's definitely not obvious to me in Resolve 16 and I definitely haven't had the issue with first frames.

On a static scene it's clear. if you download Scotts DNGs it is very obvious, if you go into DNG and bump up the exposure it is even more so. You can see on the scopes that there are two modes that the images are flicking between - one with truncated blacks and one with more shadow detail.

In the DNG there is a concept of a black level. This is subtracted from the data and i thought perhaps that was being incorrectly calculated.

Because it's jumping between two seemingly fixed states - it does seem like a software thing but then we'd all be seeing it.

If it's hardware then is it environment? Temp? 

I need to try a few things, because it looks like it's shadows only but then this is linear data so changes in shadows are going to be much more obvious than lights. 

Scott - do you have a macbeth chart? It would be interesting to have a scene with dark, mid and highlight greys and just shoot that with the lowest iso that flickers, Then we can look at the averaged data (to get around noise) and see if the values are linearly incorrect in the data.

Also i don't see a reply from redepicguy....? Was it removed?

cheers
Paul

[BTM_Pix]

7 minutes ago, paulinventome said:

 

Also i don't see a reply from redepicguy....? Was it removed?

It hasn't been removed.

His reply was to this portion of the post above his from Scott.

15 hours ago, Scott_Warren said:

<snip>

10bit has the same behavior as 12bit  Though it seems like 400 is actually now stable with 1.02. No flickering with 12bit or 10bit after checking yesterday's stuff as well.

100-400 = fine
500-2000 = flicker
2500 = fine
3200-4000 = flicker
5000-6400 = fine
 

<snip>
 

But he has put his own post inside the quoted portion.

So his response was actually :

---------------

I'm getting similar. Although in my tests are as follows:

100-400 are fine. 

500, 640 Flicker

800 Fine

1000-4000 Flicker

5000+ fine. 

And you're right..the whole first frame brighter only happens on ISO's 125-320. So weird. So for me, I'll shoot at 100, 400, 800 and 5k and up. 

------------------

Scott has then responded but as he has quoted RedEpic's post its shows up a blank because its embedded in a previous reply.

Clear as mud !

But that's how it has happened

[paulinventome]

1 hour ago, BTM_Pix said:

Scott has then responded but as he has quoted RedEpic's post its shows up a blank because its embedded in a previous reply.

Whoa, brain is confused! But yeah, i see. I think maybe i'll do some more tests.

On another note one of those GGS VF arrived. It's a nice compact well made however it's not actually big enough to cover the fp screen, you would cut the sides off. So i have no idea what all those that are using it are doing - they would have to stick the magnetic adhesion so it cuts into the screen. Also there is obviously no optical adjustment and actually for my eye i find it clearer about half a CM away from the screen and actually then it does show the whole screen.

So i am wondering if i can make something that means i can have it the right distance from the screen and slots into the small rig cage i have on the camera. 

Does this mean i can get a 3D printer?!

I think the optical quality of sigma is better - this one distorts the sides of the image but it's plenty usable if i can find a way to mount it.

cheers
Paul

[Chris Whitten]

How do I check for flickering in my own footage - what is the methodology?

Forgot to mention, I'm also on 25fps.

I bought and am using the Sigma LVF.

The diopter moves as you walk along, which is annoying. It takes away some of the grip points on the camera, so it is harder to hold.

On the upside, it helps me focus, compose and check exposure. It is very light, but it more than doubles the bulk of the camera.

[Noli]

I just shoot something dark and turn up the shadows in resolve. It's pretty obvious. Just did a quick test with 320 ISO 8bit 25fps and it flickers. Strange that the flickering ISO values seem to be different for everyone

[Scott_Warren]

24 minutes ago, Chris Whitten said:

How do I check for flickering in my own footage - what is the methodology?

Forgot to mention, I'm also on 25fps.

I bought and am using the Sigma LVF.

The diopter moves as you walk along, which is annoying. It takes away some of the grip points on the camera, so it is harder to hold.

On the upside, it helps me focus, compose and check exposure. It is very light, but it more than doubles the bulk of the camera.

Heya Chris,

Here's what I do. Capture at 4K in either 12bit/ 10bit. For every ISO starting at 100, I capture 10 seconds of a static shot. Seems like a long enough time where you'll see it happen if it's going to.

Then fire it up in Resolve and add each clip to a new timeline and look for the waveform behavior seen here:
https://drive.google.com/file/d/1kMpU9QFj92Ly-h7aOkN5Asb9ombpMolX/view

You might not see it in the footage, but the waveform always tells the truth

Paul, I do have a colorchecker! Are you saying to lock off a shot of the chart exposed at speed?

[paulinventome]

42 minutes ago, Scott_Warren said:

Paul, I do have a colorchecker! Are you saying to lock off a shot of the chart exposed at speed?

I was interested whether the exposure changes across the whole image. When it's in Resolve and debayered then there is a gamma curve so it makes it more difficult to see if at source it is an overall data shift. If there were some chips that could be averaged in a frame and then compared to an average in the next frame it might be possible to tell if the values are shifting uniformly.

You see, in the shadow a shift of 6 units in the red (which is what was happening) would be impossible to tell in the upper regions because a sensor is linear. So it's a doubling of value for every stop. But 6 units in the very bottom equates to around 3 stop difference.

Stop 0to1 - has 1 value
Stop 1to2 - has 2 values
Stop 2to3 - has 3 values

so in the first 6 integer values there are 3 stops of light recorded.
At the last stop there are 2048 values allocated. So a difference of 6 units isn't going to show.

Make sense?

I may try to record some as well.

cheers
Paul

ALSO: Another thought, is it shutter speed that is wavering? That is electronic - is there a pattern there, in other words it's not the ISO but the shutter speed at fault? That might explain why different people see it at different ISO values?

[Chris Whitten]

I have a colorchecker passport. I'll try, but I'm a musician, not a film maker.

[BTM_Pix]

2 hours ago, paulinventome said:

So i am wondering if i can make something that means i can have it the right distance from the screen and slots into the small rig cage i have on the camera. 

Does this mean i can get a 3D printer?!

I think the optical quality of sigma is better - this one distorts the sides of the image but it's plenty usable if i can find a way to mount it.

cheers
Paul

Sigma providing the 3D files makes it a lot easier to add your own parts.

This is what your 0.5cm riser would look like and obviously you can then choose what to do with the top of it to make it marry to your preferred method of mounting.