Sigma Fp review and interview / Cinema DNG RAW

[Noli]

So I've done some ISO flicker testing and got some strange results to share.

100-250 / 500-2.000 / 5.000-10.000 / 16.000-25.600 all with no flicker.

320-400 / 2.500-4.000 / 12.800 show flicker.

Overall quite okay compared to what @Scott_Warren tested a few pages ago. So is the flicker issue different for each camera??

I have tried finding the flickering DNG files and opening them in Camera Raw. Previously I got the impression the flicker was not present there, but during this test it showed up there aswell.

At ISO 12800 black levels and colour changed for one, sometimes more frames.

Theres also seems to be a bug where the first frame of a DNG sequence is overexposed. This occured in clips with and without flicker. In the 12800 sequence the first frame is the same exposure as the flicker that shows up later. In the 320 clip the first frame is a little brighter than the next 3 frames, then colour and brightness change for the whole clip and after 7 seconds flickering appears with colour and brightness of frame 2-4.

 

Another interesting thing I noticed is that the noise going from ISO 10.000 to 12.800 and up changes a lot.

Images pushed by 5 stops in Camera Raw.

ISO 10.000

ISO 12.800

[Chris Whitten]

I will check the first frame of my DNGs. I don't remember seeing anything odd, but I tend to shoot longer clips and start my edit a few seconds in to avoid camera shake (as I touch the red record button etc). I haven't seen any flickering, even though most of my footage is low light. I'm in PAL land, so my footage is 25fps shot at 50s.

Sometimes I struggle to see it in examples of flickering footage online though, so who knows....

[Chris Whitten]

Just test shot and I'm not getting any blown out first frames. All my frames look identical.

Everything on the FP and lens set to manual.

Here are 'still' exports from Resolve 16.2. The first frame of my footage. Shot at ISO200, 4K UHD 10 bit, using the Takumar 50mm, no filters.

The first still is ungraded, just set clip to Blackmagic Film. Second still is the same frame (1) just adjusting the lift and gain a bit, adding some contrast and saturation.

[Chris Whitten]

The second stills are again first frame. Shot in a shadier area at ISO400. Same as before UHD 10bit, Takumar 50mm lens.

First still is untouched other than setting clip to Blackmagic Film, second still is light grade by hand - adjust lift and gain, more contrast, more saturation.

[paulinventome]

10 hours ago, Noli said:

Theres also seems to be a bug where the first frame of a DNG sequence is overexposed. This occured in clips with and without flicker. In the 12800 sequence the first frame is the same exposure as the flicker that shows up later. In the 320 clip the first frame is a little brighter than the next 3 frames, then colour and brightness change for the whole clip and after 7 seconds flickering appears with colour and brightness of frame 2-4.

 

Are you sure you are on the latest firmware? This was a bug in the first release but was fixed quite a while ago?

cheers
Paul

[paulinventome]

On 3/10/2020 at 8:30 PM, Scott_Warren said:

Heya Lars, is there a particular way that's best to make a report to Sigma? I've just been using their email address. Though I don't often get a reply back. 

I've always emailed and always had a polite thoughtful reply back, even if it's thanks but we can't talk about xyz.

I would urge as many users as possible to email with their needs - that way they can prioritise them. AFAIK v2 won't have other frame frames and resolutions and i'm disappointed with that. I don't see how much work it would be to add a tone curve to 10 bit for example when they have it for 8 bit. That would sort out quality issues. But if more people email in then they know that really is something we want...

cheers
Paul

[paulinventome]

10 hours ago, Noli said:

Another interesting thing I noticed is that the noise going from ISO 10.000 to 12.800 and up changes a lot.

 

The sensor internally might be dual ISO and maybe Sigma run it in different modes depending on ISO.

I have just done a bunch of tests seeing whether i can match exposure and workflow to be able to cut the footage into Red footage and actually got it pretty close - close enough that i know it will intercut. One observation is that the ISO to match is 2.5x - so if the Red is at 1000ISO then the Sigma needs to be at 2500ISO to match exposure. 

I also notice that in the RAW files Sigma is changing the default brightness level for different ISOs, so that different systems may use that default (like where 18% should be) in different ways. This is something i am still looking at. The example being that if you shoot in ISO400 and look then the shadows are raised and banded but ISO 1600 has the *same* overall exposure level but the shadows are richer. So in each DNG file Sigma is adding a different exposure level to compensate. You may expect the ISO1600 to look brighter overall but that isn't happening if the RAW viewer is using that value - what it is doing is pinning 18% in a different place and giving more under stops than over stops.

cheers
Paul

[Noli]

2 hours ago, paulinventome said:

Are you sure you are on the latest firmware? This was a bug in the first release but was fixed quite a while ago?

cheers
Paul

Yes, I am on the latest firmware. The notes only mention that they fixed the first frames being enlarged.

I have 3D printed a cheap viewfinder attachment that works with a 3.2" Display Loupe you can find on ebay for 20€. I don't know how long it will last but right now it sits pretty tight. It locks into the small vent holes at the top and you can still use all the buttons.

If anyone is interested, message me and I can send you the blender file.

 

 

[Chris Whitten]

My first frames are all normal.

https://youtu.be/pcLDgO0CRCQ

[Scott_Warren]

I've seen quite a few initial frames that are exposed about a stop hotter than what I've dialed in for a video, and this is on 1.01. 

On a call with Sigma support the tech wondered if the firmware didn't properly update from the factory somehow, since I received my camera with 1.01 pre-installed. After numerous re-installs and resets, the behaviors with exposure and flickering haven't changed. If 1.02 doesn't fix these issues, I'll send the body to Sigma NY to let them diagnose what's wrong and nuke the software if need be

You know what would be handy? A sensor whitepaper written by Sigma. Just a blast of all the tech details about the sensor they're using so that we don't have to be quite so investigative. Surely that wouldn't be a big deal for the engineering team to put together. 

[Chris Whitten]

Are you using the body with a Sigma lens, or in some kind of auto exposure mode?

All my frames are exactly the same exposure, but I don't have an L series lens, so I'm using old manual like Leica M or Takumar.

I have found those annoying bugs in the stills function of the camera, but so far the cine mode has been bug free for me.

[Scott_Warren]

Just now, Chris Whitten said:

Are you using the body with a Sigma lens, or in some kind of auto exposure mode?

All my frames are exactly the same exposure, but I don't have an L series lens, so I'm using old manual like Leica M or Takumar.

I have found those annoying bugs in the stills function of the camera, but so far the cine mode has been bug free for me.

Both Sigma lenses: 35mm Art and the 45mm DG DN  Fully manual mode for cine. 

Definitely one of the strangest cameras I've yet owned, haha. 

[Chris Whitten]

Maybe it's something about the electronic communication of the lenses and FP body - even though you are in manual mode?

I have not had this bug with my adapted lenses.

 

[Noli]

2 hours ago, Chris Whitten said:

Maybe it's something about the electronic communication of the lenses and FP body - even though you are in manual mode?

I have not had this bug with my adapted lenses.

 

I am only using adapted lenses with no electronics as well so I don't think that causes the problem.

[Roogii]

What's the chances of 14bit raw video, is the sensor capable?  stills in 14b have substantially better noise/ dynamic range deep into the dark bits of the sensor over using 12b.

What about full sensor 6k 3:2 video, hardware capable? The 4k downsample currently looks decent but DC mode 4k 1:1 pixel sampling does beat it for absolute resolution and aliasing free imaging. 

1080p in camera is quite bad.

More crop modes using 1:1 sensor pixels would be nice such as super16mm also, or simply being able to enter any custom pixel dimensions/ aspect ratio.

Coming from magic lantern I miss zebras and histograms based on raw data.

The FP base iso is 200 not 100.

[paulinventome]

13 hours ago, Roogii said:

What's the chances of 14bit raw video, is the sensor capable?  stills in 14b have substantially better noise/ dynamic range deep into the dark bits of the sensor over using 12b.

What about full sensor 6k 3:2 video, hardware capable? The 4k downsample currently looks decent but DC mode 4k 1:1 pixel sampling does beat it for absolute resolution and aliasing free imaging. 

1080p in camera is quite bad.

More crop modes using 1:1 sensor pixels would be nice such as super16mm also, or simply being able to enter any custom pixel dimensions/ aspect ratio.

Coming from magic lantern I miss zebras and histograms based on raw data.

The FP base iso is 200 not 100.

No chance on 14 bit video at all at the kind of resolutions/rates we're talking about. There's no prosumer/stills sensor that will do this at the hardware level, they're all 12 bit movie mode as far as i can see.I don't see a huge difference between stills and 12bit cDNG though. If the sensor is the Sony one then there is one read out mode, a crop mode that does do 14 bit but as i said, i really don't see that much between 14bit stills and 12bit.

The sensor is being read out at 6k, but whether the camera has enough juice to dump that out to USB i don't know. That is a possibility. More crop modes would be awesome, that's true.

And yes, some kind of visualisation of RAW data would be very useful. 

I don't know what the base iso is though, where did you get 200?

cheers
Paul

[paulinventome]

On 3/12/2020 at 11:06 AM, Noli said:

I have 3D printed a cheap viewfinder attachment that works with a 3.2" Display Loupe you can find on ebay for 20€. I don't know how long it will last but right now it sits pretty tight. It locks into the small vent holes at the top and you can still use all the buttons.

 

That's really cool!

IMHO one of the biggest annoyances is the VF. I'd pay good money for an EVF but there are no small ones - portkeys and zacuto are the smallest but they are still too unwieldy.

There is a collapsable VF from GGS Foto but having a very tough time getting any decent info about it.

I wonder whether a VF with different optics to get it closer to the screen is possible...

cheers
Paul

[BTM_Pix]

44 minutes ago, paulinventome said:

There is a collapsable VF from GGS Foto but having a very tough time getting any decent info about it.

Is it this one ?

http://www.ggsfoto.com/en/products/OCULAR.html

Looks very smart with the Hasselblad 500CM styling !

I bought a (very) cheapo rubber collapsible loupe which was 3.2 inch and works well on the FP but I need to sort out a mount for it.

Based on that, the Nikon D5 version of the Ocular would be the one to get as its the same screen size and the frame looks to be equal thickness on each edge.

This is a UK dealer/distributor for it 

https://www.cameraclean.co.uk/products.php?cat=Ocular+Folding+Viewfinder+-+Black

I've bought quite a few bits off them at the Photo/Video show at the NEC over the years and they were set to be there for this year's one until the cancellation which would have been an ideal time to have a hands on look at the Ocular.

The stuff they pick up distribution for has always been decent quality though so, for me personally, that would maybe less of a risk of the unknown as a blind purchase if they are selling them. 

 

[Noli]

The GSS Viewfinder seems to be very nice. This guy uses it in his video: https://youtu.be/phFyPS_uX4w?t=662

I thought about printing a smaller viewfinder frame in combination with a regular magnifing glas to get something more compact. It's really convenient that Sigma releasd the 3D Models for the FP and all acessories. Since I can 3D print for free at my University I think I will try some more stuff, currently working on a handgrip between the size of the small and large one from Sigma.

 

[Roogii]

Great thankyou Paul. 

What pixel dimension is that 14b crop mode if you know?

I will attach two still raw corner crops,  one 12b the other 14b. Was at iso 100, a dynamic range stress test where i exposed the sensor to max highlight clipping point outside the window. As you can see, deep in the darkest noise of the sensor, 14bit keeps the noise finer and cleaner and smoother with more detail. 

In regards to base iso, i simply started at iso 100, exposed a scene to the sensors highlight clipping point, ramped up the iso whilst keeping exposure at that sensor clipping point. Then chose the cleanest image. ISO 100 and 200 are actually exactly identical for the sensor. If you take an image using iso 100, keep your shutter speed and aperture the same and repeat the image at iso 200 - then take those raw images into a program that displays raw histograms such as raw digger, you will see that 100/200 are the same. The camera will lie to you though, making you expose an extra stop for iso100. Not sure I read anywhere that iso100 is a trick/extended iso, but it appears to be.