Sigma Fp review and interview / Cinema DNG RAW

[Lars Steenhoff]

Interesting results, by the way I think you mean ISO 25600 and ISO 12800 instead of 256,000 and 128,000 right?

[rawshooter]

25 minutes ago, Lars Steenhoff said:

Interesting results, by the way I think you mean ISO 25600 and ISO 12800 instead of 256,000 and 128,000 right?

Yes, sorry, too late in the evening. (And I can't edit my original posting anymore.)

[paulinventome]

@rawshooter Excellent work, thank you.

I don't know very much about BRAW and workflows. One thing i am aware of is that quite a few cameras (usually not doing RAW) will do their own highlight processing in camera before spitting out an image. It's nigh impossible to get an R3D processed via IPP2 without it in because it's also a valid method of reconstructing an image (just as filling in missing pixel values). So the check would be are those BRAW files actually just raw data from the camera or do they have any camera processing in them?

Then an important part of range is the colour quality and so it's quite usual for people to shoot colourful scenes or charts and over and over expose them, bring them back to a standard exposure and see how the colours are - in day to day shooting this can be important. To do this i personally tend to use shutter speed, not aperture as lenses aren't that accurate (not sure shutter speed is either but think it's more likely)

I do have a step wedge here somewhere that i would like to shoot some range charts but have mislaid it! I reckon the fp is doing around 12 stops and it's fairly clean in the shadows so it's quite a usable range. As i said before there is a sensor mode that does 14 bit out but don't think that's being used anywhere. One thing with the fp is that it's easy to compare stills to cine.

cheers
Paul

 

[paulinventome]

On 1/6/2020 at 12:55 AM, CaptainHook said:

"BMD Film" (version 1 which will be applied to non-BMD DNGs) will just apply a log type gamma curve and not touch colour (gamut). So you will be getting Sigma fp sensor RGB space in terms of gamut and no colour 'errors' except that a sensor response isn't meaningful on a display. To transform into a common display space would not be straight forward though unless Sigma or someone provided the correct conversion, so unless you could get something you're happy with by manually correcting the colours it might be easier and more straight forward to decode into a known defined space like 709 or something and go from there.

Thanks for Clarifying officially!

If you actually do this then the settings are Color Space: Blackmagic Design, Gamma: Blackmagic Design Film. The gamma curve brings all the range in and the colourspace is BMD.

What does that actually mean though, you say that it won't touch gamut?

To try and understand i use the CIE diagram scope. And setting the DNG to P3 vs BMD Film 1 (in a P3 timeline) i see the first two diagrams. First is BMD Film into a P3 Timeline and the second is debayering P3 into a P3 timeline.

Now this is basically a point of confusion in Resolve for me - to understand what resolve is actually doing in this case. A saturated Red in sensor space in the DNG is transformed into 709/P3/BMD Film - but is that saturated Red actually mapped into the target space or is it placed at the right point. I cannot work it out. So for example if that sensor Red is outside of 709 space then IMHO Resolve could either clip the values or remap them. But if you switched to P3 and that Red lay within it then no mapping has to happen.

But on the CIE diagram i do not see this. I would expect to switch between 709 and P3 and the colours inside the triangles not move. In other words in a sufficiently large colourspace on that CIE diagram i ought to be able to see what the camera space is (ish).

So when i do this and choose BMD Film and set the timeline to that as well i get the 3rd diagram - which is beyond visible colours

so i have to assume i just don't understand what Resolve is doing here or that CIE diagram is not working?

Any light shed (pun intended) would be super nice!

cheers
Paul

 

[rawshooter]

3 hours ago, paulinventome said:

So the check would be are those BRAW files actually just raw data from the camera or do they have any camera processing in them?

BRAW is quite processed (debayered in-camera, with noise filtering and sharpening applied), so it's debatable to which degree it can still be called a raw format. This is how BM officially describes it:

"The new advanced de-mosaic algorithm is a central component of Blackmagic RAW. Part of the RAW processing is moved out of software and into the camera, where it can be accelerated. Noise management, sensor profiling and new edge reconstruction algorithms are used to produce high quality cinematic images with incredible depth, crisp details and beautiful image separation."
https://www.blackmagicdesign.com/products/blackmagicraw

But it's the only raw-style video format that the BM Pocket 4K can record with current firmware, respectively in the currently-sold hardware generation of the camera. It can record DNG only as stills.

[paulinventome]

15 minutes ago, rawshooter said:

"The new advanced de-mosaic algorithm is a central component of Blackmagic RAW. Part of the RAW processing is moved out of software and into the camera, where it can be accelerated. Noise management, sensor profiling and new edge reconstruction algorithms are used to produce high quality cinematic images with incredible depth, crisp details and beautiful image separation."

That's my thinking. AFAIK highlight reconstruction happens best in XYZ space and i'd read that the BRAW files are white balanced. But that was something i'd read and have no idea whether it's true or not. It's difficult to know whether this is RAW or not - the ability to debayer according to new future algorithms and no white balance baked in really seems RAW to me. I don't quite understand the benefit of raw processing in camera vs a log file out of a camera...

cheers
Paul

[cpc]

As promised, the Sigma fp centered release of slimRAW is now out, so make sure to update. SlimRAW now works around Resolve's lack of affection for 8-bit compressed CinemaDNG, and slimRAW compressed Sigma fp CinemaDNG will work in Premiere even though the uncompressed originals don't.

There is also another peculiar use: even though Sigma fp raw stills are compressed, you can still (losslessly) shrink them significantly through slimRAW. It discards the huge embedded previews and re-compresses the raw data, shaving off around 30% of the original size. (Of course, don't do this if you want the embedded previews.)

[Lars Steenhoff]

Thanks for the slim raw update, @cpc 

[rawshooter]

14 hours ago, cpc said:

As promised, the Sigma fp centered release of slimRAW is now out, so make sure to update.

Does it also work under Linux with Wine?

[cpc]

17 minutes ago, rawshooter said:

Does it also work under Linux with Wine?

No idea, but I won't be surprised if it does. I don't recall any arcane Windows trickery that would hinder Wine.

[Lars Steenhoff]

 

[Andrew Reid]

I am very interested in the new L mount Sigma lenses, that's the newly designed 24-70mm F2.8 in the Japanese video. Will definitely try and pick up one of those when it's available in the UK!

[rawshooter]

In practice, you can switch forth and back between full frame 4K raw and APS-C 4K raw video recording without great image quality penalty. (The difference in noise and resolution is IMHO invisible if you master in 1080p). And you can put the full frame vs. APS-C crop switch on the camera's quick access menu.

That effectively turns any prime lens into a dual-focal length lens - or virtual dual lens turret. Often, this makes a zoom lens unnecessary in the field.

It's a neat (and often overlooked) little feature of the camera.

[Lars Steenhoff]

yes I used it to film the moon yesterday, really nice quality the crop, and the fact that every prime lens become two focal lengths as you mentioned. 

I'm planning to get an old contax zeiss 28-70 f3.5-4.5 to get by with a small zoom lens, and also take a prime lens like the 45.

The sigma 24-70 2.8 is also good looking of you need autofocus and do also stills

[Andrew Reid]

Try the old Canon 28-70mm F2.8 EF, it's parfocal and can be had for as little as £250

Best kept secret of the EF lenses this one is.

[CaptainHook]

On 1/7/2020 at 9:35 PM, paulinventome said:

What does that actually mean though, you say that it won't touch gamut?

To try and understand i use the CIE diagram scope. And setting the DNG to P3 vs BMD Film 1 (in a P3 timeline) i see the first two diagrams. First is BMD Film into a P3 Timeline and the second is debayering P3 into a P3 timeline.

So when i do this and choose BMD Film and set the timeline to that as well i get the 3rd diagram - which is beyond visible colours

BMDFim Gen 1 doesn't touch gamut, so for DNG's what you get is the sensors native response to colour, which is not suitable for a typical display. You can't really map a sensors spectral response to just 3 chromaticity points like a typical gamut and show it on a CIE plot either, but people do it anyway to give a rough idea. But most sensors will definitely have a response beyond visible colours so this is expected.

 I don't work in the Resolve team but CIE scope in Resolve will be plotting our Blackmagic Cinema Camera spectral response as best it can because it assumes if you're using that colour space you're using our camera. It doesn't try work out a gamut for whatever camera clip you're currently viewing. So the chromaticity points for the gamut you see are based on the original  Blackmagic Cinema/Pocket Camera.

When you transform from one space to another, you are scaling values by a 3x3 matrix. There's no algorithm deciding if a pixel value is within a gamut to leave it a lone depending on the target gamut. It just scales it by the 3x3 matrix regardless. Resolve does have a RFX plugin though that will allow you to selectively decide how to deal with out of gamut colours when transforming from a larger space to a smaller, it's under "Gamut Mapping" in the Colour Space Transform plugin. But this isn't typical 'standard colour science', because generally you want your transforms to be "reversible" and when you start doing non-linear manipulations it gets very difficult to reverse.

On 1/7/2020 at 11:15 PM, paulinventome said:

That's my thinking. AFAIK highlight reconstruction happens best in XYZ space and i'd read that the BRAW files are white balanced. But that was something i'd read and have no idea whether it's true or not.

It's best to white balance and do highlight recovery in native camera/sensor RGB space. Blackmagic RAW is not white balanced, its the native sensor response and we white balance it during decode. XYZ is okay to white balance in as an alternative if you can't do it in sensor space and this is possible because you can transform to XYZ from any gamut, but if you've already white balanced you can't do common highlight recovery (in XYZ or otherwise) that uses unclipped channels as during white balance you clip the highlights to ensure white = white.

[Thomas Hill]

4 hours ago, Andrew Reid said:

I am very interested in the new L mount Sigma lenses, that's the newly designed 24-70mm F2.8 in the Japanese video. Will definitely try and pick up one of those when it's available in the UK!

The FP could really use the OS that Sigma put in the Canon, Nikon and, even, the SA versions of the 24-70. 

[Emanuel]

1 hour ago, CaptainHook said:

It's best to white balance and do highlight recovery in native camera/sensor RGB space. Blackmagic RAW is not white balanced, its the native sensor response and we white balance it during decode. XYZ is okay to white balance in as an alternative if you can't do it in sensor space and this is possible because you can transform to XYZ from any gamut, but if you've already white balanced you can't do common highlight recovery (in XYZ or otherwise) that uses unclipped channels as during white balance you clip the highlights to ensure white = white.

Fair explanation. Not recommendable to white balance when we shoot braw, you say, is that so?

[Lars Steenhoff]

8 hours ago, Andrew Reid said:

Try the old Canon 28-70mm F2.8 EF, it's parfocal and can be had for as little as £250

Best kept secret of the EF lenses this one is.

Yes its a nice lens the Canon but also 880 gram vs the 320 gram of the zeiss.

And zeiss is also parfocal.

I'm trying to make a travel kit, very lightweight for filming.

https://www.zeiss.com/content/dam/consumer-products/downloads/historical-products/photography/contax-yashica/en/datasheet-zeiss-vario-sonnar-35452870-en.pdf

[Andrew Reid]

Ah didn't realise it was parfocal as well. Not bad for £200.  I might try and fine the Zeiss but none on UK eBay at the moment, mostly seem to be in Japan.

This is where I get my old lenses from when I'm in Berlin:

https://www.shphoto.de/catalogsearch/result/?cat=0&q=anamorphot

Highly recommended

I'll see if they have any in.