FS5: Raw: Atomos vs. Convergent Design vs. Sony

A

Atobit

Active member
I started to play with the Raw file out of the Atomos Shogun (the first generation).
On the FS5 I use the S-Log2/3 for the exposition setting as I was also recording XVAC internally.
The CDNG file out of the Shogun is very much under exposed, I understood that on the Convergent Design 7Q+ that’s the same situation, you have to use a LUT on the recorder to properly expose the CDNG file.
The down side is that you overexpose by a large amount the internal XVAC file.

How about the Sony Raw out of the AXS-R5, is it the same situation?
 
Atobit said:
I understood that on the Convergent Design 7Q+ that’s the same situation, you have to use a LUT on the recorder to properly expose the CDNG file.
The down side is that you overexpose by a large amount the internal XVAC file.
Click to expand...

That is completely false. The same exposure works for the 7Q+ external recording and the internal recording at the same time. In addition, the use of LUTs is totally optional and whether you use a LUT or not should not affect your ability to expose properly. I've never used a Shogun but I'd be quite surprised if it wasn't just as easy to use as the 7Q+.

There are also no issues with exposing for RAW on the R5 and internal at the same time. One exposure works for both.
 
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OK Thanks, I've misinterpreted the information I’ve read about the 7Q+.
I have to check further, I likely have missed setting up properly the Shogun.
 
Back in 2014, I tested one of the Blackmagic studio cameras with 3 external recorders - the original Shogun, one of the Odyssey models (maybe the 7 even), and the HyperDeck Shuttle 2 - and all three of them were crushing my blacks and underexposing the image. The ProRes 422 HQ file looked completely different than what I saw on the camera's screen and the external recorder screens (Shogun and Odyssey). BM engineers didn't have an answer and I wrote it off as a bad unit (a rental).

In late 2015, I rented the camera again (from a different place) and it again produced the same results with the original Shogun.

I never figured it out because I didn't use the camera much, but I'm only telling you this story because since then I've learned not to really trust that all external recorders play nicely with all cameras in all settings.

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If all of your camera and recorder settings are correct - and the Shogun/Sony isn't the problem - the only other possibility I can think of is that Resolve is manipulating your footage upon import for some reason, and you're not seeing the original RAW data.

There are also times when people accidentally bake a LUT into their ProRes footage and the exposure could then of course differ from an internal recording, but that doesn't apply here.
 
Understood, the FS5/Shogun should not be the problem.
I forgot to say that the “Raw to ProRes” file out of the Shogun is properly exposed, but when I switch the output to CDNG, it’s under exposed.
Tonight I’ll look at the Shogun setting and post picture/files I’ve recorded.
 
Here is a frame from the XVAC file:

XVAC_SLog3.jpg


Here is the Raw to ProRes from the Shogun:

ProRes.jpg


Here is the Raw from Shogun:

Raw.jpg


open in Resolve with this setting:

Project_Settings_and_DaVinci_Resolve_by_Blackmagic_Design_-_12_5_4.jpg


Here is a link to download the first Raw frame:

http://atobit.com/download/fs5_shogun_raw/?wpdmdl=1003&masterkey=589b1436826fd


In the Shogun with the firmware 6.6 beta for Raw recording, there is no other option than setting the input and the recording format (ProRes or CDNG):

Shogun_CDNG_Beta1.jpg
 
I don't use Resolve and the last time I poked around it looked different, but a lot of the same concepts apply so I took a look. If you're a pro at Resolve, this won't help you, but:

What are your camera raw codec settings?

Your project settings windows looks different than mine...but I noticed here you can process the footage via Sony RAW or CinemaDNG, which provides different settings/options.

Have you tried adjusting any data levels? Color space? Gamma?

The default ISO looks to be 800? Is that what you're seeing?

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The footage definitely looks underexposed here no matter which setting I change (and again, I don't know this software and using the free version), but if I had to make an educated guess I would say that is how the recorder is capturing the image.

I tweaked some settings to see how the image would respond. I would post your question on BMCuser or Blackmagic's forum and see if anyone can help. There are wizards over there.


Test.jpg
 
I expose to the right with the O7Q+ and view through the Slog2+2(exact names escapes me but it provides for a normal view with +2 stops of exposure) LUT. It looks very washed out in the sony viewfinder. I'm considering buying a viewfinder that I can plug into the SDI output of the Odyssey.
I've never compared my DNG's to the internal recording. But the image quality when working this way is nothing short of outstanding. Signal to noise ratio is incredible. Sharpness and lack of compression artifacts is top notch. You can also brighten the image quite a bit in post if needed before noise becomes a big issue.
My read on the situation is that the camera sensor is actually ISO 800 based on the RAW data passed to the recorder. I think this is how Sony makes an inexpensive camera noisier- by making it faster!
You can set your exposure compensation so that 'push auto' gives a ballpark good exposure.
I'm not saying that this is the easiest workflow, but if image quality is your primary concern, RAW>CDNG overexposed ~ two stops will give the best results from the camera. I understand that CineEI on the FS7 is how you get you expose properly with the same sensor. With the FS5 you need external equipment.
You can also overexpose the internal recording in slog2/3 by two stops and use a compensating LUT in Resolve to crush a lot of noise out of your image, if you don't need all of that extra headroom in the highlights. You would need an external monitor that accepts LUTs to see your image as you intent it.
 
Atobit said:
With Resolve, where I have to increase the exposure in the Raw Setting tab.
Click to expand...

I think there might be some confusion about why the cDNG RAW files looks dark... they looks dark because they don't yet have a video gamma yet applied; it's a LINEAR image.

A linear image exposed based on the Sony recommendations for middle grey in slog2 has the grey point way, way low if recorded as a linear file, as each stop is a doubling of code value. Here's an animation I did years ago that might help, even though it's for the older Gemini recorder, the concepts are the same...

https://www.youtube.com/watch?v=aQJHqDGRoa8

And here's a more practical guide to getting these linear RAW files to work in Resolve and match up with what you see when monitoring or recording in slog2...

https://www.youtube.com/watch?v=1RAGvJa0wgw

Regards,

Jim Arthurs
 
I think we know the RAW should be processed, but it still looks underexposed. Are you saying there is a difference in monitoring vs. recording with the Sony RAW? Like what you see is NOT what you get?

Maybe take a look at the DNG/frame in Resolve if you're interested and/or have time, and let us know what you think...
 
I use a 7Q+ with my FS5 and it works perfectly, but I also have a shogun for my A7S2 and I once tried it out to see how the FS RAW on the Shogun was since the Shogun has the ability to burn in LUTs and that could be useful sometimes, and I couldn't get it to give me a proper slog2 image that worked with any normal slog2 luts. I also haven't heard of anyone successfully using the Shogun with the FS5/FS700... Clearly something is getting recorded, but it seems to be different than what comes out of a 7Q and it's unclear what the best workflow is for it. It seems it will take some work since neither the RAWtoProres and RAWtoDNG seem to fit into existing slog2 workflows which seems pretty frustrating.

It's not surprising to me that DNGs look totally different than everything else, that is often the case with the 7Q as well (though I don't shoot RAW often). DNG is highly dependent on workflow since to be viewed it the application processing the footage will determine what it looks like since there is no gamma baked in and a lot of the look depends heavily on the software being able to read and understand and properly use the included metadata. In my experience even on the 7Q, getting DNGs to go back into a normal slog2 workflow takes a very careful and specific workflow.

I don't think Resolve is showing Linear, just a different gamma curve that probably has completely differently balanced middle grey or exposure metadata isn't coming through. That looks dark but it doesn't look like linear light...
 
NorBro said:
I think we know the RAW should be processed, but it still looks underexposed. Are you saying there is a difference in monitoring vs. recording with the Sony RAW? Like what you see is NOT what you get?

Maybe take a look at the DNG/frame in Resolve if you're interested and/or have time, and let us know what you think...
Click to expand...

Watch the videos I linked, they explain both the theory and the practical steps to get things to match up. They explain why they look under-exposed, and how to address in in Resolve. Think about it... the top 50% of all code values describe just the brightest white stop the sensor captures before clipping. HALF! 50% of what's left describes the next stop below the highest stop, and so on down and down, until full stops of picture information are being described with tiny handfuls of code values in the shadows, even in 10bit or higher.

Usually you're not used to seeing linear images "out in the wild" without a gamma correction of some sort, but that's the case with the cDNG's. So you see it and say, wow, that's under-exposed. The slog2 image you see is a re-distribution of those stops so they are of more or less equal code values per stop. And while that slog2 image is no more a final display image than the RAW linear one is, you're more used to seeing the flat low contrast slog2 due to so many cameras using it (or other log variants) that you've got a mental baseline of what it looks like.

Now, of course I'm not saying there aren't valid reasons to over expose compared to the Sony recommended levels, for reasons of noise control, etc. But a properly exposed to Sony recommendations image when monitored in slog2 WILL look under-exposed as a RAW cDNG. Apply the correct LUTs to the RAW image and you can match back to what you were monitoring as slog2.

Here's more info, back from the original FS700 & RAW roll-out by Art Adams and Adam Wilt... start watching at about 38min, 30 seconds...

https://vimeo.com/69884277

Regards,

Jim Arthurs
 
I'll take a look - thank you - but it just sounds like LUTs 101. You expose a scene based on a LUT you're using to monitor the image and it will look good, but the footage may later look underexposed or overexposed in your software, but when you apply the LUT you used, it normalizes everything and looks like what you saw on the screen when filming.

I guess I wasn't there and don't know what the OP saw, but the DNG still looked super dark.

With Blackmagic cameras, the exposure wouldn't be so drastically different when shooting RAW if I was previewing the image on the camera's screen using the "FILM" setting, and it would look the same in Resolve "as shot". I guess I just got caught up with curiosity a bit. (I've never shot Sony RAW CinemaDNG.)
 
Thank you Jim for those very informative feedback and video link about the Sony FS’s raw.
Thanks Doug, NorBro, nyvz and SamEd for your feedback.
At first I thought I was doing something wrong or the equipment has an issue. I know understand the principle of the Raw CDNG delivered by Atomos and Convergent Design recorders.
Yesterday, in Resolve I’ve applied on the Atomos raw file the Convergent Design suggested LUT and it effectively convert the CDNG raw to a S-Log2 image.
During the week-end I’ll post images with waveform and RGB parade.

Saying that, as opposite to Convergent Design, Atomos did not publish any information about how to manage the raw that they deliver. I have check if the Shogun onboard LUTs has similar exposition compensation characteristics than the CD ones.

I’m too considering getting a viewfiender as the FS5 one is not really good.
 
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