Exposing Raw on the FS700 with the O7Q

C

Colinelves

Well-known member
How are people exposing 2K/4K at the moment? so far I've done one project at 4K (Sony recorder) exposing for ISO 2000 - and the result was extremely noisy.


Since getting my O7Q I've done a couple of shoots at 2K Raw. The first I exposed for ISO 1000 and it still seemed quite noisy. The second time I exposed at ISO 640 (as Cine 4 seemed to be a good flavour in 8bit land) and the results were very good. Nice clean blacks, but still maintaining a decent roll off in the highlights - and holding the clouds (albeit on a very grey day!)


Post wise I imported into Resolve, set camera raw to CinemaDNG, Gamma & colour BMD film, high light recovery and colour balance as shot (I used preset daylight for both shoots at the second was all exteriors and the first I light with my LED panels set to daylight) and set the input LUT to the Convergent Design Slog2 to Rec 709


I then did a quick one-light: pulling down the gamma by 0.15 (to correct this apparent gamma problem) and exported to QuickTime (2K DCI frame).


Exposing this way I got really good skin tones and since It needed no exposure correction was applied in the Raw I suspect the CD LUT assumes a base ISO of 640, or there abouts.


BTW: by 'exposing at ISO 640' I mean I pulled out my light meter, set it to ISO 640 and the shutter speed and set the stop based on the meter reading. I know some people advocate ETTR - but that's a bit of a ball ache for long form work.


At some point I'll check where skintones fall when exposing at 640 - so I can setup the zebras correctly for docco work (once it is possible to set the zebras below 70%).


How's everyone else working it?
 
Wasn't sure, but did you say you are setting the camera to S-Log2 and then using your light meter set at 640 to expose or are you setting the PP to Cine4? I also find the picture very noisy, so far I've been overexposing and then bringing it back in post, overexposing seems to blast the noise out, but I'm not sure if this is a good strategy. I'd like to try your method and see if it works.
 
Well, setting your light meter for 640 (while shooting "ISO 2000" on the camera) is essentially ETTR, right? Except you're doing it in a more precise way. You're overexposing by a predetermined amount that is repeatable from shot to shot, location to location. I think that sounds like a pretty good idea.
 
ilnow said:
Wasn't sure, but did you say you are setting the camera to S-Log2 and then using your light meter set at 640 to expose or are you setting the PP to Cine4? I also find the picture very noisy, so far I've been overexposing and then bringing it back in post, overexposing seems to blast the noise out, but I'm not sure if this is a good strategy. I'd like to try your method and see if it works.
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yes, slog2. Cine4 was just my 'inspiration'
 
jshbckr said:
Well, setting your light meter for 640 (while shooting "ISO 2000" on the camera) is essentially ETTR, right? Except you're doing it in a more precise way. You're overexposing by a predetermined amount that is repeatable from shot to shot, location to location. I think that sounds like a pretty good idea.
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exactly. Consistency makes for a happy grade.
 
Have been doing the sames tests today and I reckon exposing for ISO 640 is the way to go too. I find using both a light meter and the false colour function works best. More testing to do before I can be confident of this but it looks like exposing to the left is a no go with Slog2 on the FS700, even with 2K RAW
 
Sorry in advance if this is a stupid question... I understand that we need to overexpose slightly (blacks at 20 on the WFM) but what does ISO 2000 really mean? How do you actually light for ISO 2000?

Is it a bad idea to use the DB Gain on the camera? Can you get the same result by not using the Gain (and avoiding the noise) and just boosting gamma or exposure in Resolve?
 
http://www.builtbyugene.com/mov_tests/7q/7QTests_140122_0101Bracket.mov.zip

Here's a series of bracket tests I did, all at ISO 2000. 2K RAW then compressed to 4:2:2 Pro-Res LT (LT for faster download). I even left the Histogram on for you guys. Please download and grade it as it should grade well.

To my eye, most of the stuff that is a bit under-exposed looks fine

1) On the first series of my living room with the sliding glass door. The first shot is the most exposed (in the middle) and it actually looks noisier than the following shot that is one stop under. Also, first shot that is most exposed, all the detail outside my back sliding glass window is gone (and not recoverable in the grade). The 2nd shot that is a bit underexposed, the detail is still there. So for that shot, I much prefer the shot that is 1 stop under, for both noise and highlight detail.

On all outside shots, I've had the best results with the histogram in the middle, not to the right.

2) the first shot of the M&Ms jar, the overall exposure is about 2 stops under and it looks fine to me. It does start getting a bit noisy on the red box on the following two shots, but those are pretty far under.

To me, the noise is no worse than AVCHD. I suppose if you left it in S-Log 2 or were judging the noise based solely on un-graded S-Log 2, then there's noise. But the moment you crush the blacks even a little, much of the noise goes away. But maybe I'm just a bit more noise tolerant than most people.

To me, I've had good results even in lowlight when the histogram is a couple stops under.
 
really interesting Gene, thanks for sharing! I am very curious for your shots as my experience with exposing to the right was better. I am still learning a lot from day to day and you have way more experience than I have. Download is very slow it seems some other people are curious too ;-)
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edit.
Download finished and I am pretty impressed! What was your setting in Resolve?
 
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Having been slightly bitten by undercooking exposure a little in a very dark set of scenes i'd suggest Colin's approach as being pretty sound. In other words not using the monitor for exposing right now and doing it properly. For me i was lighting up in real life, to expose down on camera so blacks were really black (cutting ambience down) yet still exposing up a bit more to bring down again in post for noise. I had practicals in shot so mindful of balancing the clipping. What bit me was the elevated blacks on the monitor and the nature of the scene needed to be mostly dark, no mid greys. This obscured the WFM a bit. Both the WFM and the LUT blacks were also raised. So basically there was no way on the monitor at this point to actually monitor the scene with any degree of sense, switching to the LUT just gave a bright scene and a false sense of exposure. Yes the RAW data was pretty much exposed where i ultimately wanted it, not a stop or so up so i could bring down in post. Plus at ISO2000 meant noise not so bad.

Obviously new firmware with blacks being black would help and some LUTS (hopefully) to make the viewing more relaxing for the director. I do think that whether the WFM should show the underlying RAW signal or the signal through the LUT should be a user option. I can see in some very subtle scenes wanting to WFM monitor through a LUT (as happens right now)

Having said that i'm happy with the feeling of the footage, i just lost my safety margin and will chalk that one up to experience.

Of course i need to double check my post workflow. It's quite easy to get it wrong. On the PC the blacks in the DNG appear elevated too, meaning that interpreting it as BMD log and then applying a LUT might not yield true results. I can't say this for sure, on a Mac the blacks appear, blacker if that makes sense. It's really quite tough to find an easy way to unfold these DNGs into a full range file to work with outside of resolve. At the moment the best approach appears to be to generate Log files from Resolve.

I'll see if i can grab a few stills later on to illustrate.

cheers
Paul
 
Clermond said:
edit.
Download finished and I am pretty impressed! What was your setting in Resolve?
Click to expand...

Hey Clermond,

I didn't do anything special. Just used the stock settings suggested by Convergent and applied the S-Log 2 3D LUT before exporting as Pro-Res. But yeah, I've done a lot of bracket tests at this point for outdoors, daylight I tend to prefer to keep it in the middle. For low light stuff, shots that have been a stop or two under have been fine, at least for me. Just adjust the levels a bit.
 
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