why does sLog needs so much light?

[Clermond]

I did a short test in my dimly lit cabinet, comparing my "ready to shoot everything" Gamma Cine 4 profile and sLog. I only pushed ISO and kept aperture the same. In Gamma Cine I ended with ISO 4000, in Slog 12.800. From my experience it's dangerous to underexpose as it will produce horrible noise when you push the clip in Resolve. It still looks way better in 2K RAW provided that you expose close to the right. And that made me end in high ISO..

 

[cuervo]

Actually, I've been surprised at the quality of the scenes I've had to shoot in diminished light. Slog2 recorded out to an O7Q as a .DNG does surprisingly well. There is a perception of underexposure, if you look at the monitor and even the WFM. But, in post, with no correction, the images come out exceptionally well. And with a little judicious dabbling, some very nice looking results can happen. As I've developed my workflow, I'm no longer using any recommended LUTS. They all seem to hurt the images. And I've become particularly attached to using the REC709 color space offered by Resolve in the DNG RAW codec settings. It's oversaturated, more like the ubiquitous Kodachrome. And learning to use some Layer Mixer nodes to eliminate that dreaded red/purple pixelation goes a long way to helping.

 

[nyvz]

I did a short test in my dimly lit cabinet, comparing my "ready to shoot everything" Gamma Cine 4 profile and sLog. I only pushed ISO and kept aperture the same. In Gamma Cine I ended with ISO 4000, in Slog 12.800. From my experience it's dangerous to underexpose as it will produce horrible noise when you push the clip in Resolve. It still looks way better in 2K RAW provided that you expose close to the right. And that made me end in high ISO..

Not really surprising if you are comparing directly. In both gammas you were likely using the same analog gain setting (approx. 15-18db gain). Slog2 and cine4 have different grey points and different isos, because they have different purposes and post workflows. The higher iso of slog2 is mostly counteracted by its lower grey point and contrast which give the appearance of lower exposure, so they may appear similarly exposed at the same gain setting. This is why you probably shouldn't monitor in slog2 as its not really designed for a WYSIWYG workflow.

 

[Gene Sung]

It works well in diminished light IMO. I've shot a lot of low light tests and I've been really surprised by how nice S-Log 2 looks, especially when you crush the blacks a bit.

S-Log 2 with internal AVCHD looks really noisy when underexposed, but with the 7Q it's much better.

 

[Colinelves]

I agree with the other guys. I was using the O7Q for the first time in anger yesterday and the results, once taken into resolve were very good - and I was exposing for ISO 2000 at 0db gain (although exposing for ISO 1000 would most probably give a better result). I suspect the issue is the way you're handling it in post.

I'm still working out a good workflow, but my experimentation so has drawn me towards using Resolve, Cinema DNG settings:
- Colour balance: As shot
- Gamma: BMD Cinema
- Colour: BMD cinema
- Highlight recovery: selected

then applying the Sony Slog2 to Rec709 LUT: i.e. the 3D cube provided by sony for the F65/F55. I tried the CD LUTs and they didn't work for me (the Slog2 one was a bit odd and the Rec 709 just looked terrible IMO).

That workflow seemed to produce really nice images, possibly a little dark, but a slight boost in the Camera Raw settings made up for that (exposure 2.0) and honestly, the images were really good: very clean, even considering I was shooting 240fps so the chip was running hot.

 

[Clermond]

thanks guys for all your answers! First of all, I did not compare directly. I was wondering why sLog2 is so dark and then I shot Gamma Cine 4 to see how it is there. I did not judge the image by the monitor but on waveform monitor on 7Q and on the LCD of the FS700.

 

[Finn Yarbrough]

My understanding of the Log compression is that there is more information stored in the lower 50% than the upper. So the footage looks and reads under-exposed, but it's actually not.
In other words, exposing the way you would in rec709, even with charts and a waveform monitor, you would actually be losing some information to the way it's compressed. The rule of thumb seems to be to expose a grey-card at 35%, which will definitely look dark on both your monitor as well as a waveform monitor.

 

[Clermond]

hm.. than it's maybe my workflow which get's me these noisy low light images.

I went through resolve as described above:

I'm still working out a good workflow, but my experimentation so has drawn me towards using Resolve, Cinema DNG settings:
- Colour balance: As shot
- Gamma: BMD Cinema
- Colour: BMD cinema
- Highlight recovery: selected

but if I boost exposure settings to 2.0 or above I get into trouble. I hope I can show some footage after tomorrow's shooting

 

[Colinelves]

hm.. than it's maybe my workflow which get's me these noisy low light images.

I went through resolve as described above:

I'm still working out a good workflow, but my experimentation so has drawn me towards using Resolve, Cinema DNG settings:
- Colour balance: As shot
- Gamma: BMD Cinema
- Colour: BMD cinema
- Highlight recovery: selected

but if I boost exposure settings to 2.0 or above I get into trouble. I hope I can show some footage after tomorrow's shooting

The exposure setting is really sensitive - going above 2.0 definitely started to make things dramatically overexposed to me. However - the key question is: how did you expose in the first place?

I set my exposure using a light meter (metering at ISO 2000) and double checked on the O7Q (basically checking nothing was clipping at either end). The results were good, albeit looking a little under in resolve. If I have time I'll post some shots later on.

 

[paulcurtis]

I think what's confusing is the ISO is an apparent iso based on the grey point of both Slog and Cine4 whereas we are thinking of it as an absolute value that the sensor is set to. So ISO2000 on Slog is the same as ISO400 (or is it 500) on cine4 - in other words after all the log processing grey on the Slog would be identical to grey on the cine4.

I was doing some interior shots and no issues with range clipping. Because the result is linear i exposed skin higher than normal, making sure there's no clipping. I took the files into resolve with it set to clip, as shot, BMD log, BMD log and Highlight recovery then applied the 3D cube from CD direct to the footage (to 709). This pretty much knocked it to what it was when shot. I ended up gamma'ing it down because i think i read somewhere that gamma wasn't quite set right. Either way the results to my eye looked pretty good actually, i found the highlight rolloff on skin to be far superior to pre RAW. Better than the cine4 i shot with previously. There were some aliasing issues on hair but not a big deal. At this stage i'm just generating proxies for the edit.

I believe there's proper support for cDNG coming for Adobe, exactly what that entails i'm not sure. The current support is next to useless. There is a plugin called Ginger HDR but that's just about to be discontinued and also i think it requires and intermediate step. I'm aware of forthcoming support in a few other apps too - direct for cDNG which will be great for me.

Until then, Resolve appears to be the best way forward.

I have some low light/high range stuff coming up this weekend, so that will be a good test too. Because it's so easy to take the exposure down properly with linear footage my gut tells me to light up then take down. Using that extra highlight detail at the top. This should give nice dense and detailed shadows. I feel the shadows are the weakest area on the 700, certainly on the cine curves i've had very patchy results in darkness.

cheers
Paul

 

[Colinelves]

I took the files into resolve with it set to clip, as shot, BMD log, BMD log and Highlight recovery then applied the 3D cube from CD direct to the footage (to 709). This pretty much knocked it to what it was when shot.

Ah-ha! That's why the CD Rec 709 LUT looked so wrong. Thanks for the heads up on that. The Sony LUTs definitely looked better than the CD ones, but there were still problems (they basically looked quite dark and I ended up with a bit of ugly multi-coloured noise coming through when I brought it all back up. But applying the CD LUT and bringing down the gamma (quite a bit actually!) it started to look quite good - without the multi colour noise issue.

I'm quite looking forward to the new firmware as the current set up is a bit fiddly.