SLOG ISO ratings?

[Bruce Schultz]

S-Log held that white at just under 70%, the LUT was displaying it right about 100%, but that was where I set the LUT at for HG40 + EV.

[Dennis Hingsberg]

ok bruce, thanks.

[Leonard Levy]

Bruce why and how do you use the LUT.
I haven't used SLog much but I found I like it better to just set the monitor to higher contrast & sat. That way my monitors waveform is accurate & I can yank it back to preset and see what I'm really carrying in the highlights. I figure if it can look good in the monitor I'm plenty safe as long as I set my levels correctly. That's assuming a pretty loose working environment though. For clients it mighty bounce around though. Do you turn up the monitor saturation when you use the LUT?

[Bruce Schultz]

I found on this shoot last week that the LUT was not looking even as good as the uncorrected S-Log feed so in the end I turned it off because I'd done a good enough job with the producer so that he was comfortable knowing that the desaturated but perfectly exposed S-Log would be an easy grade for him.

I'm pretty much at the point that I'm going to either have to do live grading on set using the S-Log feed, Live Grade, HDLink, and a MBPro - or start making custom LOOKs for the F3 which might be able to address the desaturation and exposure issues with camera LUT generation. Leaning towards the first, however, CVP File Editor is now available on Mac so making 3D LOOKs for camera might be a good starting point.

[Leonard Levy]

CVP file editor doesn't allow you raise saturation, so it doesn't really make a true viewing LUT to my mind. Also since the existing LUT's throw away the added headroom you are gaining in sLog then if you are running that feed through a waveform you're getting inaccurate waveform info. If I could make a really good LUT that also held my headroom , that would be great, but without it I'm sticking with the tweaking the monitor for now.

[Mark Kenfield]

Just to clarify things a little further, if I rate the camera at 800 ISO (at 0dB in SLOG) on a lightmeter, that will give me Middle Grey at 38%?

[Dennis Hingsberg]

Apparently ISO doubles in SLOG mode to 1600 from 800 but.........

I would strongly suggest you take a quick moment to light your grey card, fill your frame with it, then turn on your spot meter function and display the % IRE reading in camera, and adjust your lens iris until you get 38%

Now you can take a light meter at the grey card and dial up or down your ISO value until your f-stops match between the light meter and lens.

If you want to see a video by Abelcine where Andy Shipsides performs a similar test, here is a link: AbelCine Tests the Sony F3 ISO Rating | CineTechnica

[Douglas Villalba]

Sony rates S-Log 0 db at EI 800.
In my exposure test changing actual f-stops, shows 800 to be the middle between over and under exposure of the full S-Log DR.
I don't believe that you could determine actual usefulness of under or over exposure with a chart set at a given exposure without actually over and under exposing.
My 2¢

Sony PMW F3 S-Log Usable F-Stops Test on Vimeo

[Dennis Hingsberg]

I have used SLOG with the camera rated at 800 ISO, but "The Film and Digital Times" article however indicates on page 4 that "The ballpark sensitivity rating is ISO 800 (1600 in S-log), with an exposure range greater than 13 stop".

The best thing to do is shoot your own grey card and use spot meter function in the F3 to rate it yourself.

Rating your camera's ISO lower (say at 800 instead of 1600) will cause you to over expose by one stop, so you might place skin at 1 stop under middle grey using a camera rating of 800 but in reality you're placing skin right at middle grey.

[Mark Kenfield]

Thanks Dennis, Douglas.

Dennis, having to wrangle the camera around to spot meter a grey card up close is what I'm hoping to be able to avoid (if I can). It definitely works for getting perfect exposure, I'm just wondering if I can make my life easier by picking up something like a Sekonic L758Cine (which is rather easier to wrangle).

Douglas, thanks for the video. Rated at ISO 800, the camera certainly still appears to have enough overexposure latitude in SLOG to turn in good results. Though with those lampshades in the background only a stop away from clipping at ISO800, I'm starting to think that rating the camera at ISO 1600 is probably the way to go (for the extra stop of overexposure latitude it provides), graded up it certainly still seems to hold all of the shadows and mid-tones well.

Cheers,

Mark

[Alister Chapman]

The confusion over the ISO rating comes from the way the F3's ISO doubles when you switch from progressive to interlace.
In interlace the base ISO is 800, in progressive 400. In S-Log mode that becomes 1600 in interlace and 800 in progressive.

[Dennis Hingsberg]

Mark sorry if I wasn't clear, once you do your own verification of your ISO using your own grey card, light meter, camera and lenses, you won't need to use the grey card on your shoots or between shots, just use your light meter but the point is you did your own tests and calibration of equipment.

I say never trust any elses settings or observations and always do it yourself first, and in advance of your shoot. I just read a thread where a guy downloaded someones light meter profile for various cameras and went ahead and did a shoot without conducting any prior tests or validation. His footage was under exposed and he didn't know why. 1.) He used a profile for the wrong RED camera 2.) He ended up using the VF to judge exposure instead of "trusting" the light meter 3.) he did not test it.

Camera firmware updates can influence sensor sensitivity. Meters can be calibrated in 1/3 increments to give different readings, plus offer many modes of operation - often all of this resulting more often than not in the incorrect use of light meters - and then people hate them or say how useless they are. Everytime I shoot I use a light meter, I get the exact amount of light I need all day long as setups and camera angles change, and that consistency shows in my work.

More about how I use lightmeters and the F3 can found in my blog hingsberg's blog | Director & Cinematographer

[Dennis Hingsberg]

Originally Posted by Alister Chapman

The confusion over the ISO rating comes from the way the F3's ISO doubles when you switch from progressive to interlace.
In interlace the base ISO is 800, in progressive 400. In S-Log mode that becomes 1600 in interlace and 800 in progressive.

Like I said always do your own calibration of light meter to your camera and setup. Myself and some others have rated the F3 in progressive mode 1/48, 0db mode at 800 ISO, not 400.

Regardless, the main thing when using a light meter is to know when you are hitting that middle grey with a specific volume of light.

[Douglas Villalba]

I would say that the camera has a wide latitude that in most cases it really doesn't matter as long as you are within 400 and 1600 EI for your flesh tones. It is only when you go into the extreme ends of f-stops 6.5 under and over exposure.
For example: Assuming that you have a person exposed correctly under sunlight. Your background is a dark brown wall with an EV of 6.5 f-stops over the person, you will still get a nice image no matter if you rate it at 800 or 1600. If instead the wall was white even with the amount of light you may want to under expose the person in order to get details on the white (EI 1600).
It is mostly a problem when you have a third object that the EV is 6.5 f-stops under the person. If this object is white no problem, but if it is dark you will provable get no details.
There are not too many situations were you have 13 f-stops spread. If you do and you understand how the sensor reacts, you can play with it to get a decent image. You may need to decide if you can live with blown highlights or detail less shadows.
It really doesn't matter mush if you rate it at 400, 800, 1200 or 1600. At the mid point it will look good. At the extremes it could make the difference.

[Chris Medico]

And remember that mid in LOG isn't 50%, its 38%. ;)