F55: Getting the most accurate exposure.

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davegoulding

Member
I am enjoying my new F55 and trying to figure out the best way to get the most accurate exposure when filming in SGamut3.cine while baking in the LC-709typeA look profile? Any thoughts would be appreciated.
 
If you are baking in the LUT to your recording then it's really pretty much WYSIWYG. You can use your "eye" or waveform monitor to see what levels are doing and you will be ok.

If you are NOT baking in the LUT but using a LUT for exposure you need to be VERY careful because different LUTs can have different mapped values for 18% middle grey and 90% white reflectance. So my recommendation if not baking in the LUT but using it for monitoring on-set is to always turn the LUT off and observe your underlying S-Log levels before turning the LUT back on and recording. At least until you get use to what is actually happening with the LUT'd values. Also test the mapped values yourself by using both a grey card and a white card - not only one of the other.

For example with LC709TypeA, 71% IRE is the correct exposure level for a white card not 90% IRE. So if you used 90% assuming you should expose like you would for REC709 you'd be 19% over-exposed which is around 2 stops. LC709Type also maps 18% middle grey at 40%...
 
Before reading all Denis' guide, i tried a number of options for exposing and the most convenient for me ended up being using rec709 and exposing by waveform/eye on the monitor and double checking waveform with slog3 gamma in extreme cases, works 100% for me. If there are no exposure extremes, just expose by 709, there is plenty of range up, if there are some realllly bright areas, check with slog3.

What i noticed with lc709 type a , I and other operators tend to overexpose with it, thus not using this method or you have to be very careful.
 
davegoulding said:
I am enjoying my new F55 and trying to figure out the best way to get the most accurate exposure when filming in SGamut3.cine while baking in the LC-709typeA look profile? Any thoughts would be appreciated.
Click to expand...

Dave,
Personally, I don't think the LC-709typeA LUT looks very good (you can get a much nicer image with a custom Scene File), but if you must bake it in, put Zebra 2 at 90% and expose for bright white. However. if you do NOT bake-in the LUT, and just use it as a MONITORING LUT (as it was designed to be used by Sony), while you actually record the unadulterated SLOG3 signal, then make sure to expose bright white at 72% -- otherwise your S-LOG3 video will be overexposed.
But as I said, try using a Scene File rather than baking-in a LUT. None of the camera's LUTs or Look Profiles really looks very good. No professional colorist I know would use the LUTs in post, or worse, bake the in at the time of shooting. People seem to have lost sight that they are designed for monitoring, not to produce the best final image. Either grade in post from the unadulterated LOG footage, or use a custom Scene File. That's my advice.

http://www.vortexmedia.com/Guide-to-Sony-F55.html



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I disagree a little bit in the sense that if you were going to apply the LC709TypeA LUT in post and from there only need a minor tweak by the editor using some simple curves, etc. then it makes pretty good sense to bake it in if there is no budget or time to go through the process of pulling all the footage through Resolve and applying the same LUT that could be done in-camera. The quality of the LUTs in-camera are 33x33x33 latices which is pretty good and makes good results.

I'm not debating LC709TypeA vs. look profiles, only whether to bake in or not. But I do find the LC709ATypeA better looking than the other LUTs and it can be mixed with Alexa quite easily.
 
I agree that the LC709TypeA is "better looking" than the others, but, in my opinion, it still falls way short of producing a decent image. And if you're going to grade the footage anyway, why would you want to bake-in a LUT and limit your options in post? That approach doesn't make sense because it doesn't take any extra time or computing power to touch-up a baked in LUT vs. grading unadultrated S-LOG footage from scratch in Resolve.

And like I said before, if someone's goal of baking in a LUT is to avoid any grading in post -- then I know for a fact (from extensive testing) that you can absolutely do better with a custom Scene File. In my opinion, baking in one of the camera's built-in LUTs is never a good approach to getting the best image out of the camera.

http://www.vortexmedia.com/Guide-to-Sony-F55.html



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When I say grade LC709TypeA later, it means just a very small amount that an editor can do. Same as handing footage over in Hypergamma or Cinegamma. ie. pulling the blacks back down to proper levels, and maybe a small bump in the curve, but nothing beyond gamma adjustment grading. Stuff an editor can do without having to worry about pulling a good image from slog. Many clients don't want slog and baking in a LUT is perfect way to go, same as Alexa does it with REC709 LUT, and same now as Sony does it with their look profiles or hypergammas.

Now if I was skilled like you are at creating profiles in-camera, I might so be inclined to do so. But even the LUTs can be a good starting point for grading, better than S-Log to some respect.
 
By your logic you should also not tweak-grade a built in hypergammas either though, so I'm a bit confused what it is that you are against? Burning in a LUT of Look of native HG - or having to do a little grading tweak in post if you decide to bake anything in that gives a "look" in-camera which is not slog.

It's ok to disagree, it makes for good discussion. :beer:
 
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Thanks Dennis , Doug and Tomas for the spirited discussion! I can see good points on all sides of this conversation. As for me , I mainly work in the documentary world. Sometimes my clients have the time and budget for grading of the footage and sometimes they don't. If the budget does not allow for it, then I as a DP have to provided them with a quality, cinematic image that requires little to no grading for low cost and quick turn around.

I would love to exclusively shoot on Slog 2 or 3 but don't always have that luxury. As my camera is fairly new, I only have a handful of scene files loaded in it at this time. Most of them look somewhat video like. If you guys can recommend any scene file options I would love to hear them. In the meantime the LC-709typeA Look Profile while not perfect, gives a nice cinematic look that doesn't require a lot of intensive post production.
 
starcentral said:
By your logic you should also not tweak-grade a built in hypergammas either though, so I'm a hit confused what it is that you are against? :beer:
Click to expand...

That is correct. With a good scene file, there should be no tweaking necessary of the built-in Hypergammas. They can provide a very nice WYSIWYG finished look right out of the camera and ready for air with no further grading. And I will take a good scene file over Sony's ugly built-in LUTs anytime.

http://www.vortexmedia.com/Guide-to-Sony-F55.html



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