This is another one from Social Media and it the same question gets asked a lot. The short answer is…………
Even with Sony’s earlier S-Log3 cameras you didn’t need to ALWAYS over expose. When shooting a very bright well lit scene you could get great results without shooting extra bright. But the previous generations of Sony cameras (FS5/FS7/F5/F55 etc) were much more noisy than the current cameras. So, to get a reasonably noise free image it was normal to expose a bit brighter than the base Sony recommendation, my own preference was to shoot between 1 and 1.5 stops brighter than the Sony recommended levels (click here for the F5/F55, here for the FS7 and here for the FS5).
The latest cameras (FX30, FX3, FX6, FX9 etc) are not nearly as noisy, so for most shots you don’t need to expose extra bright, just expose well (by this I mean exposing correctly for the scene being shot). This doesn’t mean you can’t or shouldn’t expose brighter or darker if you understand how to use a brighter/darker exposure to shift your overall range up and down, perhaps exposing brighter when you want more shadow information and les noise at the expense of some highlight range or exposing darker when you must have more highlight information but can live with a bit more noise and less shadow range.
What I would say is that exposure consistency is very important. If you constantly expose to the right so every shot is near to clipping then your exposure becomes driven by the highlights in the shot rather than the all important mid range where faces, skin tones, plants and foliage etc live. As the gap between highlights and the mids varies greatly exposure based on highlights tends to result in footage where the mid range is up and down and all over the place from shot to shot and this makes grading more challenging as every shot needs a unique grade. Base the exposure on the mid range and shot to shot you will be more consistent and grading will be easier.
This is where the CineEI function really comes into its own as by choosing the most appropriate EI for the type of scene you are shooting and the level of noise you are comfortable with and basing the exposure off the image via the built in LUT will help with consistency (you could even use a light meter set to the ISO that matches the EI setting). Lower EI for scenes where you need more shadow range or less noise, higher EI for scenes where you must have a greater highlight range. And there is no -“One Fits All” setting, it depends on what you are shooting. This is the real skill, using the most appropriate exposure for the scene you are shooting (see here for CineEI with the FX6 and with the FX9)
So how do you get that skill? Experiment for yourself. No one was born knowing exactly how to expose Log, it is a skill learnt through practice and experimentation, making mistakes and learning from them. In addition different people and different clients will be happy with different noise levels. There is no right or wrong amount of noise. Footage with no noise often looks very sterile and lifeless, but that might be what is needed for a corporate shoot. A small to medium amount of noise can look great if you want a more film like look. A large amount of noise might give a grungy look for a music video. Grading also plays a part here as how much contrast you push into the grade alters the way the noise looks and how pleasing or objectionable it might be.
All anyone on here can do is provide some guidance, but really you need to determine what works for you, so go out and shoot at different EI’s or ISO’s, different brightness levels, slate each shot so you know what you did. Then grade it, look at it on a decent sized monitor and pick the exposure that works for you and the kinds of things you shoot – but then also remember different scenes may need a different approach.