I’ve covered this many, many times before, but so many people still struggle to get their head around using the CineEI mode in a Sony camera.
Shooting using CineEI is a very different process to conventional shooting. The first thing to understand about CineEI and Log is that the number one objective is to get the best possible image quality and this can only be achieved by recording at the cameras base sensitivity. If you add in camera gain you add noise and reduce the dynamic range that can be recorded, so you always need to record at the cameras base sensitivity for the best possible “negative” or captured image.
Sony call their system CineEI. On an Arri camera the only way to shoot is using Exposure Indexes and it’s the same with Red, Canon and almost every other digital cinema camera. You record at the cameras base sensitivity.
It is assumed that when using CineEI that you will control the light levels in your shots to levels suitable for the recording ISO of the camera, again it’s all about getting the best possible image quality.
Then changing the EI allows you to tailor where the middle of your exposure range is and the balance between more highlight/less shadow or less highlight/more shadow detail in the captured image. On a bright high contrast exterior you might want more highlight range, while on a dark moody night scene you might want more shadow range.
EI is NOT the same as ISO.
ISO= The cameras sensitivity to light.
EI = Exposure Index.
Most cine film stocks had both an ISO rating, where the ISO was the laboratory measured sensitivity and an Exposure Index which was the recommended value to use in a light meter to obtain the best results in a typical practical filming situation. More often than not the ISO and EI values were slightly different.
EI is an exposure rating, not a sensitivity rating. EI is the number you would put into a light meter for the best exposure for the type of scene you are shooting or it is the exposure value of the LUT that you are monitoring with. The EI that you use depends on the desired shadow/highlight range and it is more often than not unwise to raise the EI in a low light situation.
A higher EI than the base ISO will result in images with less shadow range, more highlight range and more noise. This is not what you normally want when shooting darker scenes, you normally want less noise, more shadow range. So with CineEI, you would normally try to shoot a darker, moody scene with an EI lower than the base ISO.
This goes completely against most peoples conventional exposure thinking. But the CineEI mode and log are not conventional and require a completely different approach if you really want to achieve the best possible results. If you find the images are too dark when the EI value matches the recording base ISO, then you need to add light or use a faster lens. Raising the EI to compensate is likely to create more problems than it will fix. It might brighten the image in the viewfinder, making you think all is OK, but you won’t see the extra noise and grain that will be in the final images once you have raised your levels in post production on a small viewfinder screen. Using a higher EI and not paying attention could result in you stopping down a touch to protect some blown out highlight or to tweak the exposure when this is probably the last thing you want to do.
I’ve lost count of the number of times I have seen people cranking up the EI to a high value thinking this is how you should shoot a darker scene only to discover they can’t then make it look good in post production. The CineEI mode on these cameras is deliberately kept separate from the conventional “custom” or “SDR” mode to help people understand that this is something different. And it really does need to be treated differently and you really do need to re-learn how you think about exposure.
The CineEI mode in some regards emulates how you would shoot with a film camera. You have a single film stock with a fixed sensitivity (the base ISO). Then you have the option to expose that stock brighter (using a lower EI) for less grain, more shadow detail, less highlight range or expose darker (using a higher EI) more grain, less shadow detail, more highlight range. Just as you would do with a film camera.