Benjamin de Menil wrote:Why would anything other than 400 and 3200 - the two native ISOs - be useful at all when shooting RAW? ... except for monitoring
When shooting raw, you have the two modes: the low range and the high range. They are two different shooting modes on the camera.
Regardless of what ISO you set up to 1000, you're in the 100-1000 range. You can change the ISO at your own discretion in post within that range. If you shoot at ISO 400, Resolve won't let you select ISO 1600 in post, since that is in the high ISO range (starting from 1250).
If shooting raw, when selecting ISO, think of it more as rating the camera or scene, because the ISO you set might influence your choice of aperture (and maybe shutter). Changing ISO in post will never effect the amount of light you capture while shooting, but setting ISO before shooting might do so, by influencing you to open up or close down (actually changing how much light the sensor gets)—this is why it's important to consider ISO even if "it's just meta data".
If you default to rating your camera at ISO 400. but then you feel the image is more than a stop too dark at your selected aperture/shutter settings, consider going into the high range by re-rating it to ISO 1250.
Try to feed your sensor as much light as possible. That said, I'm not a fan of stopping down to save a specular highlight from blowing out (0.5% of the frame) just to severely under expose 99.5% of the scene.