ISOless Fujifilm X-T2

Propheticus wrote:

Am I right to understand, for RAW, limiting ISO to boost exposure in post only works properly in a manual mode?

Manual mode guarantees you full control. It could be argued that manual mode is the most straightforward approach, if you're in challenging conditions, want to get the most out of your files and have the luxury to use Manual.

For example, If I'd shoot Aperture Priority mode and then set autoISO to 160base ISO, 1600max ISO, 1/125s min SS.

If you're in one of the priority modes you're essentially letting the camera chose either the aperture or the shutter speed, i.e. the camera controls one of the exposure parameters. It generally does a pretty good job, but depending on the complexity of the scene and the metering mode you have set, the camera can fail to provide the desired exposure.

Generally, if something like that happens, you can switch on the auto exposure lock (AE-L) in order to stop the camera from making further exposure calculations and  use the exposure compensation wheel to lower or raise the exposure to the desired level.

However, if you're dealing with very complex lighting like the one present in the above posted church example, but have to also adequately capture multiple subjects, like in the above posted church, i.e. you want to retain all the possible church details and have to set a high enough SS to freeze the people inside the church, manual ISO with aperture priority and exp. comp. is (IMO) the way to go.

In darker situations the restriction in upper ISO would lead the camera to dip (far) below the set minimum SS to still reach a proper exposure.

The camera will dip under the minimum SS only if it is capped out at ISO 1600 and it's metering the scene as too dark. Again, if you need a higher shutter speed that what the camera suggests, just use the exposure comp. dial to get it to where you need it to be.

Looking at this chart is there a difference (A and SS being equal) between me limiting iso to 1600 and boosting exposure in RAW postediting -VS- simply using a higher ISO as needed up to 12800? I'd expect not. Also for Dynamic range, boosting exposure in post also smashes values into upper ranges, increasing the 'floor' and reducing DR. Or am I woefully mistaken?