Why need we change ISO for lighter picture if we get the same RAW file anyway?

[Datsenko Alexey]

Guys, tell me please,
every DP when is darking trying to make picture more lighter and change ISO from 320 to 800 for example, and the pictire is becoming lighter at the monitor, but monitor is just some preset, rec709 for example, but actually we get the same RAW picture with ISO 320 and with ISO800 it is the same RAW picture, for example when I see at these two pictures with ISO 320 and ISO 800, I can't find in RAW view that picture with ISO 800 is lighter then with ISO 320, it is seems the same pictures.
So why everybody is trying to make picture lighter changing ISO to 800 if we will work with RAW files in the future and I think we can change ISO on postproduction actually?
So why need we change ISO to get picture more lighter?
Thanks

 

[Martin Konrad]

hello Datsenko,
I really hope its not every DP you meet working like that...
You are right the Raw image does not change and no additional light is hitting the sensor.
A lot of people coming up from the 5d/Sony a7 world where iso works differently and frequently
underexpose the Red sensor.

In short you have 3 options if light drops
- add light (projectors/reflectors)
- open the aperture
- fix it in post (higher ISO/ live with more noise/ noise reduction in post)

 

[Björn Benckert]

hello Datsenko,
I really hope its not every DP you meet working like that...
You are right the Raw image does not change and no additional light is hitting the sensor.
A lot of people coming up from the 5d/Sony a7 world where iso works differently and frequently
underexpose the Red sensor.

In short you have 3 options if light drops
- add light (projectors/reflectors)
- open the aperture
- fix it in post (higher ISO/ live with more noise/ noise reduction in post)

Increase Exposure time is also a possibility.


But yes changing iso around in camera does not improve / change anything. Its like changing brightness on the screen.

 

[Martin Konrad]

of course you are right about exposure time if there is no light you have to make a compromise somewhere...

 

[Sean Keen]

Iso controls:

1 Grain,
2 Dynamic range

nothing else