Raw view mode match 320 ISO

[Gabriele Turchi]

I was testing the raw mode (for exposure ) and I know that the raw mode is not truly raw (otherwise would be linear light ) and my understand is that the raw mode turn off the metadata and color matrix , but what i have realized is that raw mode use 250 ISO , and I was expecting that the raw mode was using 800 Iso (native iso of the sensor )

Does anyone knows why the raw mode use 250 ISO?

As proof setting the camera to 250 ISO and switching between raw mode or normal mode the image only change in saturation and white balance , but having the amer set to 800 ISO the raw mode looks darker (as the 250 ISO)

Thanks

g

 

[Eric Haase]

The "native" sensitivity of the sensor seems to be 320. But at 320 the dynamic range distribution of shadows versus highlights heavily favors range in the shadows and compromises highlights. Because the noise floor is so low with the sensor, it is possible (and recommended) to rate the camera 800, which essentially shifts the mid grey point more into the shadows providing more highlight headroom and a more even (but not equal) distribution of shadows and highlights over the dynamic range of the sensor.

 

[Terry VerHaar]

Eric - Very nice explanation. I sort of understood all that previously but could never describe it succinctly. Great job. Thanks!

 

[Ryan Fitzgerald]

Yeah Eric, great explanation. Thanks

 

[Gabriele Turchi]

The "native" sensitivity of the sensor seems to be 320. But at 320 the dynamic range distribution of shadows versus highlights heavily favors range in the shadows and compromises highlights. Because the noise floor is so low with the sensor, it is possible (and recommended) to rate the camera 800, which essentially shifts the mid grey point more into the shadows providing more highlight headroom and a more even (but not equal) distribution of shadows and highlights over the dynamic range of the sensor.

Thanks eric ,

this is valid for both low light and bright daylight shooting ?

i understand that because of low noise staying at 800 protect highlight with no more noise introduced etc... but i don't get why if the native is 320 , on bright daylight shoot , shooting at 320 would not properly distribute the image across the sensor ...

isn't this "rate at 800" only to protect highlight and noting more than that ?

thanks

g

 

[Eric Haase]

Thanks eric ,

this is valid for both low light and bright daylight shooting ?

i understand that because of low noise staying at 800 protect highlight with no more noise introduced etc... but i don't get why if the native is 320 , on bright daylight shoot , shooting at 320 would not properly distribute the image across the sensor ...

isn't this "rate at 800" only to protect highlight and noting more than that ?

thanks

g

You can rate the camera at 320 and shoot in day exterior. But you will see that you have more stops below middle grey (shadows) and few stops above middle grey (highlights) before clip. This is just the way the sensor was designed I suppose. You should test it and compare it to shooting the same series of exposures at 800. At 800, where middle grey lies on the raw sensor data is moved toward the shadows and the 800 ISO metadata brings it up to look like actual middle grey. This allows for more range in the highlights. I don't think of it as "protecting" the highlights as much as taking advantage of more dynamic range in the highlights, because even at 800 I will often have highlights that clip out on the raw sensor data. Rating at 800 gets you closer to an even distribution of highlights and shadows. If you want true even distribution you will have to rate around 1280.

If you have a scene- for example a night interior- where all of the tones in the scene should lie 2 stops over middle grey at most and below, then rating 320 might be a good choice. By doing so you will fill more of the range of the raw sensor rather than underexposing a lot off shadows by rating 800. The best use of this would be if you desire a very dark scene where all tones are below middle grey. This allows the lowlights to be less noisy than rating 800 for a scene of this type. By exposing this way, you will have more flexibility in post to manipulate the image. Having said this, I've shot night exteriors that have values in the scene at key and below and rated 800 or 1000 and have achieved great results, mostly because I knew I wouldn't want to make the scene brighter or push the grade very far. I've recently been grading this footage in a 2K DI suite on a 30 foot screen and have not needed to use any noise reduction.