Shooting in RAW with Dual ISO

J

jedtrently

Member
Hallo,

When shooting RAW things like White Balance and ISO settings are not 'baked in' so you can adjust them in post, but when thinking about your camera settings, how much does your ISO level affect the RAW video you eventually receive? Is it best to stay at native or raise the ISO in search of more exposed image? Does ISO act the same way with RAW as it does with a non-RAW video format?

The EVA1 has a dual ISO system (One native at 800 and another at 1600 I think) and I wonder how much you are really gaining from this when shooting in RAW? How does RAW and dual ISO interact with each other on cameras generally and the EVA1 in particular?

Let's think about it practically: it's an exterior night time shoot, not many lights bar a few practical light sources like street lamps, sign lights and car headlights etc. You want to increase the exposure of your subject but you've got your iris wide open, no additional lights and want to keep shutter speed the same for whatever reason (there's motion and you want to achieve a style, or you're avoiding rolling shutter) so you choose to increase the ISO level. How much will you benefit from the dual iso capability, compared to shooting video in another format? Will you see a typical increase in the exposure on your monitoring screen?

I was reading that BM set a white point at each photosite for all it's RAW recording on their cameras, making it unable resolve any highlights above that point. Is this true for the EVA1?

Apologies for all the bombardment of questions, I wrote this as a sort of stream of consciousness. I've tried googling the answers but it comes up with a lot of photo raw stuff that doesn't really seem properly applicable.

Any help appreciated
 
Dual ISO means that the chosen ISO gain is analog- applied before the A to D conversion. The RAW image recording is digital which means that it is recorded after the A to D conversion. Therefore the RAW will be different for each base ISO in the dual ISO camera.
Hope that's clear...
 
jedtrently said:
When shooting RAW things like White Balance and ISO settings are not 'baked in'
Click to expand...

A clearer way to think about it is that in RAW you are recording the sensor's native white balance and native ISO.

Now a sensor with dual ISO has two native ISOs. It does this by having two wires going through each pixel, and each wire has a different gain running through it, as optitek said. Anyway, as I understand it you have to pick one of those native ISOs before recording in RAW.

When a camera is not recording in RAW and you are thumbing through various ISOs, I think this is how it works. I think it depends on the fact that TVs don't have 12 or 15 stops of dynamic range. That really, when you hold a light meter up to your monitor's pixels, you would measure something around 6 or 7 stops. That means that when you record a scene outside with 11 or 12 stops, with a sensor that can capture it all, that in post* you are remapping those 11 or 12 stops to 6 or 7. That means you are either throwing away several stops or bending them to fit. Part of that process is picking a midpoint among your 11 or 12 stops to be the midpoint in the 6- or 7-stop result. This setting is the ISO.

(I say 11 or 12, even though cameras with 13 or 14 stops are now common, because an outdoor scene with more than 11 or 12 stops is rare, even one with a mix of direct sunshine and deep shadow. Measure it!)

* By post I mean either at your computer or the camera itself, anything post conversion from analog to digital. Most videocameras do quite a lot of post (color correction, noise reduction) in their little bodies.
 
My suggestion for RAW shooting is to set the camera to the NATIVE ONLY mode for the ISOs and then switch between 800 & 2500 as appropriate. This will give the best image quality & flexibility as these settings do affect the RAW output. Ans I ALWAYS think that people should set the white balance appropriately when shooting RAW on any camera. This shifts data towards the color balance that you prefer, and increases your flexibilit in post, not decreases.
 
Mitch Gross said:
My suggestion for RAW shooting is to set the camera to the NATIVE ONLY mode for the ISOs and then switch between 800 & 2500 as appropriate. This will give the best image quality & flexibility as these settings do affect the RAW output. Ans I ALWAYS think that people should set the white balance appropriately when shooting RAW on any camera. This shifts data towards the color balance that you prefer, and increases your flexibilit in post, not decreases.
Click to expand...

optitek said:
Dual ISO means that the chosen ISO gain is analog- applied before the A to D conversion. The RAW image recording is digital which means that it is recorded after the A to D conversion. Therefore the RAW will be different for each base ISO in the dual ISO camera.
Hope that's clear...
Click to expand...

combatentropy said:
A clearer way to think about it is that in RAW you are recording the sensor's native white balance and native ISO.

Now a sensor with dual ISO has two native ISOs. It does this by having two wires going through each pixel, and each wire has a different gain running through it, as optitek said. Anyway, as I understand it you have to pick one of those native ISOs before recording in RAW.

When a camera is not recording in RAW and you are thumbing through various ISOs, I think this is how it works. I think it depends on the fact that TVs don't have 12 or 15 stops of dynamic range. That really, when you hold a light meter up to your monitor's pixels, you would measure something around 6 or 7 stops. That means that when you record a scene outside with 11 or 12 stops, with a sensor that can capture it all, that in post* you are remapping those 11 or 12 stops to 6 or 7. That means you are either throwing away several stops or bending them to fit. Part of that process is picking a midpoint among your 11 or 12 stops to be the midpoint in the 6- or 7-stop result. This setting is the ISO.

(I say 11 or 12, even though cameras with 13 or 14 stops are now common, because an outdoor scene with more than 11 or 12 stops is rare, even one with a mix of direct sunshine and deep shadow. Measure it!)

* By post I mean either at your computer or the camera itself, anything post conversion from analog to digital. Most videocameras do quite a lot of post (color correction, noise reduction) in their little bodies.
Click to expand...

Thanks foe those responses! Made things a lot clearer, especially by putting it in a pre/post A/D conversion sense. I always knew Cinema Cameras had far greater dynamic range than TVs but had never realised it in terms of 'shrinking' the dynamic range to accurately display your image on a TV - I suppose this is why HDR TVs & broadcasting such an exciting prospect for the future.

So, when recording RAW, I have the 2 native ISO settings to choose from and I can't deviate from these? (Or rather, deviating from these won't see any change or benefit) I seem to remember when shooting RAW on the RED One that I could dial through the ISO settings but can't recall whether the changes were actually making a difference in the exposure on the monitor.

All the best
 
To reiterate, always shoot to be best settings. ISO, WB, exposure. Raw is not a fix it in post tool that lets you just shoot and do what you like in post. Best settings are still the best settings.
 
You must log in or register to reply here.
Back
Top