Native ISO for video

[jwang88]

I just wonder why the native ISO on video camera is much higher than still camera, most of them start at ISO 800+ and make the ND is a must while shooting under bright sunlight. But on most dslr or mirrorless cameras the lowest ISO setting is the same between the still and video so I can set the video ISO as low as ISO100. I think it is not the native ISO and it must be pulled electronically inside the camera. Am I right?

 

[pgb]

The Arri Alexa refers to a native ISO of 800 but you can go to 100. The Sony A7s won't go lower than 3200 with log enabled but I think that's just protecting their other products. It's a good question, I would like to understand this too.

 

[justgo99]

The Arri Alexa refers to a native ISO of 800 but you can go to 100. The Sony A7s won't go lower than 3200 with log enabled but I think that's just protecting their other products. It's a good question, I would like to understand this too.

I'm not entirely sure about this, but I have a pretty good idea of it.

There are basically 2 possible reasons. 1. is the native sensor ISO, which is a pretty simple concept. It's basically the native ISO for the sensor, so for instance 200 for m4/3 and fuji or 100 for Canon and Nikon and much higher ones for other cinema cameras.

But in terms of video, the 'native' ISO is actually artificially deduced. Most pro cameras natively utilise something called a 'log' profile. It's basically just a flatter looking profile used to gain extra dynamic range in the shot. What it does is (I think) it raises the shadow gamma by actually raising the ISO up and then compresses the highlights to prevent blowing them out. So in short it raises the shadows, lowers and compresses the highlights, and then takes the ISO reading from the shadows. That's what I read somewhere. Now why is the Sony native ISO for Slog 1600 or so compared to V-Log's 400? I'm not sure about that, but it's to do with the way the log curve was actually developed and how it ties in with the sensor. I'm pretty sure it's not just a marketing thing.

Hope that helps a bit.

 

[Vesku]

The Arri Alexa refers to a native ISO of 800 but you can go to 100. The Sony A7s won't go lower than 3200 with log enabled but I think that's just protecting their other products. It's a good question, I would like to understand this too.

I'm not entirely sure about this, but I have a pretty good idea of it.

There are basically 2 possible reasons. 1. is the native sensor ISO, which is a pretty simple concept. It's basically the native ISO for the sensor, so for instance 200 for m4/3 and fuji or 100 for Canon and Nikon and much higher ones for other cinema cameras.

But in terms of video, the 'native' ISO is actually artificially deduced. Most pro cameras natively utilise something called a 'log' profile. It's basically just a flatter looking profile used to gain extra dynamic range in the shot. What it does is (I think) it raises the shadow gamma by actually raising the ISO up and then compresses the highlights to prevent blowing them out. So in short it raises the shadows, lowers and compresses the highlights, and then takes the ISO reading from the shadows. That's what I read somewhere. Now why is the Sony native ISO for Slog 1600 or so compared to V-Log's 400? I'm not sure about that, but it's to do with the way the log curve was actually developed and how it ties in with the sensor. I'm pretty sure it's not just a marketing thing.

I can do the same with my GH4. Shooting with iso200 and using image settings to raise shadows so that the image looks like it was shooted with iso 1600 but the highlights are still not clipping. It is like using iso200 for highs and iso1600 for shadows at the same time.

The image may look dull and noisy if using these extreme settings but sometimes it can give good results.

 

[pgb]

The Arri Alexa refers to a native ISO of 800 but you can go to 100. The Sony A7s won't go lower than 3200 with log enabled but I think that's just protecting their other products. It's a good question, I would like to understand this too.

I'm not entirely sure about this, but I have a pretty good idea of it.

There are basically 2 possible reasons. 1. is the native sensor ISO, which is a pretty simple concept. It's basically the native ISO for the sensor, so for instance 200 for m4/3 and fuji or 100 for Canon and Nikon and much higher ones for other cinema cameras.

But in terms of video, the 'native' ISO is actually artificially deduced. Most pro cameras natively utilise something called a 'log' profile. It's basically just a flatter looking profile used to gain extra dynamic range in the shot. What it does is (I think) it raises the shadow gamma by actually raising the ISO up and then compresses the highlights to prevent blowing them out. So in short it raises the shadows, lowers and compresses the highlights, and then takes the ISO reading from the shadows. That's what I read somewhere. Now why is the Sony native ISO for Slog 1600 or so compared to V-Log's 400? I'm not sure about that, but it's to do with the way the log curve was actually developed and how it ties in with the sensor. I'm pretty sure it's not just a marketing thing.

I can do the same with my GH4. Shooting with iso200 and using image settings to raise shadows so that the image looks like it was shooted with iso 1600 but the highlights are still not clipping. It is like using iso200 for highs and iso1600 for shadows at the same time.

The image may look dull and noisy if using these extreme settings but sometimes it can give good results.

That's about it. After doing some more searching -

`What they mean by that is that 800 gives the best compromise between highlight handling at the top and noise at the bottom. The available bits are distributed more or less evenly from darkest to brightest'

Lower iso gives better noise performance but the latitude distribution above and below
an 18% grey card mid reference point is uneven.

`the digital cinema cameras can't treat ISO the same way stills cameras do'

EI 160 (+5.0 / -9.0) EI 200 (+5.3 / -8.7) EI 400 (+6.3 / -7.7) EI 800 (+7.4 / -6.6) EI 1600 (+8.4 / -5.6) EI 3200 (+9.4 / -4.6)

http://www.cinematography.net/edited-pages/Optimal ISO for Alexa.html