How Red's HDRx works and how does it differ from Magic Lantern's HDR video?

[VlastaS]

I was just wondering how Red's HDRx works and how does it differ from Magic Lantern's HDR video? They say that there it records to tracks of video simultaneously, without time gap between properly exposed frames and what they call highlight protection. They also say that ISO and Shutter speed/or angle don't change. How does it work then?

[Roman]

As best I know, cameras like that effectively take a 'raw' file (like Canon cameras can do for photos) each frame.

So all of the highlights, shadows etc are available in post processing to get the desired look.

As well as that I think they shoot at a resolution much bigger than 1080p, so if they wanted to zoom or pan in post processing they could still have 1080p without necesarily any quality reduction.

Theoretically you could take a similar shot with a Canon camera, but its definitely a lot more forgiving if you get things wrong with a camera like that... But you'd hope so, given the price difference!

[KarateBrot]

who said that shutter speed does not change? as far as i know HDRx works with two video streams recorded simultaneously but with different shutter speeds. since it's an electronic camera it's not a problem to record with different shutter speeds simultaneously. the sensor just needs to be exposed by light. the electronic signals can be buffered. once the exposure for the slow shutter speed is finished the buffered data gets passed along to stream A but without deleting the buffer. now the sensor gets exposed until the long exposure is finished. now this data goes to stream B. now the buffer can be cleared to record a new frame. this way you end up with two video streams. and as far as i know these two streams get merged to HDR on the computer with the red software.

[3pointedit]

Also I would expect that they are taking the second frame immediately behind the first, not half way between 1st and 3rd. That should reduce temporal mismatch of images.

[KarateBrot]

That's what i meant. let's explain it with film. the film frame gets exposed by light. half way through the exposition process the frame gets doubled and put to stream A. after the whole exposition process the original frame gets put to stream B. this way you get 2 frames which started to get exposed at the same time.
in theory you can get an infinite spectrum of exposed frames this way even though you only exposed 1/48th of a second for example.
that's the cool thing about an electronic sensor. you can record at several shutter speeds at the exact same time with only one sensor.

edit: i wonder if some day our cool ML crew has got so much control over the camera so that this is technically possible. but it's already capable of more than i have ever dreamt of