Confusion about Floating Point in Color Space Transforms

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Mandem Junior Member • Posts: 28
Confusion about Floating Point in Color Space Transforms

My question is more from a Video/Color standpoint but since video is based on the principles of photography I figured perhaps someone could help(I've asked on the video forums as well)

To explain my confusion I'm going to use an example with a hypothetical sensor which clips at a max 1000% scene linear reflectance and crushes blacks at 0% light (I know there is no such thing as 0% light but it just makes the numbers easier to deal with).

I've attached below a hypothetical 10bit Log Transform and a 16bit Linear RAW graph of the Input of Linear Light and Code value output(The so called OETF). The output values are both in Code Value (and Normalized from 0-1)

Now, when the 10bit Log encoded image goes through a Color Space Transform the first thing that happens to it is that it gets "Linearized" to a 32bit Floating Point(this is Davinci Resolve) before any other thing happens to it. Now, I'm not a software developer or video engineer or anything of that sort but having read about Floating Point(which is much more confusing than integer values) it's been said that Floating Point allows for values greater than 1 and less than 0. The problem I'm having is understanding how does this relate to Scene Linear Reflectance getting matched to the output in Linear Floating Point? For instance is 100% light reflectance giving an output of 1(the highest possible value in integers)? Does a 500% reflectance give an output of 5?What about 1000% reflectance, would that be an output of 10 and would the graph end there?? Or am I completely way off and 1000% reflectance would still be an output of 1 just that between 0 and 1 there'd be approximately 4 billion values worth of data(then what's the point of having values greater than 1 and less than 0?)

The thing that's tricking me is that the entire dynamic range of the camera gets squeezed into a 0-1 range in the integer encoded camera files, but I can't understand what's happening with this Linearized 32bit Floating Point. How is this 32bit Floating Point any different than the Linear RAW(Other than it being 32 bit rather than 16 bit?). What's the significance of having values greater than 1 and less than 0? Just very lost on this. Thanks

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