   HDR
  Im having a little trouble understanding HDR in general. I understand that by using HDR compatible Frame buffers/render targets, you are able to store a higher range of light values, but I have a number of questions.1. If with normal rendering, values are only stored between 0.0f-1.0f, which later get mapped to 0-255. When using HDR targets, which can store floating point values of positive and negative values, what is classed as completly black? is it 0.0f? or a negative value?2. What adjustments need to be made to your scenes lights if any? I'm thinking no adjustments are made, you are just able to have light values above 1.0f for special effects.3. From my understanding, your frame buffer can become full of values of over 1.0f, Such as in the case where the player walks from inside a dark room to a brightly light outside enviroment. This effect simulates a real persons eyes  by having a slower shutter speed on the camera indoors (due to it being dark), which causes blow out when going outside. Whilst this effect is desired, the application also needs to gradually correct the exposure times to a correct mapping to resolve the blowout, so we can see outside enviroment, as our eyes do in real life. I believe this part of simulation of exposure times is refered to as tone mapping. Where you take the average luminance of the HDR image, and use this to scale the image to a 0-255 per channel image. So does this mean that if i had HDR frame buffer of evenly spaced values between lets say 5.0f and 10.0f, then somewhere around 5.0f would be mapped to 0, and somewhere around 10.0f would be mapped to 255?What I dont understand here, is that if our HDR buffer contained all mostly very dark values to simulate night, would this then be mapped to the range 0-255, making the scene then appear lit as in daylight?   