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High Dynamic Range Photography, and Use in Eye Emulation

H.D.R., or high dynamic range photography is a relatively new technique used by photographers to take high-quality full lighting range photos that are near-indistinguishable from paintings, for their ability to correctly replicate the lighting of a given scene, exactly how the human eye would see it.

Dynamic range measures how great a difference between light and dark can be captured by a digital camera. No camera, digital, or analogue made thus far, has ever even come anywhere near the power of the human eye for taking in all luminosity ranges in a scene. To prove this, think about any photograph you have ever taken of a room's interior while still capturing the view outside its windows. You either get a blurry outside, or a blurry inside, depending on which range you focus on.

Basically, a camera's luminosity range is very narrow, and cannot process the amount of data necessary with variation in light levels over the entire visible spectrum. HDR tries to fix this issue by acknowledging the camera deficiencies and taking a number of photographs of the exact same scene, each with the luminosity range of the camera altered, so it focuses on different light levels each time.

Digital image filters then merge all the separate photographs into one, to running from underexposures to over exposures, and everything in-between. These are then combined to calculate the full dynamic range of the view. This, final image is then roughly equivalent to what the human eye sees when it scans a physical scene.

Major Problems

HDR is far from perfect as a method for recreating images to the same fidelity as the human eye. One of the greatest limitations is alignment. When multiple images are overlapped, a single image that is too far out of alignment creates a blurry image.

Motion capture with HDR is impossible. Rippling water, or a wind strong enough to rustle leaves will create distorted, blurred images for the same alignment reasons.

Lastly, and perhaps most critically, there is presently no standard ocular display - monitor, HMD, or projector, capable of displaying the full range of luminosity the human eye can process - for the exact same reason as cameras not being able to take images of the same luminosity range.

In theory, direct-retinal projection should be able to bypass this problem, but as of writing, no-one has considered hooking a HDR display to a retinal projection system, to test the colour-balance and realism of the image. If the result is even 50% more realistic than a monitor-display, this technique would revolutionise QTVR and similar systems.

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