HDR

HDR stands for High Dynamic Range image

A ‘HDR’ image, as taken by the Spheron system contains 32-bits of information, offering an almost limitless data range for color and luminance (brightness).

To explain what 32-bit means in relation to an image, lets start with a 1-bit image.

‘1’ bit would equal 2 to the power of 1 = 2 or 2 x 1 = 2

This would allow 2 tones – eg Black or White

‘4’ bit would equal 2 to the power of 4 = 16  or 2 x 2 x 2 x 2

This would allow 16 tones

Therefore:

  • 1 bit = 2 levels (black and white)
  • 4 bit = 16 colors / greyscale tones
  • 8 bit = 256 colors / greyscale tones
  • 16 bit = 65536 colors / greyscale tones
  • 32 bit = approx. 4.3 Billion color / greyscale tones

For reference, the human eye is perceived to register about 10 million colors.

HDR images are used for two main applications

  • Photography – to provide extra color / luminance range in the image*
  • CGI Rendering (Computer Rendering) via a process called Image Based Lighting (IBL)

* In reality, to actually appreciate this information as a print or via screen, the image is often ‘tone-mapped’

To understand how the Spheron system captures a HDR image, read more here:

Spheron HDR capture process

f-stops and exposure

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