Film and digital imaging systems can capture anywhere from 1 to 15 EVs, but our eyes differ in two significant ways: adaptation and non-linear response. Our eyes are able to see upwards of 25 EVs of tonal range, depending on the lighting conditions. “EV” is often used interchangeably with “stop” or “f-stop,” though strictly speaking the latter terms refer specifically to the opening of the lens, while EV applies to both shutter speed and aperture. This is simply a measurement of how much light is coming through a lens and hitting a sensor, be it film, a CMOS chip, or your retinas. When we’re talking about photography, we measure light in terms of Exposure Values (EV). In this case the HDR file was merged from a sequence of five separate exposures from 1/30 to 2 seconds, then tone mapped in Photomatix Pro. These tone mapping applications, called Tone Mapping Operators (TMOs), can be stand-alone programs or plug-ins within another application such as Photoshop or Aperture.įigure 1 The “HDR” images we see on the web and in print are really low dynamic range images that have been compressed from an HDR file using a tone mapping operator. The HDR file is then “tone mapped” back into an LDR image that can be displayed and printed. Shooting HDR scenes with conventional digital cameras requires photographing a sequence of exposure-bracketed Low Dynamic Range (LDR) captures, and then using specialized software to merge them into a single HDR file. Specialized software (tone mapping operators or TMOs) is used to compress the greater tonal range of HDR images into a tonal range that can be displayed on conventional monitors or printed. HDRI can far surpass the dynamic range restrictions of traditional chemical and digital photography, and can more accurately be used to recreate a scene in terms of how human vision works. High Dynamic Range Imaging (HDRI) is an imaging technology developed to capture the entire range of light present in a scene.
0 Comments
Leave a Reply. |