dentro la scuola che cambia con la fotografia

Posts con tag ‘techniques’

HDR: fantasy or reality?

What is the first thing that comes to your mind when you hear HDR? Something unreal or maybe something real. Let’s start making a few points clear. The set of techniques that allow to have more or greater dynamic range of luminance between the darkest and the lightest areas of an image is called High Dynamic Range Imaging (HDRI or just HDR) and is usually  used to fix a too-extreme range of luminance.

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There are many ways to get an HDR image, in 1850s Gustave Le Gray combined 2 negatives in a single picture in positive to get a seascape with details in the sky and details in the sea. Early as the 1930s and 1940s was originally developed by Charles Wyckoff who implemented local neighborhood tone remapping to combine differently exposed film layers into one image of higher dynamic range. In the mid-century manual tone mapping it was common using dodging and burning that means manipulate in the darkroom at the moment of print. Ansel Adams wrote a book on producing prints called The Print and elevates this 2 techniques to an art form.

Underexposed picture (Javier Rodriguez)

This techniques were not possible with the advent of color films due to the specific timing required during the developing process. For many years HDR was well accepted but precluded by the limitations imposed by the available computer processing. In 1985 Gregory Ward created the Radiance RGBE image file format which still the most commonly HDR imaging file format and in subsequent years the Wyckoff’s concept was applied to video cameras. In the 90s HDR uses a completely different approach, based on making a high dynamic range luminance or light map across the entire image and then tone mapping this result, this method produce a HDR from a  set of images taken with a range of exposures and may be of lesser or greater quality than an image from a single exposure of a sensor that has a native high dynamic range. Also in this years the new demand produced by the digital camera consumers forced to develop new technology to create sensors with more dynamic range.

Overexposed picture (Javier Rodriguez)

Yet at the same time Steve Mann developed and patented the Global-HDR method which is the same that is usually used today and it was presented to the public in 1997 by Paul Debevec. Since that time many software producers have developed many softwares to create HDR images, at the beginning were just basic tools and adjustments to fix the problems with too-extreme range of luminance. Then they were improved: now this technology is available also on smartphones.

HDR picture (Javier Rodriguez)

Now there’s nothing more than say, just that the perspective with which the man sees the world goes hand in hand with technology. What at first was a tool to give a picture a sense of reality now became a tool to make fantasy worlds.

Javier Rodriguez