Let Me Show You What HDR Photography Is All About And The
Techniques Used For Producing High Dynamic Range Photos
HDR photography is the common term for images with a range of detail
not normally possible with ordinary photographs.
The acronym HDR stands
for High Dynamic Range, a phrase borrowed
from the specialist field
of technical imaging, and now applied to a set of techniques designed
to overcome the key limitation of photographic film and digital image
sensors - their narrow sensitivity to light compared to the images
perceived by our eyes and brain.
In recent years HDR photography has grown from an obscure art into a
mainstream style. New software techniques and the boom in the use of
digital cameras have combined to create an often distinctive class of
photographic image that is now widespread in magazines, advertising,
online media, and even many Hollywood movies.
HDR photography manipulations can be
subtle, to improve the details in a photograph without creating an
unnatural effect - or they can be exaggerated, to create images with
almost impossible levels of detail that can appear dreamlike,
When imaging specialists talk about High Dynamic Range, they mean
something different than the common use of the term today. True HDR
images are captured with specialist HDR cameras that record the light
level of each pixel with very fine accuracy, resulting in an image that
can closely represent the true luminance of each part of the scene.
real life the ratio of luminance between
the darkest part of a scene
and the brightest part can be as much as 100,000:1.
The human visual
system can resolve ratios as high as 16,000:1, but only thanks to some
very clever tricks performed by eyes and the brain.
cameras, and some types of transparency film, can capture scenes with
ratios as high as 5000:1 or more. But the sensors on a good digital
camera will usually give a dynamic range of only between 1000:1 and
Why Is What The Eye Sees Different To What The Camera Sees?
The differences between what the eye sees and what a camera sees are
familiar to most photographers - a portrait shot taken in bright
sunlight might look
okay through the viewfinder, but produce a photograph spoiled by being
either too dark in the shadows or too bright in the light.
is also common in landscape photography, where the dynamic range
between the sky and the landscape can be very high. A photographer has
to choose the exposure to capture the detail of either the sky or the
landscape - or compromise, and lose detail in both.
Arenal Volcano, Costa
By Isaac Bordas, Creative Commons License
An image in the human visual system is created by the brain from a
series of "samples" recorded by the eyes, which move rapidly and
unconsciously when looking at any scene.
As the eyes view different
parts of a scene they can quickly adjust to different light levels by
varying the aperture of the pupil. The brain is continually processing
samples from the eyes into a composite visual map of a scene, which is
perceived as a detailed image with a high dynamic range.
on the other hand, are usually only exposed once, and often a
photographer faces the choice of exposing the shot to capture the
bright highlights of a scene and losing detail in the shadows, or
exposing for the shadows and blowing out the highlights.
with through-the-lens (TTL) exposure meters have different ways of
calculating a sweet spot for the exposure
of a photograph, but the
problem remains: a camera can only resolve a fraction of the dynamic
range resolved by the human visual system.
The common methods of
reproducing photographs create further problems - the dynamic range of
an LCD screen, or the paper used to print digital photographs, is about
half that of a digital camera.
Techniques of HDR photography
HDR photography techniques aim to bridge the gap between what the eye
sees and what the camera sees.
There are several ways of achieving
this, but the most common way is to use the data from several digital
exposures to make a single photograph with the widest possible range of
This is a rough approximation of how the eyes and brain
create the perception of high-dynamic range - capturing detail at
different exposures, and then combining the details into a single
Film photographers have long used HDR-like techniques
to improve their images. Split neutral density filters can be used to
darken the sky in landscape shots, and darkroom techniques such as
burning and dodging can manipulate the exposure of printed photographs.
In the 1850s the pioneering French photographer Gustave
Le Gray first
used multiple exposures to create images of seascapes - using one
negative for the sky, and another with a longer exposure for the sea,
and combining the two negatives to make a single photograph in
Thanks to modern digital cameras and imaging software the
process of combining several images is now relatively straightforward.
Many photo-editing applications and some cameras have functions to aid
the creation of HDR photographs, which has fostered the current
popularity of HDR images among amateur and professional photographers.
Because these images are taken with standard cameras and usually
reproduced on a computer screen or printed paper, they are not "true"
HDR images: technically they are Low or Standard dynamic range (LDR and
SDR) with an idealised distribution of the lighting range across the
image, giving the appearance of greater range.
But the term HDR has now
stuck fast to this type of photography - and especially to the sort of
brightly coloured, highly-detailed landscapes and cityscapes beloved by
many digital HDR photographers.
boat on the
Hudson River, New York state, USA
By Andy Milford, Creative Commons License
The two images above illustrate the effect of combining multiple
The image on the left is the result of one mid-range
exposure of the scene, and the image on the right is an HDR composite
of three exposures of the same scene, taken with different aperture
openings or shutter speed to vary the duration of the exposures.
this method it is common to make three exposures of every scene: a
mid-range exposure, an exposure one or two stops higher the first, and
an exposure one or two stops lower than the first.
The HDR photograph
on the right shows more visible detail than the single mid-range
exposure: the old wood of the boat appears bright and distinct in the
HDR, and the trees and buildings of the shoreline show a greater range
of contrasting detail.
Many digital SLR cameras have a bracketing function that can be set to
exposure automatically for each shot of the same scene, and it is also
possible to combine more than three exposures into a single HDR
It is important that the framing for each exposure should
be identical, although cropping and "stitching" with photo editing
software can fix small differences. Using a tripod for the camera is
practically essential, and using a shutter remote is ideal.
Post-processing HDR Photographs
The multiple exposures are merged into a single HDR file using either
photo-processing software, or sometimes using software within the
Adobe Photoshop versions after CS2 have a merge to HDR
function, and there are also specialist HDR editing applications
available, such as Photomatix
Pro and Dynamic
technique called tone mapping is then
used on the merged file to
combine the light and dark details into a single photograph to produce
the effect of a high range of detail and colour. Tone-mapping can also
be used to manipulate the colours of a single exposure, to produce
images with exaggerated local contrast for artistic effect.
By Andrés Nieto Porras, Creative Commons License
usually the method used in compact cameras and smart phones that have
an HDR mode, but it is also effective with digital SLRs that shoot
images in RAW format, which can be used to create various exposures of
a single shot.
This method avoids artefacts that can appear when
different exposures are combined, such as those caused by JPEG
compression, camera shake, or objects moving in the frame between
Tone mapping reduces the dynamic range of the entire image, but
keeps the localised contrast between neighbouring pixels - exploiting
features of the human visual system to create an image that represents
a wide dynamic range, but which can be reproduced on common LDR media
like an computer screen or photographic print.
Tone mapping is perhaps
more of an art than a science, and here HDR photographers love to
Many prefer a traditional look that maximises the detail in
a photograph while retaining realistic colour and contrast, but others
use tone mapping to create striking or surreal images that may look
distinctly different from the original scene - depending on their
taste, photographic style, and experience.
Learn More About HDR Photography
One of the best ways to learn about HDR photography is by watching a
HDR video tutorial. Trey Ratcliff from StuckInCustoms.com
is an expert
in HDR photography and has produced the best collection of videos on
this topic to date. Around 11 hours of lessons and instruction.
As part of his in-depth course you'll learn about creative and
post-processing techniques. You also get around 130 RAW images to
experiment with while watching the videos.