Alex Healing
Adastral Park Photography Club, 11th February 2010
HDR Photography
What is Dynamic Range?
For a scene: ratio between the brightest and darkest parts of the scene.
For a camera: ratio of saturation to noise. More specifically, ratio of the
intensity that just saturates the camera to the intensity that just lifts
the camera response one standard deviation above camera noise.
For a display: ratio between the maximum and minimum intensities
emitted from the screen.
The luminance of starlight is around 0.001 cd/m2, that of a sunlit scene
is around 100,000 cd/m2, which is hundred millions times higher
Source: http://www.hdrsoft.com/resources/dri.html
What is High-Dynamic Range
Photography?
 Post-processing technique where multiple
exposures are combined to create a single
image with higher dynamic range.
 They are 32-bit images (96-bits per colour pixel) with an
infinite set of values each pixel can take (floating point).
Standard RAW images are 12-bit and JPEG are 8-bit.
 In order to reproduce the dynamic range on low dynamic
range displays or prints, the ranges are compressed using by
tone mapping.
A ‘bit’ of conversion
12-bit
RAW
8-bit
12-bit
RAW
8-bit
12-bit
RAW
8-bit
RAW Conversion
(optional)
32-bit HDR
8-bit
HDR
Tone Mapping
(Dynamic Range
Compression)
Exposure Blending
Normal Exposure
(full-frame metering)
Exposure Bracketing
+1
0
-1
HDR Image
Not entirely new
 Gustave Le Gray, (1820–1884)
Source: http://en.wikipedia.org/wiki/Gustave_Le_Gray
Why HDR?
 “well… you really had to be there…”
 Film/CCDs are not eyes
 we are under a patchwork illusion all the time
(but ignorance is bliss)
 Realistic  Surreal
 Increases your photo-taking possibilities
 e.g. eliminate need for fill-in flash for
indoor/outdoor hybrid shots, direct sunlight, …
What you need
 A (digital) camera
 Preferably capable of auto exposure bracketing
 Ideally a tripod
 (I’ve never used one!)
 HDR software
 Some free, some commercial
 Lots of other optional tools
 Photoshop
 …
HDR Software
Source: http://wiki.panotools.org/HDR_Software_overview
Taking the photos
 Preferably use a tripod
 Use Automatic Exposure
Bracketing (AEB) where
possible
Source: http://www.usa.canon.com/dlc/controller?act=GetArticleAct&articleID=1646
 Shoot in either JPEG or
RAW. HDR software can
handle several RAW
formats.
Preparing the photos
 Be aware of any moving subjects
 can remove before to avoid ghosting or do in a
single step after the HDR image is created
 HDR software may be able to avoid ghosting but
there will always be cases where it fails
Combining the photos
 HDR software may have
integral image
alignment for handheld
photos.
 The combined image
will not display well on
your monitor however
until you tone map to
compress the 32-bit
image into something
renderable.
Tone mapping
 Depends what effect you want but if realism
is what you’re after then you have to be very
careful.
 Potential unwanted effects include halos, tone
reversals, noise and sometimes just too much
colour!
Tone mapping
Source: http://beforethecoffee.wordpress.com/photomatix-tutorial/
Surreal HDR
Photo by welshbaloney http://www.flickr.com/photos/welshbaloney/
Photo by aicizz http://www.flickr.com/photos/aicizz/
True Tone HDR (TTHDR)
Photos by ojaipatrick http://www.flickr.com/photos/ojaipatrick/
Some of my shots…
… and the reasons for why I shot them
Blown-out Skies
Silhouetted Foreground
Silhouetted Foreground
Nothing right
Outside from inside
Direct Sunlight
Direct Sunlight
Direct Sunlight
Direct Sunlight
Moving Targets
Moving Targets
Moving Targets
Moving Targets
Where are the colours?
Where are the colours?
A dull day?
A dull day?
Exposures and how many?
 Spot metering on the highlights and shadows,
note the exposure times.
 Multiply exposure time for highlights by four
successively (stop spacing of 2 EV) until you pass
the exposure time for the shadows.
 Three exposures with 2 EV is typically good but
you may have to go to full manual depending on
your camera model.
Remember your settings
 Settings should remain constant for all the
images in a series
 Focus
 Aperture (set small)
 ISO (set as low as possible, particular if using tripod)
 Auto white balancing (beware but impact minimised)
 Custom white balance or shoot in RAW
RAW  ‘HDR’
 Not strictly HDR but using a good RAW
converter you can create fake exposures which
sometimes squeeze more data out than you
would otherwise with a single image.
 Due to good noise reduction
 Dynamic range is essentially the same though as
you’re simply splitting the dynamic range of a
single RAW image (12-bits per colour) into slices
and then recombining.
HDR Panorama
 Panorama first, then HDR
 same effect across whole image
Post-post-processing
 Re introduce originals to make more realistic
and get rid of any ghosting.
 De-noising further.
 HDR software can be very powerful but there
may be times that you’d prefer touching up
further with what you’re familiar with.
HDR in conclusion
 Diverse: ultra-realistic to shockingly surreal
 Personal taste but think about what your aims are
 Don’t use for the sake of it
 If the scene lends itself to higher dynamic range,
otherwise many other post-processing techniques
that might be more suitable
 Go play, either casually or more seriously
 Doesn’t take long to get results and there is an
element of exploration and discovery in the tone
mapping process in particular
Thanks!
http://www.flickr.com/photos/alexhealing/tags/hdr/
http://www.hdrsoft.com/resources/