http://www.techradar.com/pro/linux December 2019 LXF257 71HDR photography TUTORIALS
around. However, F11 will force a full-screen display, so
we suggest you do that straight away. Using Luminance
HDR is pretty intuitive. Choose ‘New HDR Image’ and
then, in the HDR Creation Wizard, select the images you
want to combine. The images are loaded and an
estimate of the exposure appears for each. You can
correct these if needed. Click Next to go to the wizard’s
second screen. Unselect the Preview tickbox, which will
cause the Compute button to change to a Finish button,
which you should now click on. After some time, you’ll
be taken to the Tonemap window.
By the time the Tonemap window is displayed, the
HDR image will have already been generated, but there’s
a problem. In much the same way that a camera’s CCD
can’t record an HDR image, ordinary (non-HDR)
monitors can’t display them and printers can’t print
them. In that sense, creating a HDR photo is a pointless
exercise, or at least it would be without tone mapping.
Tone mapping aims to process an HDR image,
preserving as much as possible of the tonal range it
contains, while making it displayable on ordinary
hardware. Inevitably this causes some artefacts which
can range from subtle to extreme – although even the
latter can result in a visually attractive result, albeit not
altogether natural.
Now that’s clear, we can get back to the Tonemap
window. At the left are loads of options that control the
way in which the tone mapping operates. Next is a
preview of the currently selected options and, for those
who want a bit less choice, the small images at the right
represent various presets that you can select. We
suggest that you browse the presets first of all, and
then, if none of them really fit the bill, start playing with
the individual controls. Bear in mind, though, that with
15 different so-called operators (algorithms), most of
which have between one and five slider controls and afew of which have tickboxes,
you could be busy for quite
some time.
The tone mapping default
settings, as shown by the
thumbnails, tend not to include
the more surreal and garish
type of images that are often
thought of as HDR. Instead, to
varying degrees, most but not
all of them are moderately
realistic in appearance. What’s
more, playing with the controls
doesn’t produce really over-
the-top results. If you do crave
that ‘traditional’ HDR look, we
suggest that you select the
Mantiuk ’06 operator with the minimum Contrast
Factor and the maximum Saturation Factor. If that
doesn’t go far enough for you, there’s always the
option of importing the output of Luminance HDR into
GIMP for a bit of post-processing.
While using Luminance HDR to combine images you
won’t have burnt your bridges once you decide on a
tone mapping. The non-tone-mapped HDR image can
be saved as an HDR file format, of which Luminance
HDR supports several. This means that you can open
this HDR image in Luminance HDR later on and try out
alternative tone mappings. It also means, of course, that
you can share your HDR images with others, or carry
out the tone mapping using different software.
Our reference to HDR file formats brings us to the
subject of RAW files. As you might be aware, some
cameras save images in a format known as RAW, in
addition to more familiar ones like JPEG. As the name
suggests, this is the raw image directly from the
camera’s sensor, with no in-camera processing carried
out. Different manufacturers have different
specifications for their RAW formats, but typically they
store 12 or 14 bits per pixel per primary colour,
compared to 8 bits for a JPEG file.
That might not sound a huge difference, but each
additional bit doubles the number of tonal values that
can be represented. In other words, a RAW file has a
much larger dynamic range than a JPEG file and, in that
respect, it’s almost an HDR format. The reason for
mentioning this is that Luminance HDR can import RAW
files, and even if you only import a single one, you can
go on to tone-map it, producing a similar result to that
achievable with a few JPEG files.MAKE US LOOK BETTER! Subscribe now at http://bit.ly/LinuxFormat
None of the
exposures of this
cave entrance
come close to
representing the
full dynamic range
of the scene, but
combining them in
Luminance gives
an effective result.If tone mapping is pushed to the extreme, the end result might not
quite be realistic, but the end result can be quite eye-catching.6668Decmbr rb8c2019b21invst December 2019 LXF257 71
HDR photography TUTORIALS
around. However, F11 will force a full-screen display, so
we suggest you do that straight away. Using Luminance
HDR is pretty intuitive. Choose ‘New HDR Image’ and
then, in the HDR Creation Wizard, select the images you
want to combine. The images are loaded and an
estimate of the exposure appears for each. You can
correct these if needed. Click Next to go to the wizard’s
second screen. Unselect the Preview tickbox, which will
cause the Compute button to change to a Finish button,
which you should now click on. After some time, you’ll
be taken to the Tonemap window.
By the time the Tonemap window is displayed, the
HDR image will have already been generated, but there’s
a problem. In much the same way that a camera’s CCD
can’t record an HDR image, ordinary (non-HDR)
monitors can’t display them and printers can’t print
them. In that sense, creating a HDR photo is a pointless
exercise, or at least it would be without tone mapping.
Tone mapping aims to process an HDR image,
preserving as much as possible of the tonal range it
contains, while making it displayable on ordinary
hardware. Inevitably this causes some artefacts which
can range from subtle to extreme – although even the
latter can result in a visually attractive result, albeit not
altogether natural.
Now that’s clear, we can get back to the Tonemap
window. At the left are loads of options that control the
way in which the tone mapping operates. Next is a
preview of the currently selected options and, for those
who want a bit less choice, the small images at the right
represent various presets that you can select. We
suggest that you browse the presets first of all, and
then, if none of them really fit the bill, start playing with
the individual controls. Bear in mind, though, that with
15 different so-called operators (algorithms), most of
which have between one and five slider controls and a
few of which have tickboxes,
you could be busy for quite
some time.
The tone mapping default
settings, as shown by the
thumbnails, tend not to include
the more surreal and garish
type of images that are often
thought of as HDR. Instead, to
varying degrees, most but not
all of them are moderately
realistic in appearance. What’s
more, playing with the controls
doesn’t produce really over-
the-top results. If you do crave
that ‘traditional’ HDR look, we
suggest that you select the
Mantiuk ’06 operator with the minimum Contrast
Factor and the maximum Saturation Factor. If that
doesn’t go far enough for you, there’s always the
option of importing the output of Luminance HDR into
GIMP for a bit of post-processing.
While using Luminance HDR to combine images you
won’t have burnt your bridges once you decide on a
tone mapping. The non-tone-mapped HDR image can
be saved as an HDR file format, of which Luminance
HDR supports several. This means that you can open
this HDR image in Luminance HDR later on and try out
alternative tone mappings. It also means, of course, that
you can share your HDR images with others, or carry
out the tone mapping using different software.
Our reference to HDR file formats brings us to the
subject of RAW files. As you might be aware, some
cameras save images in a format known as RAW, in
addition to more familiar ones like JPEG. As the name
suggests, this is the raw image directly from the
camera’s sensor, with no in-camera processing carried
out. Different manufacturers have different
specifications for their RAW formats, but typically they
store 12 or 14 bits per pixel per primary colour,
compared to 8 bits for a JPEG file.
That might not sound a huge difference, but each
additional bit doubles the number of tonal values that
can be represented. In other words, a RAW file has a
much larger dynamic range than a JPEG file and, in that
respect, it’s almost an HDR format. The reason for
mentioning this is that Luminance HDR can import RAW
files, and even if you only import a single one, you can
go on to tone-map it, producing a similar result to that
achievable with a few JPEG files.MAKE US LOOK BETTER! Subscribe now at http://bit.ly/LinuxFormat
None of the
exposures of this
cave entrance
come close to
representing the
full dynamic range
of the scene, but
combining them in
Luminance gives
an effective result.If tone mapping is pushed to the extreme, the end result might not
quite be realistic, but the end result can be quite eye-catching.