HDR Photography using Photomatix Pro -
by Honez
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Okay, so here's the thing; here I am, happily tinkering
in Photomatix,
when I get an email from Geoff. "Hey honez,"
he says, "you've really been getting into HDR,
how about you write something about your experiences?
It might be fun and kind of interesting to see how
you're getting on." So that's it, my dilemma,
how does a complete HDR noob like me write something
interesting and informative? Well I'm really not sure,
but this tutorial, among other things, shows how I
turned this pretty ordinary photo of a Traction Engine
(left), into what I hope you'll agree is a much better
HDR image (right).
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| First off, an example; imagine a mountain
landscape. It has a nice log cabin in the foreground,
flanked by a rugged mountain background, all topped
off with a nice fluffy cloud. If I was to whip out my
camera to take a photograph, right away I'd have to
make some compromises. What's the main subject of the
scene? Do I expose to reveal the detail of the cabin?
If I do, I'm going to lose the subtleties of that lovely
cloud. If I compensate for that, the cabin will look
dark and uninviting. I could split the difference and
expose for the mountain, but then both the cabin and
cloud won't be quite right. And worst of all, none of
the shots are going to look like it does right now,
to my eyes everything is just peachy as it is, I can
see the detail in the cabin shadows and highlights,
and in the craggy mountains, and in the cumulus nimbus,
all proud and puffed up, looking down on me fiddling
with my camera settings. |
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This is what HDR, High Dynamic Range imaging, is
all about. It combines the dynamic range of multiple
exposures into one image. Detail normally lost in
shadows or washed out in overexposed areas are captured
and revealed, better matching what we see with our
own eyes. Well, that's the theory at least. Like any
process that manipulates digital images, it's subject
to interpretation and the whim of the person doing
the driving. Some of the things you can do; boosting
local contrast, shadow and highlight details, saturation
levels, etc, can make the image look too surreal,
and images can end up looking like a scene out of
Mary Poppins on acid if you're not careful.
The software I use to produce HDR images is the OS
X version of Photomatix
Pro and Photoshop Elements. I know there are others
out in the marketplace, and more “professional”
versions of Photoshop can pretty much do all of this
out of the box, but I'm going to describe what I do
using the software that I'm familiar with. |
Step 1
The first thing you need to do to produce an HDR
image is, strangely enough, take some images that
you're going to convert. Usually, this will be three
differently exposed photos of the same thing, so some
kind of still life, architecture, landscape or other
non-moving subject is the best. Anything with clouds
or shiny metallic elements usually come out looking
really good, but anything with a large dynamic range
should come up nice. It is possible to produce HDR
images from a single RAW exposure, manipulated and
saved three times at EV 0, -2 and +2, but these never
look as good as three exposures done correctly.
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The easiest way to get three images to process is
to use a tripod, set your camera to 'Aperture Priority'
and use 'Auto Exposure Bracketing' (AEB) mode. I've
found that setting AEB to be 0, -2 & +2 gives the
best results, but technically it should cover as much
of the dynamic range in the scene as possible. If your
camera supports AEB of more than three exposures and
has a greater F-stop range, then go for it. If you don't
have a remote shutter-release, then I'd recommend using
the self-timer function, and mirror-lockup if possible,
to avoid any vibration and potential misalignment of
the shots. Another tip I've picked up on is to expose
for the shadows in the scene, overexpose rather than
underexpose, which generally gives a better final result.
Also, select as low an ISO setting as you can, which
is ISO 100 on my camera. Any noise in the source images
will be amplified by the HDR merging process, so it's
a good idea to start with as clean an image as you can. |
Step 2
Now you should have three or more images to post-process.
I've found that source RAW images work better than
JPEG. I won't bore you with the details, but JPEGs,
by their nature, have already lost some of the dynamic
range you're trying to bring out, so go for RAW if
possible.
This part of the process is optional, but I've found
that the overall quality of the final result is better
if I pre-process the RAW images before I use them.
I open each of them up with the Photoshop Elements
RAW editor and set all of the correction sliders to
zero. I save the image as 8-bits per channel and use
those as input to the HDR process. By zeroing the
corrections, you can be sure each of the images differ
only in their exposure values, which is exactly what
you need for HDR processing. |
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 Step
3
Now I just drag the files, saved in Photoshop Elements
as digital negatives (.dng), across into Photomatix
Pro. Depending on the effect I'm after, I'll either
generate it as an HDR image, or blend the exposures
of multiple images. Exposure blending gives a very
natural, photographic, end result and has the benefit
of only minimal increase in overall noise. But the
“Generate an HDR image” option usually
gives a more visually pleasing result, which is what
I'm going to select for my traction engine.
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 Because
I dragged and dropped the image files, the file names
are pre-populated onto the source image screen, so
I just hit OK.
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You can get a 15% discount on Photomatix
Pro software. Just put 'GeoffLawrence' (without
the quotes) into the coupon box when you make
your purchase. There is also a free
trial version that you can download on
their website. |
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