Expanding the tonal range of an image is the overall goal
of HDR (High
When you see the prints of Ansel Adams and Fred Archer,
you begin to understand the impact that HDR has on digital imaging.
They were able to capture and render images on analogue film of scenes
that spanned an extremely wide EV (exposure value) range. Understanding
and applying the Zone System in Film Imaging is analogous to applying
HDR in Digital Imaging.
Before going any further
in this tutorial, you need to do
two basic things.
For a detailed answer to these questions and for a list of website
addresses discussing opposite thoughts about recording images with a
wide dynamic range go to the main HDR page.
- you should make certain that you understand what an HDR
- you should know the basic steps in using your camera to
record the series of images necessary for HDR.
In brief, the tonal range of
- Print paper is 8EV
- An LCD screen is 8EV
- Analogue film is 10EV
- An digital sensor in an average amateur camera is 12EV
- An analogue light meter (like Sangamo Weston) is 14EV
- A top digital sensor is 14EV
- The range of a sunset is 16EV
- An digital sensor in a top professional camera is 19EV
So the main aim is to squeeze the full tonal range of the subject into
an image with a narrower range.
In the "old days" of film the words of wisdom from the wizened
photographer were, "Expose for the shadows, and develop for the
That's a good maxim for digital users too, since
you can always pull some detail from the shadows, but you can’t rescue
anything from blown or burnt out highlights. Hence, HDR has a use.
The first image was taken "on the hoof" and was not planned as
HDR. The car was 30 minutes away, and the tripod an additional 25
km by gravel roads. I exposed for the outside of the cave, and
then carefully without much movement for the cave interior.
Paint Shop Pro HDR With A Slight Misalignment
The algorithms in the HDR routine look for contrast changes at
The inside of the cave has no details in the shadows for
the image exposed correctly for the cave exterior, so there's a big
contrast change at the cave mouth.
The outside of the cave has
little detail in the highlights for the image exposed correctly for the
cave interior, so again there's a big contrast change at the cave
This gives the range for HDR, and providing the alignment
is close, they should match up.
second at f22
second at f6.3
The two images were not taken with HDR in mind, so the main "rules of
HDR" were broken.
On the first attempt the mismatch can be seen, but using <align
images>, alignment occurs.
If you try this with multiple images which "break the HDR rules" you’ll
find the software will NOT cope.
Setting the brightness and local tone mapping values produces a pretty
An adjustment in the image tonal range is all that is required to
complete the job.
Setting The Parameters
So if Paint Shop Pro works by following edges and tone range boundaries
can I emulate this and set my own parameters?
Sharply defined edges lend themselves well to masking in Paint Shop Pro.
Working on the darker of the two images, the edge of the cave mouth was
traced using the magic wand; the Wacom graphics tablet is really the
option for fine control. The darker cave section was chosen and
selected to make a mask.
Layers > New Mask Layer >
At this stage the mask can be edited and fine tuned by painting on the
mask layer with white to expose the layer underneath and black to hide
Since we know that there is a slight mismatch in the alignment of the
images using the pick tool this misalignment can be adjusted as the
position of the base layer can be moved during the process of assembly.
The brighter of the two images is copied and pasted under the darker
one with its mask, and again the Wacom graphics pen is the ideal tool
it into position with fine control
The advantages, here, are that the individual layers can be adjusted or
manipulated using all of the adjustment tools, and the layer mask
tweaked to suit the demands of the user. The fine use of the
Wacom tablet pen gives a control not possible in the algorithms in
the HDR routine.
Another Way Of Merging
And onto another image and way of merging
The second series of images was specifically taken with HDR in
The second series of images was specifically taken with HDR in mind.
Richard and I had been having a debate about HDR for several
months. Then, subsequently, I was reading a book on Night
Photography which contained a detailed chapter on the use of HDR in
recording images at night, it seemed the right time to test the
theories out for real, and push them to the limit especially with Paint
Shop Pro in mind.
The range of all of the exposures that evening was over 7 stops, but
applying the parameters, a 5 stop range met the project brief.
|80 Seconds at f11
|40 Seconds at f11
|20 Seconds at f11
|10 Seconds at f11
|4 Seconds at f11
Load the images into Paint Shop Pro’s HDR editor File > HDR Photo
Paint Shop Pro’s HDR algorithm was allowed to do its best and a pretty
fine job it does too.
Can masking give a similar
I’ve never been over talented with the masking brushes on fine
images. The cave mouth had a coarse edge, and when I tried to
manually cut a mask on this second image I failed miserably.
my next question was how can I cut a mask without using a brush, but
leave myself the option of using the fine use of the Wacom
pen to tidy up at the end and tweak the image?
The middle exposed image, and the two end images were chosen since they
gave detail in the highlights; detail in the shadows and opportunity to
adjust some of the highlight areas.
Load the first image into Paint Shop Pro. To generate each mask
for each layer you must have each image opened separately.
Adjust > Brightness and
Contrast > Threshold sets pixel below a
chosen value to be black; and every pixel above the value to be
white. The value 180 seems to be a good value at which to start.
Make the mask. Layers > New
Mask Layer>From Image
Save the mask into a file to be used later. Layers > Load/Save
Mask > Save Mask to Disk. It’s a good idea to choose
that are meaningful. Mine were, eg. 180pic14 which meant picture
14 with threshold set to 180.
Do that for each image.
Clear all images of the Paint Shop Pro work area and re-load the three
images you’re going to use for the composite.
Choose the brightest image for the background, the mid-image for the
middle layer and the darkest image at the top of the stack.
- Select the middle image Edit>
- Select the brightest image Edit
> Paste as New layer
- Select the darkest image Edit
- Select the brightest image Edit
> Paste as New layer
Select the top layer in the layers palette. Reload the mask made
from this layer.
Layers > Load/Save Mask >
Load Mask from Disk ...
Do this for the middle layer in similar fashion
And there you have it. More importantly, each of the layer masks
can be edited; and you can use a different threshold value to make a
different mask to experiment to improve on your result
Paint Shop HDR
A Third Way To Merge