High Dynamic Range
Adobe's Photoshop was the first program to introduce a high dynamic
range conversion way back in 2005 with CS2.
Since then High Dynamic Range images have been gaining more and more popularity and
some of the images are absolutely stunning.
The HDR conversion is really quite straightforward and after it is done
you
may find that the application of some additional Photoshop adjustments
is necessary.
This may include Levels, Curves, Hue and Saturation, Sharpening and
maybe even a bit of local Dodge and Burn with a Soft Light Layer - or
how about a black and white conversion or grayscale/duotone?
But first - Tone Mapping ...
Tone
Mapping
One of the things that I didn't understand about high dynamic range
conversions was tone mapping. It just didn't make any sense
to me so I did what any sane person with an internet connection would
do - I
typed Tone Mapping in the search bar and started reading the results.
What I found was a lot of bafflegab (at least it seemed that way to me)
but there were a few great nuggets of information.
If tone mapping is confusing to you as well then here are a couple of
definitions that may make some sense to you ...
- Tone mapping is a process that maps the colors in an
HDR image to a normal image which decreases the dynamic range to what
would be found in a normal image.
- Tone mapping compresses the tonal values of a high
dynamic range image into a lower one. The result is an image with more
visible details that would not be seen on an image with lower dynamic
range.
What this means is that much more of the details of the HDR image
become visible.
Toning an image will generally modify ...
- Glow.
- Tone and Detail.
- Color.
in interesting, unique and wild ways ...
High Dynmaic
Range Conversion - CS2 to CS4
Assuming you have three images that are one, two or three EV's apart
this is how to do the conversion ...
File >
Automate > Merge to HDR. When the screen
comes up click the Browse button to find the files you want to use or
drop down the menu and choose Open Files if they are already open in
Photoshop.
This is the screen that will appear with the names of the files in the
Window ...
At the bottom of the screen is a place to put a check mark in Attempt to Automatically Align
Source Images. If there is the potential that
some motion occurred when the images were taken then check the box.
When everything is set click OK.
It may take a few moments for the next screen to come up and it will
depend on the speed of your computer.
The next screen includes thumbnails of the original images on the left,
the resulting merge in the middle and a histogram with a slider to set
the white point preview.
Just above the histogram is the Bit Depth selector. It
defaults to 32 Bit/Channel and when the drop down is selected are two
additional selections for 16 Bits and 8 Bits.
When OK is selected without changing the Bit Depth you computer goes
through the processing and the high dynamic range image pops up on your
screen.
If either 16 Bit or 8 Bit is selected this is the screen that will
appear and you can make some adjustments ...
The important part of the dialogue is the Method drop down
menu. There are four choices in the menu ...
 Exposure
and Gamma - allows you to manually adjust the brightness
and contrast of the image with the sliders.
Highlight
Compression - this adjustment compresses the
highlight values in the HDR image so they fall within the luminance
values range of the 8- or 16-bits-per-channel image file. There are no
adjustments with this setting.
Equalize Histogram -Compresses
the dynamic range of the high dynamic rage image while trying to
preserve some contrast. There are no adjustments with this setting.
Local Adaptation
- Adjusts the
tonality of your high dynamic range image by adjusting the curve of the
image. This is the most useful adjustment of the bunch and
it's
very versatile.
Local Adaptation
When Local Adaptation is chosen the image will appear somewhat - well -
weird
but you have the ability to adjust the curves, the Radius and
the Threshold ...
Adjusting The Curve
The Curve for the high dynamic range image is adjusted like any curve
dialogue - place some points on the line and move them up and down or
left and right.
Comments about the curve ...
- This curve modifies only the luminance of the image -
there is no separate adjustment for the color channels. The
adjustments are applied to the whole image.
- The first adjustment will probably be to bring the
bottom of curve over
to the start of the histogram.
- A standard "S" curve will increase the contrast.
- Putting a checkmark in the Corner box (bottom
right) will smooth the transition between points on the curve.
- Holding down the ALT key while in this dialogue will
change the Cancel button to a Reset button if you need to go back to
the beginning.
- Oh - and make sure that Preview is checked
...
Working with the Curve in Local Adaptation will probably take a lot of
time so go slowly and make small adjustments.
Radius and Threshold
The Radius and Threshold adjustments will alter the degree of local contrast in
the high dynamic range image.
The Radius
controls the number of pixels that will be viewed as local.
A small number (like the default value of 16) will apply the
adjustment to very tight regions which will produce hard edged
enhancements in small regions. This will enhance detail.
The range of the radius is between 1 and 250 pixels. As
mentioned a low value will enhance detail while a high value will look
more natural but will lack details.
The way to approach this is to move the slider from one extreme to
another, keeping an eye on the image. Now slowly move the
slider until you find a setting you like.
The Threshold
sets the difference in luminance between adjacent pixels
for them to be included or excluded from the current local region and
the range is between 0.1 and 4.0.
When it is set too low then the image will be somewhat flat and setting
it too high will make local details stand out unnaturally.
The best way to figure this out is to actually try it - so - grab three
or more bracketed shots and run them through Merge to HDR in File > Automate,
select Local Adaptation and have some fun with the Curve and the
Radius/Threshold settings.
When you are satisfied click OK to complete the merge and then on to
post processing ...
Post Processing
Creating a High Dynamic Range image from some bracketed shots can
produce an amazing image but that is not the end of the story.
Like any image in Photoshop, the end result can be further modified
with the normal Photoshop tools, such as ...
- Curves
- Levels
- Hue and Saturation
- Additional Dodge and Burn (which is, by itslef, a
kind of High dynamic range conversion)
- Sharpening, and maybe some neat effects from the ...
- Filter Gallery
This was done with Photoshop CS2. The post processing was the
addition of a Curves Adjustment Layer and a Hue and Saturation
Adjustment Layer to bump up the colors.
The intent was to keep the HDR image as close to the original scene as possible.
For a more detailed look at Photoshop post processing of an HDR image - click here ...
High
Dynmaic
Range - CS5
Adobe has really stepped up with high dynamic range conversion in their
newest release
- CS5.
There are two High Dynamic Range modules in CS5 ...
- Merge
to HDR Pro in the File
> Automate menu,
and
- HDR
Toning in the Image
> Adjustments menu.
Merge To HDR Pro
The first module, Merge to HDR Pro is an upgrade of the one in the
previous versions of Photoshop and it includes a lot more adjustments
and some great pre-sets. It requires the typical bracketed
shots and works best with RAW images from your digital camera.
This may be Adobe's answer to the stand-alone HDR conversion
software packages that many digital editors believed did a better job
at HDR conversion than the previous versions of Photoshop.
HDR Toning
This one is great because you can do a high dynamic range conversion on
a single image.
Think about it - you have an old image that just isn't what it should
be - run it through Image
> Adjustments > HDR Toning and maybe the
hidden gem will reveal itself!
Merge to HDR Pro
The new High Dynamic Range conversion in Photoshop CS5 starts out
pretty much the same as previous versions. Simply go to File > Automate >
Merge to HDR Pro and either Browse to the images you want
to use or select the files open in Photoshop (Add Open Files).
This is the screen that will come up ...
The selected files are listed in the box ...
By default a checkbox is entered in the box at the bottom of the screen
- Attempt To
Automatically Align Source Images.
Click OK to
start the Merge process.
Depending on the speed of your computer you will be in for a short or
maybe somewhat longer wait for the next screen where all of the magic
will be happening.
This is where you will be doing all of the High Dynamic Range Toning
(the panel on the right side of the screen).
The image thumbnails and the resultant image are also visible.
There is a little Zoom slider at the bottom of the resultant
image screen if you want to zoom in closer.
Let's take a closer look at the Toning panel ...
Toning Panel
 From top to bottom ...
Presets
- Photoshop CS5 comes with a bunch of presets that you can apply (13 of
them), choose one, click
OK and you're done.
Remove Ghosts
- when checked it attempts to remove any ghosts caused by moving
objects.
Mode -
the panel defaults to 16 Bit with Local Adaption. The other
options are still there but Local Adaptation is the most useful by far.
Edge Glow
Radius - this slider controls the size of a Glow effect.
Strength - this slider controls the contrast of the Glow effect.
Tone and Detail
Gamma - adjusts the difference between highlights and shadows.
Exposure - the slider adjusts the overall image tone.
Detail - adjusts the amount of detail contrast.
Shadow - adjust the luminance of the shadow regions.
Highlights - adjusts the luminance of the the highlight regions.
Color
Vibrance - this slider adjusts the saturation while minimizing clipping.
Saturation - adjusts the color intensity.
That small, little, unobtrusive checkbox (Remove Ghosts) at the top of
the panel is really great. What it does is magically remove any ghosts
that occur as a result of camera movement or movement in the scene.
 |
 |
| Ghosts |
No Ghosts |
Would you just look at that - this feature is amazing - should'a been
called Ghost Busters ...
Back to Toning
Panel
Back to the Panel
If you've ever used the previous versions
of Merge to HDR in Photoshop
will quickly realize how much more useful this Toning Panel is than the
simple Local Adaption adjustments previously available.
At the bottom of the palette you can choose between Color and Curve.
Here are the two plaettes ...
 |
 |
| Color |
Curves |
With the Color panel you can adjust both the Vibrance and
Saturation of the image and with the curves dialogue you can do
anything that can be done with a normal curve dialogue.
All of
the adjustments you do on the image in the panel will be immediately
visible. This is a procedure that can take a lot of time to
complete so patience and a keen eye for what you want are required.
When everything is to your liking, click OK and Photoshop will process
the HDR image.
Post Processing
The high dynamic range image can be saved as is or further processed
with the normal Photoshop tools at your disposal -
- Curves.
- Levels.
- Sharpening.
- He and Saturation.
- Filter Gallery for some cool effects.
High
Dynamic Range On A Single Image
Photoshop
did something good - they added an HDR Toning adjustment for single
images. What this means is that you can dig through your old images -
the ones you love - and do an HDR Toning on it.
It is easy to do - just select Image
> Adjustments > HDR Toning and up will pop
the panel to tone your image.
The toning palette is similar to the one found in the Merge to HDR Pro
...
HDR Toning Panel
 |
Presets
- Photoshop CS5 comes with a bunch of presets that you can apply (13 of
them), click
OK and you're done.
Method
-
the panel defaults to Local Adaption. The other
options are still there but Local Adaptation is the most useful by far.
Edge Glow
Radius - this slider controls the size of a Glow effect.
Strength - this slider controls the contrast of the Glow effect.
Tone and
Detail
Gamma - adjusts the difference between highlights and shadows.
Exposure - the slider adjusts the overall image tone.
Detail - adjusts the amount of detail contrast.
Shadow - adjust the luminance of the shadow regions.
Highlight - adjusts the luminance of the the highlight regions.
Color
Vibrance - this slider adjusts the saturation while minimizing clipping.
Saturation - adjusts the color intensity. |
A good way to start with HDR Toning is to choose a pre-set and then go
from there. The thing about the conversion is that it's all
to your taste.
Here are a few single images that I converted ...
 |
 |
| City
Scape Original |
City
Scape Toned |
The toned image has more detail in the sky and more detail in the
shadow area - which is typical of an High Dynamic Range image.
 |
 |
| Leafy
Wall Original |
Leafy
Wall Toned |
Perhaps a bit too green but ...
 |
 |
| Tower
Original |
Tower
Toned |
OK - so I went a bit wild with this one but it does give the idea of
how powerful this HDR Toning adjustment really is - from mild to wild ...
 |
 |
| Sky
Original |
Sky
Toned |
The blue sky is better and there is some detail in the tall buildings
to the right.
 |
 |
| Building
Original |
Building
Toned |
I like the looks of the toned building but it sure is beyond what would
be considered "normal".
 |  | | Chess Club Original | Chess Club Toned |
HDR
Toning can even be applied to a difficult image like the chess club.
The default setting only needed a bit of tweaking to get it right.
If you've got CS5 then give this conversion a go - it does a great job.
If you have an earlier version of Photoshop and you have a lot of great
images that could use some tender lovin' care then maybe it's time to
upgrade to CS5.
|
