The Art of HDR Photography Part 4: HDR Workflow
Although all tone-mapping tools perform the same basic tasks,
- Lower global contrast
- Compensate the flattened look by adding local contrast,
they all produce very different looks. Why? It's all about the handling of what they consider to be 'local' and how they handle edges. All these tools use sophisticated algorithms to attempt to optimize how they deal with edges and how they define 'local' for adding contrast, but they all work differently and as such produce different results. There are no objective criteria to judge the results. It is often simply a matter of your personal preferences. This means that unfortunately we can't save you the work; you'll need to find the tools you like yourself: We just present the alternatives. All tools mentioned here have trial version, so you can experiment and test them with your own images.
We are also not going into detail about all the different parameters, as this can be found in the product manuals.
Tone-Mapping Tools we use
There are three ways to access Photoshop CS5's tone-mapping:
- During the Merge to HDR process. Read our comments why do not recommend this. If you are in a hurry you may save a few clicks though.
- Converting your image from 32 bit to 16 bit. This always involves a tone-mapping step.
3. Keeping the image in 32 bits and use Image->Adjustments->HDR Toning.
All these functions allow actually 4 different tone-mapping methods:
|CS5 tone-mapping operators|
For our purposes only two of them are really relevant.
Exposure and Gamma
We only use Exposure 0 and Gamma 1. This just reduces the bit depth without real tone-mapping.
This method is needed if you want to convert an image to 16 bits but you already did the tone-mapping using other methods (Photoshop HDR toning or with a 3rd party Tone-Mapping plugins).
In our opinion this is a quite complex dialog because many of the sliders interact with each other. Once you found some good settings you should save them as a new preset. The Local Adaptation options are beyond the scope of this article; if you want to know more you should check out Photoshop CS5's help files. Most of the time we prefer to use other HDR tools for tone-mapping.
Photomatix Pro is kind of the 'classic' HDR tool, and some think it produces a distinctive 'Photomatix Look', though these are images processed using Photomatix in a certain way. The Photomatix tone-mapping dialog seems quite complex at first because the settings also interact. Again it is advised to save settings as new presets. Once you start from presets the handling gets much easier. Photomatix's system of presets works very well.
Photomatix has many unique features, such as extensive batch processing and 360 degree panorama support.
There is also a Tone-mapping plugin for CS5 called Tone Mapping that works like Photomatix.
Unified Color HDR Express and Expose
We find the results from HDR Express very good (often looking what some would call “natural”). It is also the easiest to use tool we present. The more advanced tool HDR Expose will likely inherit some of the new features of Express.
At first glance HDR Expose seems complicated but once you understand the basics it is quite easy to use (read again our tone-mapping principles using HDR Expose in the Dynamic Range chapter.
Unified Color also produces a CS5 plugin “Float 32” that has about the same features as HDR Expose.
Nik Software HDR Efex Pro
|HDR Efex Pro|
We use HDR Efex Pro mainly as a CS5 plugin. HDR Efex Pro has more options than any other HDR tools, which makes it very powerful but also complex. We use it mainly to create a specific 'look' for our images, and for this we love HDR Efex Pro (see later in this chapter). The preset system in HDR Efex Pro makes this tool more accessible and our advice would be that you explore all the presets first.
Because Photoshop CS5 allows you to perform multiple different tone-mapping operations on the same HDR image (using the same or even different HDR tools) it is possible to organize these results as layers and blend the results using masks. For our work we only experimented with this option but is can be very useful at times.
Adding a “HDR Look”
Images like this one are often called to have the HDR or Grunge look :
The interesting point is that the above photo is not a HDR photo; some would call it a 'single photo HDR'. Why is this look associated with HDR? Many HDR photos shown on the web have the following properties:
- High Saturation
- Strong local contrast
This look polarizes people. Some love it, and some hate it (calling it 'over-cooked'). We have no firm opinion, as we think it sometimes works for our taste and sometimes it does not. One thing is for sure HDR would be far less popular without this look. All HDR tools can produce such a look from real HDR photos or single shots. The most choices offers Nik Software’s HDR Efex Pro.
As a consequence we actually split the process into two parts:
- Creating a kind of “normal/natural” looking tone-mapped HDR photo
- Adding a look later (also used for single exposures like in our example above)
In our sample image the look works very well to emphasize the gritty look of rusty and old objects. Grunging a Ferrari may not look that interesting unless you were using it in a more humorous way. It always depends on your vision
Here is another example.
We think this image looks nice and would not need any improvements. We still created a different look in HDR Efex Pro.
|Added 'HDR' Look|
Does it look better? That's simply not the point. It looks different because we created a different mood. The first version shows the realistic beauty of the plane and the second version looks more like from a fairy-tale.
Here is our first ever “Grunge” photo and still one we like the most.
This is from a real HDR sequence and at its core was created by double tone-mapping in Photomatix Pro. Is it over-cooked? You bet, but that is the whole point. Realistic representation was not our goal (during the editing process we also added some Texture Blending to it).
Post Processing of HDR Images
We hardly ever consider the editing work finished once we have performed the tone-mapping. We just mention the next editing steps without going into the details because these are general editing techniques (the general workflow is covered here). We always work in Photoshop for the final optimization step.
- Crop & Straighten
- Perspective Corrections
- Cloning, Healing and Content-Aware Fill (in Photoshop CS5)
- Global tonal corrections
- Global color tuning
- Selective tonal and color corrections
- Adding a look (see previous section)
This is an edited version of the first chapter of an ongoing work by Uwe Steinmueller of Digital Outback Photo, featuring his personal experiences of HDR photography, and will eventually form the basis of a book on the art of HDR photography. If you'd like to find out more about digital imaging workflow from a fine art photographer's perspective then check out the Digital Outback Photo E-book, 'The Digital Photography Workflow Handbook (2010)', by Uwe Steinmueller and Juergen Gulbins, which covers the complete digital photography workflow from input to output. The 540 page prize-winning handbook covers everything from Import to Print (and even backup) and also features Photoshop and Lightroom techniques, HDR, color management and raw editing.
Also check out our Photoshop processing scripts here.
© 2010, www.dpreview.com & Uwe Steinmueller.