Creating a High Dynamic Range image
Introduction
A High Dynamic Range (HDR) image represents the whole range of values of light reflected by a scene, from its deepest shadows to brightest hightlights. In order to store the range of values with sufficient precision, HDR images are stored in floating-point representation, which is why they are referred to as 32-bit images (32 bits/channel) as the floating point type is encoded with 32 bits in computing.
The dynamic range of real-world scenes is often much higher than the dynamic range digital cameras can capture. For this reason, a single photograph, regardless of whether it is a RAW or jpeg file, is considered Low Dynamic Range as the camera sensors can only capture partially the dynamic range of a scene. The part of the range captured depends on the exposure setting. Capturing the dynamic range in its totality therefore requires that you take multiple exposures.
So, in order to create an HDR image, you will first need to take several exposures of the scene. Then, Photomatix will combine the photos to create a 32-bit HDR image from them. The number of photos needed depends on the dynamic range of the scene as well as the EV spacing separating each exposure.
For more information on how to shoot a High Dynamic Range scene, see the section Taking differently exposed images.
To create an HDR image from differently exposed photos:

1.
Drag your bracketed images to the open Photomatix Pro application (Windows) or to the Photomatix icon in the Dock (Macintosh). Alternatively, you can also click on the "Generate HDR Image" button of the Workflow Shortcuts, or choose Process > Generate HDR.
2.
If you have not dragged and dropped your images, click on the Browse button to go to the location of your bracketed images and select them using the SHIFT+Arrow keys or your mouse and CTRL key (command key on Mac).
3.
Check the OK button of the "Selecting source images" dialog.
The calculation of the HDR image requires the exposure value of each input image. If the exposure information cannot be found in the Exif data, Photomatix will show a dialog where you can input the Exposure Values for each one of your images (see note below). This dialog will also show if two or more source images have the same exposure setting. The Exposure Values need to be entered as relative values (i.e. values of -2, 0, +2 are the same as 0, +2, +4 for instance). A doubling of the exposure time relates to an increment of 1 in the Exposure Value, provided that the aperture and ISO settings did not change.
Generate HDR options
Alignment settings
The Align source images option corrects misalignment problems when the camera moves slightly between the bracketed frames. This always happens with hand-held photographs, but may even happen when shooting with the aid of a tripod.
There are two alignment methods. The first one, By correcting horizontal and vertical shifts, is fast but corrects for translation movements only. The second one, By matching features, corrects for both rotation and translation, and is recommended for hand-held shots. Given that each method is based on a different algorithm, try the other one when one fails.
The Don't crop option is useful when the resulting images must have the same width and height as the source images.
Chromatic aberrations reduction
This option attempts to automatically correct color fringing due to chromatic aberrations of the lens. Checking this option is recommended, given that chromatic aberrations tend to show around high contrast edges, and are thus particularly an issue for HDR images.
Noise reduction
This option reduces chromatic noise and, to a lesser extent, luminance noise. This option is recommended when you are processing RAW files directly in Photomatix.
Note that the noise reduction is done on the HDR image itself once it has been created. This means that you don't have to check the noise reduction option on the dialog for generating the HDR image when you need noise reduction. You can apply noise reduction to your HDR image later on by choosing Utilities > Reduce Noise.
Ghosting reduction settings
Ghosting artifacts appear when combining images of a dynamic scene. Photomatix Pro offers options to reduce two types of ghosting artifacts. The option Background movements reduces ghosting artifacts caused by background elements that follow a rhythmic pattern (flowing water, for instance), oscillating between shadows and highlights. The Moving objects/people option attempts to reduce the 'ghosts' in the combined image due to moving persons, animals or objects.
It is important to note that selecting Moving objects/people lowers the quality of the resulting HDR image. Only select this option if it is really necessary, and try first with Detection set to 'Normal'.
Tone curve options
The recommended option, Take tone curve of color profile, is selected by default. This is usually the best choice when the image files come from a DSLR camera or have been converted from RAW files. This option loads the Tone Reproduction Curve data from the ICC color profile associated with the source images in order to determine the non-linear function applied to the raw sensorŐs data. If no profile is available, it uses the tone reproduction curve of the Adobe RGB color profile.
When the images are scanned films or taken with a compact camera, it may be worthwhile to check the option Attempt to reverse-engineer tone curve applied.
If your source images are 16-bit TIFF files that have been converted from RAW files with a RAW converter that allow the image to be left in linear space (note: very few RAW converters allow this), then check the option No tone curve applied - pixel values are linear. Only check this option if you are 100% sure that the tonal values of the images are linear relative to the values of light captured. Please note that the term "linear" may have a different meaning depending on the RAW converter. In Adobe Camera Raw, for instance, linear is relative to the Adobe RGB color space and not to the values of light, so you should never check this option with files converted with Photoshop or Lightroom.

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