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Workflow
The following figure provides a view over the principal FDRTools workflow.
It shows the essential participating modules within the functional groups.
The diagram shows the status quo of planning and realisation.
Modules colored in green are implemented, yellow modules are currently under construction and red modules are not yet implemented.
Registration
Merging several, differently exposed images implicates a couple of problems.
One of these problems which arises already when taking the images is the movement of the camera itself.
If the camera jiggles then the exposures won't fit exactly together.
Instead they are slightly displaced yielding an unpleasant blurry look of the combined image.
Camera movement is nearly unavoidable.
Only mounting the camera to a tripod and using an accurate shooting technique can avoid jiggling in most cases.
Tripod
This is a method for registering of photos that were taken using a tripod.
It allows to compensate for slight vibrations of the camera.
Hand-held
Combining photos taken freehand requires more elaborated correction measures.
In principal all possible degrees of freedom of a camera must be taken into consideration, i.e. all movements of the camera during the image taking session must be reconstructed from the photos.
Methodically this happens via the recognition and localisation of identical features among the photos.
This information then allows to translate, rotate and zoom the images accordingly.
HDRI Creation
Normally each image of an exposure series has a different exposure.
Hence the images have different brightness.
These differences must be calculated and each pixel of the resulting HDR image must be optimally exposed.
Overexposure and noise must be avoided.
Moving objects like persons, cars and plants moved by the wind pose a serious problem when combining several temporally successive photos.
Average
This is an optimal method for creating an HDR image from several, differently exposed images of a static scene.
There should not be any moving objects in the scene.
Separation
This method allows to separate a scene into several intensity areas.
The resulting HDR pixels of such an area are taken exactly from one source image.
Thus it is possible to treat moving objects proper and avoid blur or ghost objects in many cases.
Creative
Creative allows to blend images with differing content.
You can combine images with different exposure, aperture or focus settings or combinations of these, images taken under different lighting conditions like dusk and dawn photos, flashed images or even images with totally different content.
Creative works similiar to layer composition in Photoshop or GIMP but without the limited intensity range (8 or 16 bits per channel).
Hence Creative is categorised as HDR creation method.
Tone Mapping
A (well done) HDR image should only have well exposed pixels, i.e. there should not be any overexposed or noisy pixels.
However, an HDR image can't be displayed properly on common media like monitors or photographic prints.
It is therefore necessary to compress the dynamic range of such an HDR image.
FDRTools provides you with three differing methods to accomplish this tone mapping process.
Simplex
This is a simple yet fast method that is used to get an overview of the HDR image.
A disadvantage is that it yields poor image contrast.
Receptor
This method uses one of the best global algorithms currently availabe for the purpose of tonal range compression.
Global means that the same formula is applied to all the pixels of an image.
Compressor
This method acts locally.
That means: the algorithm investigates the surrounding of a pixel and from this information calculates an optimal compression value.
This method is computational expensive but delivers quite contrasty and natural acting results.
End.
Do you have questions or suggestions?
If so you may want to publish them in the Forum.
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| FDRTools 2.2 released |
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| 18 Aug 2008 |
| Version 2.2 extends HDRI creation possibilities, improves usability of HDRI creation and tone mapping functionality and fixes several minor problems of the previous version. [read more] |
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| FDRTools 2.2beta3 released |
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| 08 Aug 2008 |
| Version 2.2 extends HDRI creation possibilities, improves usability of HDRI creation and tone mapping functionality and fixes several minor problems of the previous version. [read more] |
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| FDRTools 2.2beta2 released |
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| 04 Jun 2008 |
| Version 2.2 extends HDRI creation possibilities, improves usability of HDRI creation and tone mapping functionality and fixes several minor problems of the previous version. [read more] |
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