Calculate calibration parameters

Calibration-Set Manager
Residue distortion
Interpretation of residual distortion
Calibration-Set Manager features
Create new / edit Calibration Set

Calibration-Set Manager

Clicking on the button "Calibration Set Manager" on the main form or alternatively on File >> Calibration Set Manager opens following window:

Calibration Set Manager

The Calibration Set Manager manages the Calibration Sets of the different cameras respectively camera-lens-combinations. If an entry is selected, apart from the camera and lens designation also the corresponding distortion values are displayed, which give information about the distortion extend before and after calibration parameter application.

Because these values are not reliable with downloaded Calibration-Sets, they are displayed in gray in this case.

Distortion in the source image: Average and maximal distortion of the distorted, original images in pixel respectively IIU
Distortion with LQ calibration: Average and maximal residual distortion in pixel respectively IIU of the images processed in LQ mode
Distortion with HQ calibration: Average and maximal residual distortion in pixel respectively IIU of the images processed in HQ mode

Residue distortion

By re-application of the produced calibration parameters to the point positions, which were determined from the Calibration-Pictures, a parameter accuracy estimation can be made. Accordingly the residue distortion information only applies to corrections in the captured focal lengths. Thus no statement can be made about the residue distortion for interpolated focal lengths.

The residue distortion reliability for the HQ-mode is quite high, since a variable safety factor was added here. The residue distortion is indicated higher, if for instance only one Calibration-Picture has been evaluated for the appropriate focal length. If on the other hand multiple Calibration-Picture are used, on which slightly different views of the Calibration-Map are visible, the residue distortion approximates to a smaller value.

In the LQ mode however no safety factor is added. The indicated value is a minimum value and therefore the real residue distortion is somewhat larger in all probability.


Interpretation of residual distortion

Using the high quality Calibration-Map usually the average residual distortion after HQ-mode calibration approximately amounts 0.1 pixels and the maximum residual distortion approximately amounts 0.5 pixels (with a camera with a resolution of approximately 4 megapixels).

If a lower quality Calibration-Map is used, where the points are not arranged accurately for example due to a lack of flatness, the residue distortion is accordingly higher in the HQ-mode, since ImageIron presupposes an optimal and thus plausible point arrangement on the Calibration-Map.

In contrast to the HQ-mode, in the LQ-mode neither the radial asymmetrical, nor the tangential distortion is removed. Assumed, the used camera would contain lenses, which have an ideal, to the optical axis symmetrical, surface, and assumed, these lenses and the optical chip would be ideally aligned, then the residue distortions would be equal in HQ- and LQ-mode. Since cameras and lenses in actuality show manufacturing inaccuracies however, the residue distortion values of HQ- and LQ-calibration differ from each other. The higher the residue distortion is in the LQ mode in contrast to the HQ mode, the more inaccurately the lens respectively the camera has been manufactured.


Calibration-Set Manager features

Edit: Allows to rebuild the selected Calibration Set or change the user postfix. See below for further information.
New: Create a new Calibration-Set. See below for further information.
Save: Save the selected Calibration-Set as single file in any folder.
Remark: Each time ImageIron exits, the existing Calibration Sets are stored internally and thus are automatically available with the next start. The function "Save" enables to create a backup or to transfer a Calibration Set to another ImageIron installation.
Load: Import a Calibration Set from a file (analogue to "Save").
Delete: Delete a Calibration Set.
Upload: Upload the selected Calibration Sets to the NaturalGrafiX server. Uploading the self-created Calibration Sets supports further development of the product.
The data is sent anonymously (as long a the user postfix does not contain an identification).
Download: Allows to search and download prepared Calibration-Sets from the server-database.
Analyse: Offers analysis and export functions for the calibration parameters. Read this for further information.

Create new / edit Calibration Set

Create new / edit Calibration Set

The Calibration-Pictures form the basis for the calibration parameter calculation. Use the button Add Calibration-Pictures ... to add them to the list in the currently opened tab. If particular pictures shall be removed, select them in the list and click Remove selected Calibration-Pictures.

If the Calibration-Set shall not be created for a shift-lens, it is only allowed to append the list under the tab Shift = 0.

In order to reach a satisfying Calibration-Set build result, it is required that the Calibration-Pictures are not preprocessed and are available in (original) landscape format.

The calculation is started with Calculate calibration parameters.

Before the form is closed with OK, the new Calibration Set can be named with a user postfix (upper text box), in order to enable unique identification.

The Calibration-Sets will be available on the next application start and just need to be exported with Save for backup purposes. The data is filed in the userīs application-data folder.

It is recommended to keep the used Calibration-Pictures since ImageIron probably will be upgraded with further correcting functions, for which the Calibration-Pictures are probably required again.

Continue with "Calibrate digital photographs"