The Camera Viewer Dialog displays a Camera's parameters. It can be used to modify a Camera or to define new approximate camera parameters. The parameters need to be set to reasonable default values before calibration or when building an Approximate Camera.
The following list describes each of the parameters:
|
Parameter |
Description |
|
Name |
Provide a name for the camera to help you identify it. The name is used when storing the camera to the camera library so do not include characters such as “:” or “\”. |
|
Calibration Type |
The type of calibration. This will show either “Full”, “Field”, “Self”, “Exif Estimate”, “SmartMatch auto-calib”, “Inverse Estimate”, “Idealized”, “pre-V6” or “None”, depending on the type of project and processing used to ‘solve’ the camera. |
|
Focal Length: |
The focal length (in mm) of the lens of the camera being calibrated. A PhotoModeler Camera can have only one focal length. Set this to the figure printed on the lens or in the camera specification sheet. See note below regarding macro lenses. |
|
Format Size: |
The size of the imaging area in millimeters. For example, 35mm cameras have format size of approx. 36x24mm. This is not the print size. See the section "Determining Digital and Video Camera Format Size" for a quick way of determining format size. |
|
Principal Point: |
The reference point in the image to which all marks and lens distortion parameters are related (in mm). In a CCD camera the principal point is relative to the upper-left corner of the image. In a perfect camera the principal point is in the middle of the image (half the format size). |
|
Lens Distortion: |
Parameters that describe two non-linear functions of radial and decentering lens distortion. These can be set to zero for approximations. Also see Lens Distortion Formulation. |
|
Calibration Quality Values: |
If the camera was calibrated in Version 6 or later, a few ‘quality’ indicators are stored with the camera and displayed here. These include “Overall Residual RMS” (in pixels), “Maximum Residual” (in pixels), and “Photo Coverage”. See Quality Review Points-Based for more information on these quality indicators. |
|
Used by Photos: |
The photos to which this camera has been assigned, listed by photo number. |
|
Image Size: |
The resolution of the images created by this camera, and size in MP. |
|
EXIF fields: |
When a camera is created, EXIF information is extracted from its images and stored with the camera. EXIF information is used when matching photos with cameras in the library (see Camera Matching). These fields list the camera Make, Model, Focal Length, and Format Size as obtained from the information stored in the image’s EXIF header. If a photo does not contain EXIF information, “n/a” is shown in these fields.
To reset a camera back to its default EXIF Camera parameters (e.g. its state before any solved calibration), press the Reset Camera to EXIF Values button. This will clear all lens distortion parameters and other parameters depending on the contents of the EXIF header. Camera will be stored once you press OK. |
Note 1: If your camera has a macro lens you should be aware that the focal length can change a lot as the focus changes. All lenses change their principal distance (what we call focal length above) a bit as they focus but it can be extreme in a macro lens. For example, a Nikon 50mm macro lens could become a 100mm lens if focused at only a few inches. It is the 100mm value you need to enter in the dialog.
Note 2: Lens distortion values are shown in scientific notation. This notation makes it easier to compare small values. The last three digits are the power of 10. For example, 2.34e-004 is the same as 2.34 x 10^-4 or 2.34 x 0.0001 = 0.000234. So 1.2e-006 is a smaller number than 3.4e-005. Positive numbers can be used in the exponent too but you will not see that with lens distortion parameters (1.53e+005=153,000).