Photogrammetric Camera Exposure makes the targets easier to find and measure

For photogrammetry purposes, it is desirable to set the targets bright and the background dim. When retro-reflective targeting is used, the target and background exposures are almost completely independent of each other. The target exposure of Photogrammetric Camera is completely determined by the flash power while the background exposure is determined by the ambient illumination. The amount of background exposure is controlled by the shutter time. Eliminating the background exposure makes the targets easier to find and measure. However, if there is no background image whatsoever, trying to figure out which target for photogrammetry is which can be difficult. Usually, a compromise is reached and the background exposure is set so the object is dim enough to not interfere with target measurement, but still bright enough that it can be seen when enhanced.

Background Exposure of Photogrammetric Camera
The shutter time is used to control the background exposure. When the Photogrammetric Camera is off-line, the shutter time is selected using the mode switches that are located on the top of the camera next to the display. The available shutter times on an INCA2 range from 8 milliseconds to 8 seconds.

The INCA2 Photogrammetric Camera has an AUTO Exposure feature that can be used to automatically set the shutter speed. The default setting is to use the AUTO Exposure. If AUTO Exposure is selected, the shutter exposure is set automatically the first time you take a picture on a job.

Target Exposure Photogrammetric Camera

The flash power setting for the target exposure depends on the distance from the Photogrammetric Camera to the targets, and the target size. The following diagram gives recommended flash power settings at varying distances. If you are shooting the object in sections, use the size of the sections. The tables assume the recommended target size (which is also listed) is used. If the targets are smaller than this, you may want to increase the flash power setting one step to help compensate. The tables assume the default lens f-number of F11 is used with an INCA. It is important to check the lens and make sure it is set to f11, the default setting for the lens.