Historical Aerial Photography

[Matt]

Hi,

I am currently running a research project looking at a time series of historical photography starting in the 1940's. The photos are 1500 dpi scans from the original film and I have managed to get some small mosaics happening with very low settings and by masking out the borders and fiducial marks. I have noticed however that the derived camera calibration information differs for each photo in the series. In theory this calibration information should be identical for each photo do you have any suggestions as to why this would be the case, and for gaining the most accurate results using this process.

Many Thanks

Matt

[Dmitry Semyonov]

Hello Matt,

PhotoScan maintains equal calibration for photos in the following cases:

• Photos have the same size and equal EXIF focal length values
• Photos have the same size and unspecified EXIF focal length
• Photos are calibrated manually and manual calibration parameters are the same

It seems that you are using uncalibrated photos of different sizes. In this case, you can either crop the photos to the same size, or calibrate them manually using "Camera Calibration..." command from the "Tools" menu.

For best accuracy it is also recommended to normalize the photos geometrically so that fiducial marks have the same pixel coordinates on all the photos. Unfortunately, PhotoScan currently doesn't support automatic fiducial marks detection, so this normalization should be performed in the external software.

With best regards,
Dmitry Semyonov
AgiSoft LLC