Forum

Poll

The Agiosft Tutorial recommends to set focal length of a used zoom lens either to maximum or minimum value

General
0 (0%)
focal length
1 (100%)

Total Members Voted: 1

Author Topic: Capturing Photos with zoom lenses  (Read 1966 times)

Bibi

  • Newbie
  • *
  • Posts: 2
    • View Profile
Capturing Photos with zoom lenses
« on: November 01, 2017, 03:05:44 PM »
The Agiosft Tutorial recommends to set focal length of a used zoom lens either to maximum or minimum value -what is the reason behind this recommandation?
« Last Edit: November 01, 2017, 03:45:25 PM by Bibi »

Alexey Pasumansky

  • Agisoft Technical Support
  • Hero Member
  • *****
  • Posts: 13190
    • View Profile
Re: Capturing Photos with zoom lenses
« Reply #1 on: November 01, 2017, 05:08:22 PM »
Hello Bibi,

When zoom-lens is set to the intermediate focal length position, it may change slightly due to the camera shake, but the EXIF metadata will contain the same values due to the rounding to 0.1 mm or even to 1 mm. It means that practically two images are captured with the different focal length, but would be put to the same calibration group according to the EXIF information.

In case zoom-lens is used it may be reasonable to split the camera calibration group, if the alignment result is inaccurate.
Best regards,
Alexey Pasumansky,
Agisoft LLC

Smallpoly

  • Newbie
  • *
  • Posts: 32
    • View Profile
Re: Capturing Photos with zoom lenses
« Reply #2 on: November 01, 2017, 09:34:26 PM »
Adding onto that, you can also help prevent the focal length from changing by securing it with some painter's tape.