Instruction manual

Instruction Manual Roundshot D3 - version 4.05 – May 2013 - © by Seitz Phototechnik AG / Switzerland www.roundshot.ch page 54
How to determine the effective focal length and rotation point empirically
Many medium format lenses are calibrated at the factory and their effective focal length
and rotation points are programmed in the Seitz Roundshot D3 software.
For lenses that are not in the software or in the lens lists it is also possible to determine
the effective focal length empirically. This can be done in the following way:
Step 1: Set up a square table at a distance of a few metres on a wall (exactly 90°
angle to camera). On the table draw a cross (for example, exactly 1m vertical, 1m
horizontal):
1m
1m
Step 2: Centre the optical axis of the Roundshot D3 camera exactly at the centre of
the cross. Focus on the cross and change the distance in the software. Use TDI Stages
1x as this minimises the potential error of a wrong rotation point). Enter the effective
focal length in the Seitz Roundshot D3 software, starting for example with f=28.0
4.2 … obtain the best sharpness (continued)