Instructions to Define the Nodal Point
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Instructions to Define the Nodal Point Roundshot Super 220 VR Software Release 4.0 and higher © by Seitz Phototechnik AG, Hauptstr. 14, 8512 Lustdorf, Switzerland, Phone: +41 52 376 3353, Fax: +41 52 376 3305, [email protected], www.roundshot.ch Technical changes reserved, Released: 1.2005 Page 0 1. Introduction 1.1 What is a nodal point? The term „nodal point“ defines the optical centres of a lens where the incoming light is bundled in the optical axis. First nodal point (H’) Second nodal point (H) The first (front) nodal point is the The second (rear) nodal point is the position on the optical axis of a position on the optical axis of a lens lens where the entering ray where the departing ray crosses the crosses the optical axis. optical axis. Film plane Focal length Thedistance fromthesecond (in mm) nodal point to the focal point (film plane) is the focal length. 1.2 What is the significance of the nodal point for panoramic photography? For rotational panoramic photography of up to 360° the camera head with the lens rotates around a vertical axis. For optimum sharpness the nodal point needs to be exactly at the centre of this axis. If the nodal point is not situated exactly at the centre of the rotation axis, a so-called parallax effect occurs. When rotating the camera the distances between vertical lines change and sharpness as well as depth of field decreases. Good nodal point: Bad nodal point (parallax effect): © by Seitz Phototechnik AG, Hauptstr. 14, 8512 Lustdorf, Switzerland, Phone: +41 52 376 3353, Fax: +41 52 376 3305, [email protected], www.roundshot.ch Technical changes reserved, Released: 1.2005 Page 1 2. Procedure to define the nodal point for the Roundshot Super 220 VR with Software Release 4.0 and higher The Roundshot Super 220 VR camera makes it possible to fit lenses of 13mm up to 1,000 focal length of a variety of manufacturers. The nodal point of these lenses is always different. For optimum depth of field the camera head is moved forward and backward on the optical bench to centre the nodal point of the lens in the rotation axis. Movement of camera head Optical bench (with scale for b-values) Up to Software Release 3.97 the second nodal point was the reference and the b-value was calculated using a mathematical formula. Camera tests have revealed that rotating in the first nodal point allows an even better sharpness and depth of field. That is why – with Software Release 4.0 and higher – the first nodal point is taken as a reference. This nodal point is defined empirically / optically. © by Seitz Phototechnik AG, Hauptstr. 14, 8512 Lustdorf, Switzerland, Phone: +41 52 376 3353, Fax: +41 52 376 3305, [email protected], www.roundshot.ch Technical changes reserved, Released: 1.2005 Page 2 2.1 Defining the nodal point for the Roundshot Super 220 VR with Software Release 4.0 and higher Define two points in space that lie behind each other. Ideally take vertical lines (such as houses, poles, pillars etc.) at a distance of about 2m and 6m. Focus at 4m. Position the Super camera in such a way that the two lines are exactly behind each other. The line should be either on the very left or on the very right of the viewfinder. Rotate the camera head and observe in the viewfinder (ideally with magnifying glass) how the two lines behave. If the two lines are still exactly behind each other, then the nodal point is found. If not, change the position of the camera on the optical bench (forward or backward) and repeat the procedure until the lines are exactly aligned. Good nodal point: Bad nodal point: Distance unchanged after rotation Distance changed after rotation © by Seitz Phototechnik AG, Hauptstr. 14, 8512 Lustdorf, Switzerland, Phone: +41 52 376 3353, Fax: +41 52 376 3305, [email protected], www.roundshot.ch Technical changes reserved, Released: 1.2005 Page 3 2.2 Read the b-value and enter it in the Super Software Example: Nikkor 28mm PC Shift f/3,5 Read the b-value on the scale of the optical bench. B = 72 Open the lens list of the Roundshot Super Software. Enter the effective focal length* of your lens in the list (for example 28.6mm) and press button „D“ to save. * A list of effective focal lengths and a simple empirical approach to determine effective focal length is given in the Appendix; this data has been collected from manufacturers data sheets (where available) and from Seitz research; due to the wide variety of available lenses and the sometimes difficult access to lens data no warranty can be given as to the completeness and exhaustiveness of data © by Seitz Phototechnik AG, Hauptstr. 14, 8512 Lustdorf, Switzerland, Phone: +41 52 376 3353, Fax: +41 52 376 3305, [email protected], www.roundshot.ch Technical changes reserved, Released: 1.2005 Page 4 Enter now the h-value. This value is calculated as follows: h-value = b-value Effective focal length (mm) (mm) (mm) 43.4 72.0 28.6 The h-value is a correction value to bring the nodal point exactly into the rotation axis. Press button „D“ to save. © by Seitz Phototechnik AG, Hauptstr. 14, 8512 Lustdorf, Switzerland, Phone: +41 52 376 3353, Fax: +41 52 376 3305, [email protected], www.roundshot.ch Technical changes reserved, Released: 1.2005 Page 5 Open the list of distance values, enter the focusing distance and press button „D“ to save. As a result the optimum b-value is displayed again. The optimum nodal point for your lens is now saved in the software and can be accessed any time again. © by Seitz Phototechnik AG, Hauptstr. 14, 8512 Lustdorf, Switzerland, Phone: +41 52 376 3353, Fax: +41 52 376 3305, [email protected], www.roundshot.ch Technical changes reserved, Released: 1.2005 Page 6 Repeat this procedure for all of your lenses and check the sharpness using test film. At closer distances (for example 1m instead of infinite) the lens has a longer effective focal distance. This means that the b-value is increased by this difference (for example 29.4mm when focusing at 1m instead of 28.6mm at infinite distance for Nikkor 28mm PC Shift f/3,5). Hence slightly different b-values are obtained for different distances. However, in reality these differences are not significant and can be ignored. A tolerance of +/- 1mm on the optical bench cannot be detected by the human eye when defining the nodal point optically and leads to identical depth of field. When using very wide angle lenses it is possible that the camera head moves back to the very end of the optical bench and that the control unit and the battery appear in the image. This can be solved by detaching control unit and battery with an external cable (article number 3084 and 3085) from the camera engine. The b-values for the saved lenses with their respective distance settings can be accessed in the Software at all times. The Super Software can accomodate up to 20 lenses. When changing lenses these values can be retrieved and the optimum nodal point can be set on the optical bench. We are convinced that this new procedure to define the nodal point will produce very good results and wish you continued success and fun with your Roundshot Super 220 VR. © by Seitz Phototechnik AG, Hauptstr. 14, 8512 Lustdorf, Switzerland, Phone: +41 52 376 3353, Fax: +41 52 376 3305, [email protected], www.roundshot.ch Technical changes reserved, Released: 1.2005 Page 7 Appendix A: Lens Lists The following tables are worksheets for your own selection of lenses. Wherever available we have listed the effective focal length. This data has been collected from manufacturers data sheets (where available) and from Seitz research; due to the wide variety of available lenses and the sometimes difficult access to lens data no warranty can be given as to the completeness and exhaustiveness of data. You can fill in your own values in the colums „B-Value“ and „H-Value“ for future reference. © by Seitz Phototechnik AG, Hauptstr. 14, 8512 Lustdorf, Switzerland, Phone: +41 52 376 3353, Fax: +41 52 376 3305, [email protected], www.roundshot.ch Technical changes reserved, Released: 1.2005 Page 8 Nikon Nikkor Lens Focal length Minimum Effective focal length B value H value aperture "f" determined optically H = B - f mm f mm mm mm Nikkor 13 5,6 13.3 Nikkor 15 3,5 15.4 Nikkor 18 3,5 18.1 Nikkor 20 2,8 20.3 Nikkor 24 2,0 24.5 Nikkor 24 2,8 24.6 Nikkor 28 2,0 28.4 Nikkor 28 2,8 28.7 PC Nikkor 28 3,5 28.6 Nikkor 35 1,4 35.8 Nikkor 35 2,0 35.7 Nikkor 35 2,8 35.4 PC Nikkor 35 2,8 36.4 Nikkor 50 1,2 51.6 Nikkor 50 1,4 51.6 Nikkor 50 1,8 51.5 Micro Nikkor 55 2,8 55.0 Noct Nikkor 58 1,2 57.9 Nikkor 85 1,4 84.9 Nikkor 85 2,0 85.0 Nikkor 105 1,8 104.9 Nikkor 105 2,5 105.0 Micro Nikkor 105 2,8 105.4 Micro Nikkor UV 105 2,8 105.1 Nikkor 135 2,0 135.1 Nikkor 135 2,8 135.1 Nikkor 135 3,5 135.1 Nikkor 180 2,8 180.2 Nikkor IF-ED 200 2,0 199.4 Nikkor 200 4,0 199.5 Micro Nikkor 200 4,0 201.5 Nikkor IF 300 4,5 299.9 Nikkor IF 400 2,8 400.2 Nikkor IF 400 3,5 400.1 Nikkor IF 400 5,6 400.1 Nikkor IF 500 4,0 495.5 Reflex Nikkor 500 8,0 520.0 Nikkor IF 600 4,0 602.0 Nikkor IF 600 5,6 601.0 Nikkor IF 800 5,6 801.5 Reflex Nikkor 1000 11,0 999.7 © by Seitz Phototechnik AG, Hauptstr.