This page contains details about how to adjust my panorama hardware to position the entrance
pupil of the lens in a position where it can be rotated around two axes without moving from
its position (the “no-parallax point”). The values are specific to my hardware, but the
principles aren't.
First I need to mount the camera, an Olympus E-30, on my hardware,
consisting of a cheap, badly designed panorama bracket and a couple of focusing rails to
compensate for the design errors of the bracket. The camera is mounted on one of two
different “Fotomate” rails (more of that below) which in vertical orientation fits into the
mount of the upper rotator of the panorama head (the L-shaped frame on the left):
The panorama bracket comes with a useless rotator which is not adjustable in position along
the rail to which is mounted. It is wrong for anything I want to do. I haven't been able
to remove it, so I have just locked it in position so that it doesn't rotate and mounted it
on a 16 cm Fotomate rail, which in turn is screwed to a Sunwayfoto DDP-64M rotator below (not visible here, but directly below the plate with “FOTOMATE” written on
it), which does work well. The toy rotator is the cylinder round offset 8 mm on the rail.
Horizontal centring
For this particular hardware and (vertical) orientation, the camera is centred above the
rotator when the scale is set to 4.4 cm. In horizontal orientation it needs to be
readjusted to 5.8 cm:
In horizontal orientation, it's also important to ensure that the axis of the lens is at the
height of the upper rotator (or the toy vertically mounted compass attached to the clamp).
In vertical orientation this happens automatically.
The position of the camera along the upper rail depends both on the lens and on the rail I
choose. The following is an adaptation of the information at http://olypedia.de/Nodalpunkte_E_System. It reduces to readings on the scale of
the 16 cm Fotomate rail:
This rail has a distance of 108 mm from the tripod mounting hole when the scale is set on 0
and the camera is mounted at the far end of the adjustable slot. The scale is the wrong way
round, so the distance reduces as the scale indication increases. In addition, the tripod
mounting hole of the E-30 is 4 mm behind the sensor plane, so this value needs to be added.
The real value is thus offset = 108 + 4 - scale, or scale = 108 - offset -
4.
The magic here is a little function that converts the individual values in the table, so
that I don't have to do it manually:
Focal length
7-14
8mm
9-18
11-22
12-60
14-35
14-42
14-45
14-54
25mm
35mm
50mm
7 mm
-24
8 mm
-21
12
9 mm
-19
7
10 mm
-18
11 mm
9
-9
12 mm
-19
-8
14 mm
-19
10
-4
28
6
6
16 mm
7
18 mm
5
1
1
30
6
13
22 mm
6
25 mm
8
30
6
24
52.8
35 mm
18
34
-1
35
55
42 mm
48
45 mm
-6
50 mm
36
43
54 mm
50
60 mm
44
I can't set negative values (the ones marked in red), so for those values I need to use a
longer rail (26 cm), again from Fotomate:
This one is presumably meant for mounting flash units. As shown, it is set with the
mounting hole directly below the inside end of one of the slots. The scale shows 9 mm left
of the 0 point on the scale. If I mount the camera in this position, at the right end of
the left slot, and point it to the right, I can move the base of the rail as far as 121 mm
in that direction (not quite to the end of the scale), giving me a total range of 130 mm.
In this case the calculation is more straightforward: offset = 108 + 4 - scale,
or scale = offset + 4 - 9.
Focal length
7-14
8mm
9-18
11-22
12-60
14-35
14-42
14-45
14-54
25mm
35mm
50mm
7 mm
123
8 mm
120
87
9 mm
118
92
10 mm
117
11 mm
90
108
12 mm
118
107
14 mm
118
89
103
71
93
93
16 mm
92
18 mm
94
98
98
69
93
86
22 mm
93
25 mm
91
69
93
75
46.2
35 mm
81
65
100
64
44
42 mm
51
45 mm
105
50 mm
63
56
54 mm
49
60 mm
55
This rail can be set for all the values in the table above, with the exception of the 7-14
mm lens set at 7 mm. I could fix that easily by repositioning the camera, if I had
that lens. But I still can't use it all the time: it's too long for vertical shots, and I'm
not sure that I wouldn't get it in the field of view of my 9 mm lens.
