Second, the wider the blend line, the easier it is to
maintain its quality and the less visually apparent small deviations from
perfection become. The present blend line is extremely difficult to control and
should be increased by at least 50%.
Third, everyone should be convinced by this time that
neither the camera nor the projector should have any aperture or vignetting
encroaching on the space allotted for the printer blend line. The effect are
additive, and in the presence of an otherwise perfect blend, the spurious
vignetting effects are plainly visible. There are numerous examples in the
picture. In this case, the projector can be corrected readily and permanently.
However, such effects in the camera are permanently recorded on the negative,
and can rarely be corrected in the printer which must never be considered a
corrective device. An obvious
corollary is that the camera overlap at its narrowest must be wider than the
printer vignette for all focus and aperture settings.Fig. 7. This is of particular importance at the
closest focus distance where the camera overlap is the least, and at the widest
lens aperture where camera vignetting extends into the overlap area and
is further aggravated by distortion. These effects are shown in Fig. 8.
Since the printer vignette width is already somewhat too
narrow for good control, it is necessary for the cameras to be readjusted to
provide a greater overlap free of camera vignetting if improvement is to be
made in matchlines. There is no alternative. The requirement is fundamental.
True, an increase in overlap simultaneously increases
parallax. However, this picture demonstrates that the presence of a perfect
blend line, mismatching due to parallax is difficult to find particularly with
skillful camerawork. In fact, many of the most obvious mismatch errors have not
been due to parallax but to gross camera positioning errors.