November 2008 •
Lighting&Sound
America
TECHNICAL FOCUS: PRODUCT IN DEPTH
decision to me, but I guess the Martin
marketing moguls decided that it wasn’t
necessary for the target market. As a
strobing shutter it works fine, and
provides a measured strobe range of
1.2Hz to 8Hz.
(Note: I asked Martin to comment on
the lack of a dimmer. The official position
on this is that the main design criteria for
the smartMAC were high output and
wide beam angle, and the optical design
to achieve that in the small package
precluded a dimmer. Martin determined
that a dimmer provided less value for the
smartMAC´s core applications and would
not generate sufficient benefits to justify
the additional price to the customer.)
Gobos
Next in line is the rotating gobo wheel.
The smartMAC wheel has six replaceable
rotating gobos plus the open aperture.
Every gobo assembly slides out easily for
replacement (Fig. 7), and each of the
gobos has its own sensor magnet so
that it can be aligned for indexing—you
can see the magnet as the small square
at the bottom of Figure 7. The unit
comes as standard with a mix of metal
and glass gobos, so is clearly capable of
taking custom designs in either material
(Fig. 8). Again, with one of the uses being
retail display, this is a key point. I’m sure
Martin made the gobo change so easy to
address this market’s needs.
Positioning and indexing accuracy on
the rotating gobos was good, with a
measured hysteresis error of around
0.26°, which is 1.1" at a 20' throw.
Rotation and indexing of gobos was also
smooth and clean at all speeds, with no
evidence of jerkiness or hesitation. The
slow-speed gobo rotation was
particularly impressive. The wheel spin
was a little jerkier, but it didn’t worry me
too much.
One attribute that I found slightly
different from other moving lights was
the very large gap between gobos that
was noticeable when rotating the wheel
slowly. One gobo almost completely
disappears, leaving a black screen
before the next rises into view. You can
see when doing this that the actual
projected beam width is about twice that
of the open aperture, so there’s quite a
lot of vignetting going on. I’m not sure if
this is deliberate on Martin’s part—so
that it behaves a little like a slide
projector—or whether it’s just a function
of the engineering decisions on wheel
sizes. The novel access to the gobo and
color-change system pretty much
requires that the two wheels are of equal
size, so that constraint may have driven
this design. I also noticed some focus
difference between gobos—this is
undoubtedly driven by the mix of
materials, with metal gobos focusing
differently from glass ones. It’s not a big
deal, as the smartMAC has remote focus
capability, but one should take care
when programming.
Now is perhaps a good time to talk
Fig.8: Sample gobos.
Fig.9: Effects access.
Fig.10: Small fingers required
Fig.11: Changing gobo.
Rotating Gobo
Gobo change time,
adjacent apertures 0.3 sec
Gobo change time,
max (Gobo 1 to 4) 0.72 sec
Max gobo rotate speed 0.5 sec/rev = 120 rpm
Min gobo rotate speed 508 sec/rev = 0.12 rpm = 7 rph
Max wheel spin speed 0.8 sec/rev = 75 rpm
Min wheel spin speed 840 sec/rev = 0.07 rpm = 4.3 rph
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