Slide projectors
How to choose a slide projector
Comparing
slide projectors from spec sheets is a little more difficult than
you might expect, because the items you most want to compare–image
quality, brightness, and reliability–aren’t given in the specs.
On the other
hand, the technology has come far enough that these three items
really aren’t a big issue. If you stick with a projector built
for professional use, the main question becomes one of the features
you need versus the budget you have available.
The most
important specifications
- The focal
length of the lens you choose for your new projector determines
the screen size you can fill at a given distance. The following
table shows the approximate throw distance needed (from film
plane to screen) for various screens and focal lengths.
| Screen
width |
| Lens |
60" |
70" |
84" |
96" |
| 35 mm. |
5.2 |
6.0 |
7.3 |
8.3 |
| 50 mm. |
7.4 |
8.6 |
10.4 |
11.9 |
| 90 mm. |
13.3 |
15.6 |
18.7 |
21.3 |
| 100 mm. |
14.8 |
17.3 |
20.7 |
23.7 |
| 150 mm. |
22.2 |
25.9 |
31.1 |
35.6 |
| 200 mm. |
29.6 |
34.6 |
41.5 |
47.4 |
| 250 mm. |
37.0 |
43.2 |
51.9 |
59.3 |
Because most
people use their projectors in different rooms at different times,
zoom lenses are the most popular United sells.
-
Compatibility
can be an issue if you plan to use your projector with a dissolve
unit or multi-image programmer, particularly if you’re considering
a projector mainly intended for home use. By and large, the
projectors in this catalog will work with the majority of
programmers available, but it makes sense to check before
you buy.
-
Slide
changing time refers to the minimum time it takes to cycle
each slide in and out of the projection gate. This, again,
is a consideration if you’re planning to use your projector
with a multi-image program.
Useful
features
-
Remote
focus can be extremely useful, as most people find it easier
to focus their projector accurately while standing close to
the screen than from the back of the presentation room.
-
Auto
focus can also simplify the setup process, but is most useful
as a means to ensure that each slide in a given tray stays
in as sharp a focus as the first.
-
An extra
lamp module will allow you to get up and running quickly should
a projection lamp fail during a presentation. (Simply pull
out the whole module and slide in the new.) The newer Ektapro
projectors can include a dual-lamp module, which automatically
switches to a new lamp when the old one fails.
-
A preview
screen allows you to look at a tray of slides in your presentation
room without having to show them to your audience.
-
A reading
light is not actually for reading, but is included to allow
you to identify a tray or look at an individual slide in a
darkened room.
-
Random
access allows you to project any slide in your tray at any
time.
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