116 vs. 716 (part II)

[P3D Dr. George A. Themelis <fj834@xxxxxxxxxxxxxxxxxxxxx>]

Regarding lenses, image size and brightness:

Each projector can be used with either 5" or 4" lenses.  I do not think
that the 716 came with 4" as a default.  I have seen plenty of 116s with 4"
and 716 w/5" lenses.  

What is the difference between the two?  Only one thing: Image size.  The
shorter lenses will project a larger image from the same distance from the
screen or can be placed closer to the screen to fill it with the image.

How about brightness?  Well, image brightness is inversely proportional to
image size.  FL of lenses has nothing to do with brightness.  What Ken did,
i.e., comparing the brightness of the two projectors from the same distance
from the screen, in my mind is invalid.  To compare the brightness of the
two images you must project them to the same size.  Once projected to the
same size, I am sure the 750W bulbs project a brighter image.

Which FL should you choose? 

If space is not a problem, the projector can be placed anywhere so that the
image fills the screen.  The audience can sit anywhere too.  So the only
difference is that the projectionist will be seeing a smaller image with
the longer lenses.  In practice, many houses do not have enough room, so,
in order to fill the screen in a small house/room you need the shorter
lenses.  In a club, space is usually not a problem and longer lenses are
preferred so that the projector is in the back and the audience in front of
it.

At home I have been using the 116 and 50" screen.  Recently I bought a 70"
screen.  I manage to fill it nicely by putting the screen in one wall and
the projector at the very end of the room.  Later, I tried the 4" lenses
and was able to put the projector closer to the screen.  I liked being able
(as a projectionist) to see a larger image.  However, I think I will stick
with the 5" lenses which are more flexible for home and club/big projection
use.

In any case and with any projector, I recommend the 750W bulbs for 50x50
or, especially, larger screens.  With the 70x70 the image is very dim if
500W bulbs are used.

To be continued...


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