Re: 116 vs 716

[P3D KENNETH LUKER <KLUKER@xxxxxxxxxxxxxxxxxxxxxxx>]

> >My conclusion:  The larger but dimmer image of the 716 is not 
> >sufficiently better than the slightly brighter, smaller image of my 
> >16 to motivate me to change projectors.
> 
> are based not on projector characteristics but on projector "accessories"
> (light bulbs and lenses) which are interchangeable.
replied George.

I agree.  My conclusion was that for me, who have already moved the 
projector as far from the screen as my home allows, I prefer the 
slightly brighter picture to the considerably larger but somewhat 
dimmer image.  Others may have more space, or may prefer size over 
brightness.  The longer lenses give me an image that is large enough 
to suit me (50 x 50), although I would OF COURSE prefer a larger 
image if it did not have to be at the expense of brightness.

> I believe that the two projectors have identical electrical, mechanical and
> optical components except for two things:  The 716 has ceramic lamp holders
> vs. plastic (bakelite) for the 116. 

In fact, this isn't exactly true.  The 116 has a circular metal tube 
around each lamp that gives a rather close fit to 750W lamps, but has 
plenty of room around the 500W lamps.  In the 716, the corresponding  
shroud is a square metal tower with the front side removed, and is 
considerably farther away from the center of the socket.  I don't 
recall the exact size, but the square shroud seemed to have about the 
same clearance for the 750W lamps as the circular shroud had for the 
500W lamps.

> Some people have reported cracking of
Date: Thu, 19 Dec 1996 16:29:53 -0600
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> the holders in the 116.  I have not experienced any such thing in the
> 116+750 W bulbs that I have used.  The 716 has a 3-way switch that allows
> you to run the fan with the bulbs off.  I have modified my 116 for a 3-ways
> switch and I ran the fan w/out the bulbs to cool the projector but don't
> know if this has any effect on anything.  

I've modified my 116 similarly, except that I just bypassed the lamp 
switch so that the fan is on whenever the projector is plugged in.

> The main heat-related components of the two viewers (fan, heat absorbing
> filters) are identical or equivalent.  I can see the difference and I
> prefer the 750W bulbs, especially with my new 70" screen!!!
> 
I have a very large screen too, but I can't fill it with the 5 inch 
lenses in my house.  If I could switch lenses, I would (maybe I can 
negotiate a swap with my neighbor!).  But I don't feel willing to 
sacrifice the brightness for the size, given a fixed distance from 
projector to screen.  I especially would not want to get the shorter 
lenses if it were not possible to simultaneously get the brighter 
lamps.  But that IS possible, I agree.  'Twould  be nice if getting 
brighter lamps and shorter lenses would give both a bigger picture 
and a brighter picture.  My side-by-side trial dashed that hope.

>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. 

I believe that what I did was not only valid, but was exactly what I 
had to do to find which was brightest when the projectors were the 
same distance from the screen, namely, at the back wall of the living 
room.  I could have calculated the result by figuring something like 
watts per square inch of screen, but I wanted to SEE it, and besides, 
it was easier. :)

> 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.

Ah, NOW you get it!  :)  :)
To generalize, use bright lamps or move close to get a bright image, 
and use short lenses or move farther away to get a big picture.  When 
you must compromise, you must compromise.  I suppose what I COULD do 
is to buy the brighter lamps and shorter lenses, then move the 
projector closer to the screen until the image is as bright as I like 
it.  But that would cost me bucks, and I can choose whether the 
improvement in satisfaction is equivalent to the bucks it would cost. 
I merely expressed my preference.  (It may change.)

Ken Luker _______________________________________________________________

Kenneth Luker, Assistant Director
Systems and Technical Services
Marriott Library
University of Utah
Salt Lake City, Utah
KLUKER@xxxxxxxxxxxxxxxxxxxxxxx


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