P3D Re: Comparing projectors/screens

["Dr. George A. Themelis" <DrT-3d@xxxxxxxxxxxxxxxxxxxxxxxxxxx>]

Thanks Les Gehman for the interesting reporting on your testing of 
screens/projectors.

>This makes me think that once the image quality is "good enough",
>whatever that means, brightness is next thing to work on.  

I agree. I am happy with the sharpness of my 5" TDC and I would 
like to increase the brightness.

A few months ago I posted a number of observations/mesurements
from my experiments with my TDC.  One surprising result was that
the image brightness using 500W bulbs was almost identical to the
one using 750W bulbs in the same projector.  I did the measurements
using my 116 but since then I have repeated those measurements using
a 716 and got the same results.  You might see a difference of .1 to
.2 EV maximum.  This puts under question the use of 750W bulbs, 
considering the damage in the slides, projector and electric bill.

Here is an idea:

Since many of us use these fancy digital light meters perhaps we can
establish a common method to measure intensity of light from the
projector.  All we need to know is the intensity for a given *image
size*.  Put our meters in EV mode for say ISO 100 seeting and record
the reading.  How does that sound?

There are a few things you can do to improve the projector. Make sure
that you clean all the lenses/filters and also the reflective mirror 
behind the lamps (you might need to align it too).

Drastic changes are described in Steve Spicer's excellent web page.
Steve claims that you can use low voltage 150W bulbs with smaller 
filaments and get brighter and sharper images!  Check:

http://www.werple.net.au/~kiewavly/TDC1.html
 
Regarding screens, I played with the few that I had around the house.
Some older ones were brighter at the dead center but dimmer off center.
That's not good IMO.  New screens sold by Da-Lite are very good IMO.
I have the 70" Picture King and I am very happy with it.  As a backup
I am keeping a 50" Da-Lite but always use my 70".  For $170 you are
getting an excellent screen for a good price.
   
George Themelis


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