Surprise! (TDC image brightness)

[P3D Dr. George A. Themelis <DrT-3d@xxxxxxxxxxxxxxxxxxxxxxxxxxx>]

Well, I did my measurements and concluded that the 750W bulbs
are *not* brighter than the 500W bulbs in my TDC 116 projector....

At first I used a new uncleaned projector which I just got
with 500W bulbs.  I could tell that this was dimmer than my
750W equiped projector and measurements confirmed that.  However,
when I opened it to remove the bulbs I noticed that one lens
was off track.  This side was giving lower light output than
the other.  After I put the lens back in track, the light output
increased but still did not match my 116 w/750W bulbs.  However,
when I replaced the 750W bulbs in my projector with the 500W bulbs
I measured the same light output, 6.2EV w/ASA 100.

There are several lessons here:  Lens alignment is important,
clean lenses and mirrors are important. Also, the age of the
bulbs is important too.  One thing I noticed is that if I cover
one lens, the light output is lower compared to the output if
I turn this lens off.  That shows that there is a voltage drop
at high current coming from either the projector or the line.

At the end I do not know why the two sets of bulbs are giving
the same light output even though one is rated higher than the
other...  This being the case, it is better to use the lower
wattage bulbs which are less demanding on the projector, slide
and electric bill!

More experiments are in order... I would like to see if the
TDC 716 gives out more light compared to the 116 using the
750W bulbs...  Also, I would like to explore other bulb
options per Steve's posting.

George


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