P3D Re: white LEDs

[Greg Erker <erker@xxxxxxxxxxxxxx>]

>>There are other factors to consider.  Price doesn't seem to be one.
>
>This sounds like conjecture.  My comments are based on experience.
>
>You are going to need a bank of white LEDs, not just one. Depending
>on how bright you want your image, you'll need a handful.  This adds
>up to real money fast.

  Tom H. is talking about using a single LED
per side and condensor optics to project all
of the emitted light through the film chip.
This is much more efficient than bouncing the
light off a white reflector or diffusing it
with white or frosted plastic or glass.

  So without doing any calculations it seems
that it may well be feasible to get decent
brightness with a single LED lighting a 5perf
Realist image. I have my doubts about 7 or 8
perf or 50x50mm medium format.

  Which format (or all) are you saying need
a bank of white LEDs?

>The cost of the array of white LEDs, the color balancing LEDs, and
>the rest of the regulating circuitry needed to run them is *many*
>MANY times more complex and expensive than the simple bulb in a
>regular viewer.

  The HP LEDs claim a CRI of 75 and the Nichia
ones claim 85. A halogen bulb with a blue correction
filter could do better but a fluorescent tube
not made for a light box (eg. camping lantern)
is likely to be worse.

  So, without ever having seen a white LED, it
seems to me that it may be possible to use them for
viewer lighting without colour balancing LEDs.

  Do you know the CRI of the LEDs you used?

>This isn't theory.  I have easily spent 100 hours on this, and as
>many dollars. There is much more to it than meets the eye, NPI.

  Wasn't this for a medium format viewer or
do I miss-remember?



>Ignore the hype.  Don't hoard food, leave your money in the bank, and
>put the gun back in the attic. The big story on January 1 will be
>that nothing happened.

  That may well be true in North America
but I suspect more than nothing will happen
in parts of Africa, Asia and eastern Europe.

Greg E (just my opinions)