Brightness of viewers

[P3D <PTWW@xxxxxxx>]

I have compiled the following (pseudo)-scientific data regarding relative
brightness of some stereo slide viewers.

 EV value (at ISO 100) of various stereo viewer/light source combinations:
 ------------------------------------------------------------------------

Viewer  light source      conditions                          peak reading
------  ------------      ----------                          ------------

T'dRB   frosted halogen    batteries @ 1.58 volts                 12.6
T'dRB   frosted halogen    batteries @ 1.49 volts                 12.2
T'dRB   frosted halogen    batteries @ 1.33 volts                 11.0
T'dRB   GE14 round bulb    batteries @ 1.33 volts                 10.0

RB      GE14 round bulb    batteries @ 1.58 volts                 10.0
RB      GE14 round bulb    batteries @ 1.58 volts; T'd top piece  10.3
RB      frosted halogen    batteries @ 1.58 volts                 11.0
RB      frosted halogen    batteries @ 1.58 volts; T'd top piece  11.9

$3      60W incandescent   0 inches, bulb directly behind 1 lens  16.1
$3      60W incandescent   0 inches, bulb centered behind lenses  14.8
$3      60W incandescent   6 inches, bulb centered behind lenses  11.5
$3      60W incandescent  12 inches, bulb centered behind lenses   9.5
$3      60W incandescent   6 feet, white lamp shade in place       5.6

$3      30W flourescent    0 inches from circular tube            14.7
$3      22W flourescent    0 inches from circular tube            14.0

$3      4x??W flourescent pointed at office lights from chair      8.6

$3      bright sun         directly into                           16.2
$3      blue sky          180 degrees from sun                     15.0
$3      blue sky           90 degrees from sun                     15.5


Notes:
-----
All measurements taken near the center of the left lens of an empty
viewer.

Peak value, rather than an average of many readings, was used for
simplicity.  The peak value was generally hit only once, but normally
exceeded the next highest reading for the same viewer/light source
combination by only .1 EV.  A cluster of readings about .3 to .5 EV
below the peak reading was typical.

Light values fall off as readings are taken away from the center of the
lens, usually by about 1.0 EV.

RB used for these measurements had fogged lenses, which may partially
explain the variation between the 11.9 maximum reading for the RB with
halogen lamp and T'd top piece, vs, the 12.6 T'dRB maximum.  Other DrT
modifications, such as the white painted inside bottom of the reflector
compartment area, may account for the rest of the difference.

Note that the halogen lamp and the T'd top piece have a synergistic
effect.  The T'd top piece had little impact when used with the GE14 bulb.

I do not know the age of the GE14 bulb.  DrT can probably supply the age
and rating of the frosted halogen bulb.  It is probably very new and the
brighter of the bulbs he offers.

I did not attempt to determine the maximum viewing time or wattage values
the $3 viewer can tolerate before melting.  Exercise due care to avoid
damage to the viewer or yourself when replicating these tests.

1.0 EV difference in brightness as not as significant viewing a slide as
it does in exposing slide film.  Based on personal experience, however,
a slide that appears acceptably exposed at 11.0 can seem quite noticeably
overexposed at 12.6.

Paul Talbot, not a scientist, never even played one on TV

P.S.  Sorry, I do not at this time have any tips for making your T'dRB
as bright as a $3 viewer with a close or bright light source.  ;)


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