Characteristics of Incandescent Lamps
as a Function of Various Voltages

Table of Contents

Amps, lumens and color temp. of 120V 100 watt 750 hour A19 lamp
Amps at various voltages of 120V 25 watt 2500 hour A19 lamp (gas filled)
Amps at various voltages of 120V 25 watt 750 hour T10 lamp (vacuum)
Explanation of how data was obtained

Lamp:  100 watt A19, 120V, clear, Sylvania, filament CC-8, lamp vertical
Updated 4/27/2020.
------------------------------------------------------------------------
Volts      .5    1    1.5   2    3   4.5   6    9   12   15   18   24   30   36   42   48   60   72   84   96   108  120  132   144   160

Amps      .047 .083  .108 .126 .152 .177 .196 .227 .254 .280 .304 .350 .394 .433 .470 .505 .571 .631 .688 .740 .788 .834 .878  .921  .976

% Volts  .4167 .8333 1.25 1.667 2.5  3.75  5   7.5  10  12.5  15   20   25   30   35   40   50   60   70   80    90  100  110   120  133.3

% Amps   5.63  9.95 12.95 15.1 18.2 21.2 23.5 27.2 30.5 33.6 36.5 42.0 47.2 51.9 56.4 60.6 68.5 75.7 82.5 88.7 94.5  100 105.3 110.4  117

log(i/I)/ .525 .482  .466 .461 .462 .472 .483 .502 .516 .525 .532 .539 .541 .544 .546 .547 .547 .546 .540 .536 .538  --- .539  .544   .547
log(v/120)

color temp. K (2011 determination)       ~800 ~977 1125 1245 1355 1528 1672 1800 1913 2015 2195 2360 2500 2635  2760 2875 2985  3085  3210

log(ct/CT)/   (2011 determination)       .43  .418 .408 .403 .397 .393 .391 .389 .388 .388 .388 .388 ~.39 ~.39  ~.39 ---- ~.39  .388  .383
log(v/120)

color temp. K (2020 determination)                                          1815 1935 2037 2215 2372 2515 2644  2763 2875 2980  3080

log(ct/CT)/   (2020 determination)                                          .382 .377 .376 .376 .376 .376 .376  .376 ---- .376  .376
log(v/120)

                                            ~1.25E-4
lumens (approximately, 2011)            ~8 E-7   ~.0033~.025 ~.12 ~.96 ~3.7 ~10.6  24   46  125  268  483  798  1218 1750 2405  3160  4310

log(lu/LU)/                              7.18 6.35 5.72  5.35 5.05 4.66 4.44 4.24 4.09 3.97 3.8 3.68  3.61 3.52 3.44 ---- 3.33  3.24  3.13
log(v/120) (approximately!)

lumens (approximately, 2020)                                                 11.5 26.5  51  133  281  507  820  1235 1750 2375  3115

log(lu/LU)/                                                                  4.17 3.97 3.86 3.71 3.58 3.47 3.39 3.31 ---- 3.20  3.16
log(v/120) (approximately!)

Lamp:  25 watt A19, 120V, clear, GE, filament CC-6, lamp vertical
------------------------------------------------------------------------
Volts      .5    1    1.5    2    3    4.5   6     9   12    15   18   24    30    36   42   48   60    72    84    96  108   120   132   144    160

Amps      .011 .0205 .0285 .035 .0455 .056 .0635 .073 .0795 .085 .090 .0995 .1075 .116 .124 .131 .146 .1595 .1725 .1845 .1955 .2065 .217 .2275   .240

% Volts  .4167 .8333 1.25  1.667 2.5  3.75   5    7.5  10   12.5  15   20    25    30   35   40   50    60    70    80   90   100   110   120    133.3

% Amps   5.33  9.93  13.8 16.95 22.0  27.1 30.75 35.35 38.5 41.1 43.6 48.2  52.1  56.2 60.0 63.4  70.7 77.2  83.5  89.3  94.7  100  105.1 110.2  116.2

log(i/I)/ .535 .482  .452 .434 .410  .398  .394  .401 .415 .428 .438  .453  .470  .479 .487 .497 .500  .507  .51  .51  .51-.52 ---  .52  .52-.53 .52-.53
log(v/120)

color temp. K                                                                                                                 2550

Lumens (approximately!)                                                                                                        210


Lamp:  25 watt T10, 120V, clear, GE, filament C-8, lamp vertical
------------------------------------------------------------------------
Volts      .5    1    1.5   2    3   4.5   6     9    12   15   18   24    30    36    42    48   60    72    84    96   108  120   132   144   160

Amps      .008 .012  .015 .018 .023 .029 .0345 .0445 .053 .061 .068 .0815 .0935 .1045 .1145 .124 .1425 .1585 .1735 .188 .201 .214  .226  .238  .252

% Volts  .4167 .8333 1.25 1.667 2.5  3.75  5    7.5   10  12.5  15   20    25    30    35    40   50    60    70    80    90  100   110   120  133.3

% Amps    3.74  5.61 7.00 8.41 10.75 13.6 16.1  20.8 24.8 28.5 31.8  38.1  43.7  48.8  53.5 57.9  66.6  74.1  81.1  87.9 93.9 100  105.6 111.2 117.8

log(i/I)/ .600 .602  .607 .605 .605 .608 .610  .606  .605 .604 .604 .600  .597  .596  .596  .596 .586  .587  .587 ~.58 .58-.59 --- ~.58   .58  .57
log(v/120)

color temp. K                                                                                                                 2550

Lumens (approximately!)                                                                                                        260

Explanations of How Color Temp. and Lumen Data Were Determined:

Color temperature in 2011:
This was done with the "Properties of Tungsten" table in the "Handbook of Chemistry and Physics", published by the Chemical Rubber Publishing Co.

In addition, plenty of interpolation was done.

Color temperature at full voltage for 100 watt 120V 750 hour A19 was assumed to be 2875 K because of mention of around 2875-2880 K in the IES Handbook. Kodak mentions 2865 K, but that dates back to when Standard Illuminant A was 2848 K, since redefined to 2854 K as a result of updating a constant in the blackbody formula.

Color temperature of coiled-coil filament in gas-filled bulb was assumed to be halfway between the actual temperature and the color temperature of a straight tungsten wire in vacuum at the same actual temperature according to the table.
Actual temperature at voltages other than full voltage were worked from filament resistance as a function of actual temperature according to the above "Properties of Tungsten" table.

Color temperature in 2020: updated 4/27/2020
Color temperature was determined at 120 volts and 60 volts with a spectrometer. As the voltage was changed from 120 to 60 volts, the color temperature was found to have changed proportionately with voltage to the .376 power. At voltages from 48 to 144 volts, color temperature was interpolated or extrapolated as being proportional to voltage to the .376 power.

Color temperature at 36 volts was measured with a spectrometer, at 42 volts was revised to an interpolation on 4/27/2020.

Color temperature of other lamps at full voltage largely come from color matching them to a 100 watt 120V A19 that is powered by an adjustable voltage power supply and use of my 2011 data for the above 100 watt lamp.

It is to be noted that the temperature is not completely uniform throughout the filament. It is also to be noted that the temperature profile of the filament varies with temperature since heat loss from radiation and conduction vary differently with temperature. As a result, color temperature and lumen figures are only roughly approximate, especially at more extreme voltages.

Lumens:

Color temperature was plugged into a homebrew BASIC program that has the blackbody function and the photopic function. "Color emissivity" (ratio of brightness of a given incandescent surface to a blackbody surface at the same color temperature) for a coiled-coil filament in a gas-filled bulb was assumed to be the square root of that shown in the "Properties of Tungsten" table for a straight wire in vacuum, for a given actual temperature. Color emissivity varies slightly inversely with temperature. This permits working of lumens at various filament temperature given color and assumed actual temperature and manufacturer's stated lumens at full voltage.
Brightness according to the brightness column in the "Properties of Tungsten" table varies even slightly more drastically with temperature than according to my homebrew BASIC program. UPDATE 4/26/2020: A light meter will soon be used to verify my determinations of how light output varies with voltage.

For Osram's version of the FEL lamp, updated 4/23/2020, more updating expected soon as of 4/26/2020.

Volts    Color temp K                     Lumens

  20      ~1615    (updated from ~1600)    ~14   (updated from ~11)
  24
  27      ~1820    (updated from ~1800)    ~76   (updated from ~63)
  28
  36      ~2025    (updated from ~2000)    ~300  (updated from ~248)
  48
  60      ~2490    (new line 4/23/2020)   ~2,990  (new line 4/23/2020)

 120      ~3200                           ~27,500

Copyright (C) 2006, 2009, 2019, 2020 Donald L. Klipstein.

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