Light Output Measurements: Difference between revisions
→Lumens
(→Lux) |
(→Lumens) |
||
| Line 11: | Line 11: | ||
However, a flashlight rarely has consistent output. Instead the output usually drops off early as the LED heats up. So the initial output can be fairly high and then drop by 10-20% within a few minutes. Depending on how well regulated the light is, the output can continue to vary with battery voltage. | However, a flashlight rarely has consistent output. Instead the output usually drops off early as the LED heats up. So the initial output can be fairly high and then drop by 10-20% within a few minutes. Depending on how well regulated the light is, the output can continue to vary with battery voltage. | ||
'''FL-1 lumens''' or '''ANSI lumens''' The [[ANSI-NEMA FL-1|ANSI/NEMA FL-1]] standard requires an integrating sphere and uses a reading taken after the light has been on full power for | '''FL-1 lumens''' or '''ANSI lumens''' The [[ANSI-NEMA FL-1|ANSI/NEMA FL-1]] standard requires an integrating sphere and uses a reading taken after the light has been on full power for 30-120 seconds. This number is even lower than "out the front" lumens. | ||
As an example of how lumens can vary, take the [[4Sevens]] Quark MiNi 123. This flashlight features a Cree XP-G LED with an R5 brightness bin that gives 139 lumens at 350mA. The MiNi probably drives the LED at closer to 1000mA, so the [http://www.cree.com/products/pdf/XLampXP-G.pdf XP-G specs] indicate 250% of the nominal luminous flux or 347.5 lumens at the emitter. However, 4Sevens advertises 189 out-the-front lumens. When [http://www.candlepowerforums.com/vb/showpost.php?p=3296637&postcount=121 bigchelis tested the MiNi 123] with a CR123A primary cell, he got a reading of 142 lumens when the light was turned on and 137 lumens at 3 minutes (with a higher voltage, faster draining IMR cell, MrGman measured 200 lumens at turn-on and 190 lumens at 2 minutes). Later on, 4Sevens introduced a version of this light with a S2 bin XP-G LED which should be 7% brighter. However for this light they used FL-1 testing and advertise only 135 lumens. | As an example of how lumens can vary, take the [[4Sevens]] Quark MiNi 123. This flashlight features a Cree XP-G LED with an R5 brightness bin that gives 139 lumens at 350mA. The MiNi probably drives the LED at closer to 1000mA, so the [http://www.cree.com/products/pdf/XLampXP-G.pdf XP-G specs] indicate 250% of the nominal luminous flux or 347.5 lumens at the emitter. However, 4Sevens advertises 189 out-the-front lumens. When [http://www.candlepowerforums.com/vb/showpost.php?p=3296637&postcount=121 bigchelis tested the MiNi 123] with a CR123A primary cell, he got a reading of 142 lumens when the light was turned on and 137 lumens at 3 minutes (with a higher voltage, faster draining IMR cell, MrGman measured 200 lumens at turn-on and 190 lumens at 2 minutes). Later on, 4Sevens introduced a version of this light with a S2 bin XP-G LED which should be 7% brighter. However for this light they used FL-1 testing and advertise only 135 lumens. | ||