# Photopic/Scotopic



## user4818 (Jan 15, 2009)

Who cares? :yawn: You need to try harder than this.


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## Last Leg (Sep 15, 2011)

Is the Earth round?


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## Cletis (Aug 20, 2010)

*Round*

Well, actually it's not. It's an oblate spheroid


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## user4818 (Jan 15, 2009)

Cletis said:


> Well, actually it's not. It's an oblate spheroid


:nerd:


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## Ima Hack (Aug 31, 2009)

Cletis said:


> Is it real or not ?


Why yes Mr. Cletis it is real.


In lighting design there are two distinct kinds of lumen output produced by lamps. The first is called photopic lumens, which represent the relative sensitivity of the eye under intense lighting such as full outdoor sun. 
Photopic lumen output is the amount of light registered by the cones in the human eye and is measured by standard lumen and footcandle meters.


The second type of lumens are called scotopic, which represent the sensitivity of the eye under typical interior lighting conditions and cannot be measured directly with a standard light meter.
Scotopic lumen output is the amount of light registered by the rods of the human eye and also controls pupil size directly effecting visual acuity for tasks.

:nerd:


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## Cletis (Aug 20, 2010)

*answer*

Great answer Mr. Hack. Would have any idea's on say some made up ratio number to use to transpose photopic to scotopic ??? :icon_wink:


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## Last Leg (Sep 15, 2011)

Cletis said:


> Well, actually it's not. It's an oblate spheroid


Exactly!!!


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## Last Leg (Sep 15, 2011)

I will try to give some data... this is only generalities from trying to figure it out.. some my own gathered stuff.
*TYPE LUMENS**INITIAL LUMENS**SCOTOPIC/PHOTOPIC RATIO**VISUAL EFFECTIVE*1000 W METAL HALIDE110,0001.49163,900 3800K120,0001.6192,000GE LED 12,6002.0425,7045700K12,600225,200VISIONAIRE LED 14,2242.0429,0174000K14,2241.622,758McGRAW LED 12,9512.0426,4204000K12,9511.620,722LED 2700 - 3200K 1.20LED 3200 - 3500K1,5001.42,100LED 3700 - 4700K1,5001.62,400LED 5100 - 5400K1,5001.82,700LED 5900 - 6500K1,50023,000 COMPACT FLUOR 3500K24001.43,360COMPACT FLUOR 5000K 1.970COMPACT FLUOR 6500K 2.190


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## Last Leg (Sep 15, 2011)

Well, that didn't work.


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## Last Leg (Sep 15, 2011)

I'll try once more - these were from one particular site that had the ratios listed, here, as in others you will see the ratios change with the kelvins.
KELVINS
 S/P RATIO
2791​1.2​3065​1.4​3111​1.1​3185​1.1​3398​1.4​3732​1.6​4710​1.6​4716​1.6​5105​1.8​5105​1.8​5149​1.7​5410​1.8​5410​1.8​5738​2​5804​1.9​5912​2​5949​2​6226​2​6345​2​6376​2​6486​2.1​9691​2.3​10757​2.5​13396​2.6​


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## Last Leg (Sep 15, 2011)

Weird - looks fine before I hit submit reply! I give up. Anyway you may be able to make heads and tails out of that one.


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## Cletis (Aug 20, 2010)

*accurate*

Well, that will work for now. You might want to be a little more accurate next time and place ratio out another digit or two, but, that will work. :thumbup:


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## Electric_Light (Apr 6, 2010)

I just wanted to update something here even though the thread is old:

It's seeing more and more acceptance in specifications for very low level lighting such as street lights and generally speaking, higher CCTs have higher S/P ratio. Swap the LPS or 2700K CFL with a 6500K CFL and voila, your scotopic lumen goes up. 

For every other lighting applications, it's not relevant.


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