Answers.Body: <p>You could do some back of the envelope calculations, if they're both the same shape and the LEDs in them have similar lenses etc., the beam will be similar, so the falloff will be similar.</p>
  <p>Given that the area illuminated at 1m is 4 times the area illuminated at 0.5m (area of a segment of a sphere is proportional to the radius squared, so twice the distance squared is 4 times the area), the intensity of the first is going to be roughly ¼ that of the second. Which figures, going by the model number: the first is probably meant to be &quot;equivalent&quot; (these figures are always rubbery) to a 260W incandescent light and the second to a 1000W light, so roughly 4 times as powerful.</p>
  <p>You could also compare the wattage to see exactly how much power each one is.</p>
  <p>In cases where they're not similar size and distribution (BTW the first panel is less than half of the area of the second, so in no way would I say they're similar in size), then you're comparing apples with oranges. Different lights do different jobs.</p>
  <p>TBH With cheapo lights like that I'd actually be more concerned about how good the colour was.</p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2021-03-09T10:19:49.133Z
Answers.Text: This is helpful, but does not completely solve my problem. You seem to be able to estimate the tunsgen equivalent of the lights I listed. I am looking for some way to do that too. Ultimately, I need some starting point so that I can know what I'm dealing with, even if very approximate. Thanks!
Answers.UserDisplayName: Dwarf Vader
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2021-03-10T02:07:05.577Z
Answers.Text: I'm going off the model number. Many LED manufacturers base their lights on tungsten equivalents, in order to help users switch. They always inflate the values though, so use caution. Find out how much power (will be given in Watts) the LEDs use and that will give you an idea of their output. Rule of thumb is multiply it by 4 to get the equivalent for a tungsten globe. So a 100W LED is about the same as a 400W tungsten.
Answers.UserDisplayName: stib
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2021-03-10T11:15:21.090Z
Answers.Text: Thanks. So in this case, the P260C consumes 30W, and the 1000Bi II consumes 70W. So although the model names might hint that they'd be ~300W and ~1000W equivalents, the truth is they could very well be closer to 120W and 280W respectively. From experience, I would say that the P260C is somewhere in-between those two values.
Answers.UserDisplayName: Dwarf Vader
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2021-03-11T19:23:22.253Z
Answers.Text: Some lighting manufacturers publish photometric data of their lights as .ies files. This is usually for architectural applications, but you could look for lights with similar specifications, and compare their .ies profiles in a 3D package that supports PBR.
Answers.UserDisplayName: Jason Conrad
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2021-03-04T22:19:23.340Z
Answers.LastActivityDate: 2021-03-04T22:27:36.047Z
Answers.LastEditDate: 2021-03-04T22:27:36.047Z
Answers.UserDisplayName: stib
Body: <p>I am trying to compare the brightness of these two fixtures:</p>
  <blockquote>
  <p>Godox LEDP260C: 2050 Lux @ 0.5m</p>
  </blockquote>
  <blockquote>
  <p>Godox LED1000Bi II: 2200 Lux @ 1m</p>
  </blockquote>
  <p>(Both at 3300K).</p>
  <p>How do I effectively compare these two values? The light sources are similar in shape and size (30x20cm for the first and 40x40cm for the second).</p>
  <p>How. Do I go about comparing these two? What about cases where the size and distribution of light is not so similar?</p>
  
Tags: <lighting>
Title: How to compare the illuminance of similar light fixtures in Lux given at different distances?
UserDisplayName: Dwarf Vader
ThreadText: # How to compare the illuminance of similar light fixtures in Lux given at different distances?
  
  (Asked by: username_0 on 2021-03-04)
  
  I am trying to compare the brightness of these two fixtures:
  
  > Godox LEDP260C: 2050 Lux @ 0.5m
  
  > Godox LED1000Bi II: 2200 Lux @ 1m
  
  (Both at 3300K).
  
  How do I effectively compare these two values? The light sources are similar in shape and size (30x20cm for the first and 40x40cm for the second).
  
  How. Do I go about comparing these two? What about cases where the size and distribution of light is not so similar?
  
  **Tags:** lighting
  
  
  ---
  
  ## 1 answers
  
  ### Answer by username_1 on 2021-03-04. Score: 2 | Accepted answer
  
  You could do some back of the envelope calculations, if they're both the same shape and the LEDs in them have similar lenses etc., the beam will be similar, so the falloff will be similar.
  
  Given that the area illuminated at 1m is 4 times the area illuminated at 0.5m (area of a segment of a sphere is proportional to the radius squared, so twice the distance squared is 4 times the area), the intensity of the first is going to be roughly ¼ that of the second. Which figures, going by the model number: the first is probably meant to be "equivalent" (these figures are always rubbery) to a 260W incandescent light and the second to a 1000W light, so roughly 4 times as powerful.
  
  You could also compare the wattage to see exactly how much power each one is.
  
  In cases where they're not similar size and distribution (BTW the first panel is less than half of the area of the second, so in no way would I say they're similar in size), then you're comparing apples with oranges. Different lights do different jobs.
  
  TBH With cheapo lights like that I'd actually be more concerned about how good the colour was.
  
  > **Comments:**
  > **username_0**: This is helpful, but does not completely solve my problem. You seem to be able to estimate the tunsgen equivalent of the lights I listed. I am looking for some way to do that too. Ultimately, I need some starting point so that I can know what I'm dealing with, even if very approximate. Thanks!  
  > **username_1**: I'm going off the model number. Many LED manufacturers base their lights on tungsten equivalents, in order to help users switch. They always inflate the values though, so use caution. Find out how much power (will be given in Watts) the LEDs use and that will give you an idea of their output. Rule of thumb is multiply it by 4 to get the equivalent for a tungsten globe. So a 100W LED is about the same as a 400W tungsten.  
  > **username_0**: Thanks. So in this case, the P260C consumes 30W, and the 1000Bi II consumes 70W. So although the model names might hint that they'd be ~300W and ~1000W equivalents, the truth is they could very well be closer to 120W and 280W respectively. From experience, I would say that the P260C is somewhere in-between those two values.  
  > **username_2**: Some lighting manufacturers publish photometric data of their lights as .ies files. This is usually for architectural applications, but you could look for lights with similar specifications, and compare their .ies profiles in a 3D package that supports PBR.  
  
  ---
  
  