Surface Brightness? Tweet

[wisemanxxx]

I can't be sure about surface brightness. For example I use a circular surface for spot light. I set power to 850 lumen and effiency to 0.0014. (viewtopic.php?f=9&t=62045&p=329618&hilit=lumen#p329618) But when I leave surface brightness disabled it is not looking right. Light seems very strong for 850 lumen.Circular Surface' diameter is about 8-10 cm for example.
When I enable surface brightness option it is very dark.
What is the right way for this situation?
I've 3ds max plugin 3.06 4.41.

[paride4331]

Hi wisemanxxx,
it is quite normal to have a very dark scene with 850 lumens, it depends on camera exposure.
Octane camera has not iso and shutter, but we can consider exposure 1 like 100 ISO in outdoor with midday sun.
you should consider shutter too, but let's keep it simple... so with 850 lumens (lightbulb around 60 watts) in a room, I think you should adjust exposure 8.
Regards
Paride

[wisemanxxx]

thank you for your reply. I know I can increase exposure value like a real world camera. My problem is octane light emission's surface brightness option. I can't be sure that I must enable or disable it for a real world light simulation.
When I say "it's very dark" I mean when I compare real world shots with same lumen light sources it doesn't look right.

[paride4331]

Hi wisemanxxx,
correct setting is surface brightness ON.
very dark response, I think right; when you take a shot in real life, your camera increases shutter time.
If you had an analog camera, to shot a room with a 60watt light bulb, you should have about 800 ISO and sutther speed about 1/30s or 1/60s with openings f/5.6.
In Octane f * is for depth of field, but not for brightness; so to get a right shot you need to increase exposure.
Regards
Paride

[wisemanxxx]

Thank you again. Now I'm sure about surface brightness...

[samsue]

Hi wisemanxxx,
correct setting is surface brightness ON.
very dark response, I think right; when you take a shot in real life, your camera increases shutter time.
If you had an analog camera, to shot a room with a 60watt light bulb, you should have about 800 ISO and sutther speed about 1/30s or 1/60s with openings f/5.6.
In Octane f * is for depth of field, but not for brightness; so to get a right shot you need to increase exposure.
Regards
Paride

To get the right light in the octane, we need Wats and Efficiency, the term luminous efficiency can be confused with the term, "luminous efficacy (lm/W)".

1 Is this first statement correct?

Using the example of the projector which is 430w and has an efficiency of 7.3%, which equates to an efficiency of 0.073 in Octane,

2. Do I always have to put two zeros in front of the percentage I find in some tables? Or do you have a specific calculation?

If we only have the value of Lumen, (3. in the original Topic when bepeg4d refers to Lumen it actually meant lm/W right?) we use the calculation lm = W × (lm/W) and we use 0.001464 in the Efficiency float value, which is the result of 1/683.

As most of the time the manufacturer provides Lumen, it is very basic, just use the Lumen Value in Power and 0.001464 in Efficiency.

4. Do you have any conversion to find the % having the values of W and lm/W?

[paride4331]

Hi wisemanxxx,
correct setting is surface brightness ON.
very dark response, I think right; when you take a shot in real life, your camera increases shutter time.
If you had an analog camera, to shot a room with a 60watt light bulb, you should have about 800 ISO and sutther speed about 1/30s or 1/60s with openings f/5.6.
In Octane f * is for depth of field, but not for brightness; so to get a right shot you need to increase exposure.
Regards
Paride

To get the right light in the octane, we need Wats and Efficiency, the term luminous efficiency can be confused with the term, "luminous efficacy (lm/W)".

1 Is this first statement correct?

Using the example of the projector which is 430w and has an efficiency of 7.3%, which equates to an efficiency of 0.073 in Octane,

2. Do I always have to put two zeros in front of the percentage I find in some tables? Or do you have a specific calculation?

If we only have the value of Lumen, (3. in the original Topic when bepeg4d refers to Lumen it actually meant lm/W right?) we use the calculation lm = W × (lm/W) and we use 0.001464 in the Efficiency float value, which is the result of 1/683.

As most of the time the manufacturer provides Lumen, it is very basic, just use the Lumen Value in Power and 0.001464 in Efficiency.

4. Do you have any conversion to find the % having the values of W and lm/W?

Hi samsue,
lumen*[1\631]
put 0,00158478 in texture slot, then lumen value in power.
Regards
Paride

[samsue]

.

[samsue]

Hi wisemanxxx,
correct setting is surface brightness ON.
very dark response, I think right; when you take a shot in real life, your camera increases shutter time.
If you had an analog camera, to shot a room with a 60watt light bulb, you should have about 800 ISO and sutther speed about 1/30s or 1/60s with openings f/5.6.
In Octane f * is for depth of field, but not for brightness; so to get a right shot you need to increase exposure.
Regards
Paride

To get the right light in the octane, we need Wats and Efficiency, the term luminous efficiency can be confused with the term, "luminous efficacy (lm/W)".

1 Is this first statement correct?

Using the example of the projector which is 430w and has an efficiency of 7.3%, which equates to an efficiency of 0.073 in Octane,

2. Do I always have to put two zeros in front of the percentage I find in some tables? Or do you have a specific calculation?

If we only have the value of Lumen, (3. in the original Topic when bepeg4d refers to Lumen it actually meant lm/W right?) we use the calculation lm = W × (lm/W) and we use 0.001464 in the Efficiency float value, which is the result of 1/683.

As most of the time the manufacturer provides Lumen, it is very basic, just use the Lumen Value in Power and 0.001464 in Efficiency.

4. Do you have any conversion to find the % having the values of W and lm/W?

Hi samsue,
lumen*[1\631]
put 0,00158478 in texture slot, then lumen value in power.
Regards
Paride

1. 631 or 683?

"Photopic luminous efficacy of radiation has a maximum possible value of 683 lm/W,!"

2. How it works with normal Octane Lights? You only have Power.


3. on this scene that you have upload, i could not figured out why do you have on Power 60. its the lm/w?

viewtopic.php?f=27&t=64872&p=329709#p329709

[samsue]

Hey,

I've been studying the subject, but it doesn't feel right, turning on the surface bright