- [Tutor] Among the most essential properties of any light
are its intensity and color.
We'll set those up for this photometric light,
select the light and in the modify panel,
we'll see a section labeled intensity color attenuation.
Intensity can be measured using different systems of units.
The default is candelas
that's what's shown here with the abbreviation CD,
and we've got 1500 candelas by default.
We can also choose lumens which is LM,
or lux at, which is abbreviated LX AT.
Most people are familiar with lumens
because that's how light bulbs are rated.
When you buy a light bulb in the store it's rated in lumens.
So let's switch this over to lumens
and we see a value of almost 19,000 lumens.
Well, for a point of reference,
an incandescent light bulb with a 75 wat power load
is going to produce about out 1500 lumens,
not 19,000 but 1500.
Let's try typing that in here,
put in a value of 1500 and press Enter,
and we get an extremely dim shot in our view port.
So we're not putting out very much light
but this is a physically plausible value for illumination.
It's just that we have not yet set up exposure control
to adjust the sensitivity of the camera.
We'll come back to that in the next movie.
For now we'll use a physically implausible intensity
just so we can get familiar
with the features of the photometric light.
I'll increase the lumens value up to 100,000
and press Enter.
And now we've got a pretty good range
of tones in our view port rendering.
Lumens are intuitive but the native units
in max are candelas.
And that's what you'll see in various locations
in the interface such as the light explorer window.
So it's probably better to work in candelas if possible.
Let's switch over to candelas
by clicking on the radio button that says CD,
and the light hasn't changed intensity,
this numeric field value has changed,
the conversion of units is made automatically.
We see that 100,000 lumens equate to about 8,000 candelas.
I also want to demonstrate how to control
the intensity based on distance away from the light.
We do that by enabling the option lux at.
And this spinner field now becomes available,
that has a current value of one meter,
it sets the radius for the light
and I can increase or decrease that.
And as I increase it, we see we get more illumination
because the value here is the amount of incident light
at the distance we specify.
So we can use this to hopefully avoid
the situation of hotspots like this.
We can set a distance, let's say two meters,
and then we can change the incident light value
bring that down and actually I'm going to need
to bring it down to quite a low value, maybe around 2000.
And we've now eliminated that problem of the hotspot there.
So we know exactly how much light
is landing at exactly two meters away.
If we switch the intensity units back to candelas,
we see a nice round number of 8,000.
That's actually a hint that there is a direct relationship
between the output in candelas
and the lux at a certain distance.
All photometric lights in max obey the inverse square law,
also known as quadratic decay.
The energy of the light, it's apparent brightness
will diminish according to the inverse
of the square of the distance.
Okay, then we come to color.
This is important for a realistic architectural rendering
especially in a situation of mixed lighting
such as combined natural and artificial light.
Up here in the color section,
we can choose is a lighting preset from this pull down list,
or we can set the color manually in degrees Kelvin,
or we can plug in an RGB value in this filter color swatch.
Let's choose a preset first.
We can see that the default is D65.
D65 illuminate reference white
corresponds to pure white on a computer monitor.
So if we had a white object in our scene
it would render as white on our screen
if we have the D65 illuminate preset chosen.
Let's try something else such as fluorescent, warm white.
And now we see our view port light
is considerably more orange.
I actually prefer to set the Kelvin value manually
because I'll know exactly what I'm getting.
When I choose one of these presets,
I don't actually know what the Kelvin value
of that preset is.
I'll choose Kelvin and if I wanted this to be less orange,
then I could increase the Kelvin value in degrees,
maybe bring that up to a value of 4,800 degrees,
and now we've got a less orange and more blue rendering.
It's important to note at this point
that we also have the ability
to set the color temperature or white balance
for the camera in the exposure control settings.
So for example we can white balance the camera
to find a compromise between the blue color
of indirect natural skylight coming in through a window
and the orange color of artificial lighting.
We'll take a look at exposure control
in the following movie.
For theatrical lighting effects,
you can use the filter color
and set that to a particular RGB value.
Now filter color is a multiplier for the base color
which we can choose up here
with a preset or with a Kelvin value.
I don't actually want to mix these two things.
I want the illumination to exactly match
the RGB values I choose in the filter color.
So I'll set the base color back to a preset
which is the default D65 aluminum reference white.
Now, whatever I choose in my filter color
will be the color of the light
and it won't mix with the base color.
So I'll click on that color swatch
and then plug in some value,
we'll need some saturation and change up the hue
and we can get some interesting lighting effect in our view.
All right, so that's pretty cool,
we've got an interesting artistic effect.
Unfortunately, the values in that dialogue are eight bit,
they only range from zero to 255,
but we can still get pretty good artistic effects
in our rendering.
Okay, we can go back to neutral D65 white
by clicking on that filter color
and bringing the saturation back down to zero.
If saturation to zero and value is 255,
then we're not introducing any filter at all.
That's how to set up the intensity
and color for a photometric light.