Headlamp - what type of light?
Taoz
Posts: 10,256
What type of light is the Camera Headlamp actually?
Post edited by Taoz on
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A light of convenience. It is really only meant to light the scene while you are working and there are no other lights.
Yes, but is it a Distant Light, a Spotlight or what ("what" I guess since it doesn't seem to behave like any of the standard lights)?
As far as I am concerned it doesn't matter what type of light it is as you'll always want to add lights to a scene to get good lighting.
Sure, I'm just curious.
It's a good question, actually, and the answer points up why we often suggest not to use it, if you don't have to. It also demonstrates how you can get the same effect, but with more control.
* Distant lights don't have falloff -- the intensity is the same regardless of the depth of the objects in the scene. You'd want to use distant lights for constant sources, like sunlight. A headlamp exhibits depth falloff, therefore a headlamp is not a distant light.
* Spotlights direct their light in a beam fashion, so there is falloff from side to side The source from a headlamp appears to remain constant across the scene, with no gaussian profile. So, probably not a spotlight, either.
* Point lights give off light 360 degrees (unless you use an IES profile with them), and so give a uniform light in any direction. My guess is that the headlamp is closest to a point light. However, the shadows from a headlamp are softer than a default point-emitter point light, suggesting the emitter has a dimension of maybe 3-5cm, or thereabouts.
Things you can control with a headlamp are: ratiometric intensity, plus X, Y, and Z offset. You can't control emitter size, color, or adjust the output photometrically (response related to the human eye).
If you need a light coupled with a camera, and want the "photoflash" look you get with a headlamp, it's better to parent a point light (linear or standard, depending on the effect you want) to the camera, and then adjust the parameters of the light to suit. You can readily set an offset distance from the camera lens, as well as adjust the emitter shape and size in order to control shadows. Keep in mind you need to set the luminous flux value fairly high in order to get an effective light output.
Another benefit is that point lights can accept IES profiles, meaning you can control the shape the light casts into the scene. This provides a nice method for doing very intricate eyelights, for example, of the type popular in older movies, not to mention the original Star Trek TV show.
Headlamp can produce just the right result if you are trying to portray someone taking an amateur flash photo. I am not being sarcastic, either; sometimes that's just what a particular image needs.
It is a Distant Light.
I already explained above why it's not.
How good or bad it is depends on what soemone needs and what their workflow is. I use jsut the headlight camera a lot for composition work. You should not assume that everyone is using DAZ Studio as their primary art tool. It is for me soemtimes, but other times, I use it to generate elements for e.g. a music album or book cover where it is one small component in the final result, and the headlamp can work just fine for that.
I find a headlamp useful primarily when I need a tiny amount of light on a figure in a somewhat gloomy environment or when there's already a lot of direct light. Like, a space ship out amongst stars. I just need to be able to see the ship, not necessarily have a lot of shadows or whatnot.
That said, the vast majority of the time you are better off doing something else.
It IS worth noting that if you are using headlamp and the image looks flat or 'off' or uncompelling, and that matters, to consider shutting it off.
Like argel says, it's handy to have lots of tools in the box for whatever you need.
Which reminds me, is there a way to shut off the headlamp for Perspective and other non-camera modes? I find myself having to set up cameras just so I can see objects lit properly.
Thanks, very useful information!
Yes, I often use it for quick portraits where quality isn't the most important thing, it's a good and easy solution for that IMO.
No, but there's nothing stopping you from creating a set of cameras that you preset or merge in that can be used for various setup chores. I commonly have one set at 90 degrees from the Default camera, and parented. I use that to set up DOF..
Same with a custom headlamp parented to a camera. Just do it once, save the combination, and you can then bring it in whenever you need it. You can really see the benefit of this approach when you use IES profiles. If you're an old film buff, you'll recognize this technique as an Obie.
Sure, and I often have to do that. But when I'm just setting stuff up, it's kind of an extra minor annoyance multiplied a million times. Ah well.
You can save a basic setup, with the cameras, etc, as a scene. Then you can set that scene to be your default when Studio opens. If you are using a scene with included cameras, though, make sure the 'Create Default Camera' option is OFF (unchecked Preferences > Scene) or you will end up with an extra camera.
-Rob
So...it's like the English language...a little of this and pinch of that, with a smattering of something else thrown in, for good measure.
Rob's script returns this:
DzHeadLight inherits DzDistantLight = true
DzHeadLight inherits DzSpotLight = false
DzHeadLight inherits DzPointLight = false
This says that, programatically, the headlamp is based on a distant light. However, it clearly doesn't behave in any way like a distant light, and that's what matters. Without seeing the code, I imagine internally the headlamp starts as a distant light, and then is modified in numerous ways that change its behavior. (Which begs the question, couldn't we also have similar UI controls to similarly change distant light from its single default? Many people have asked for more control over distant lights.)
An assortment of differences:
* A distant light: leaves only stark shadows. The headlamp has softer shadows.
* A distant light has parallel rays from an infinitely distant light source, rather like the sun, so it has no depth falloff. Headlamps clearly have falloff. (I can't decide if the falloff is linear or inverse square -- hard to tell by just looking at test renders.)
* Distant lights are "located" external to the D|S world, so they are outside things like buildings and skydomes, and (in Iray) will not penetrate these things. The headlamp is right there with the camera, and lights the scene even if it's an enclosed interior, or if a skydome is overhead.
As I noted, you can get strikingly similar results with a point light parented to the active camera. With the point light, you then have much more control over the headlamp, which as others have noted in this thread, can come in handy in many types of renders and artistic styles.
You are getting shadows (as distinct from shading) from your headlamp?
Yeah. It helps to have Draw Ground turned on.
Should I not? By default the headlamp appears offset to the left of lens, and slightly above, so there's a shadow cast onto a background slightly down and to the right. The shadow outline is a bit softer than that from a distant light, which is razor hard-edged.
Here are some visual helpers (hope they show; image attaching is being a bit touchy right now). Comparison between headlamp (defaults), distant light (slightly rotated to demonstrate shadowing), and point light (offset similar to headlamp, emitter changed to 4cm disc).
The background is a simple curved plane. Ground shadows is on in all three; for me, I only get the ground shadow with distant lights, not with headlamp or point. Maybe that's just me...
Rob has pointed out that D|S uses the DzDistantLight object as the basis of the headlamp, but I think this demonstrates that whatever properties have been modified from this object, the result you get from a headlamp is the least like a distant light. At least, for Iray, which after all is the default renderer now.
For Iray, yes, there are shadows for the headlamp. For 3DL, no there are not...
3DL
Iray
Thanks!
I also thought it behaved mostly like a distant light, but altered in some way.
Iray or 3DL?
I only use Iray, and I don't see it working at all like a distant light. If Iray is also what you're using, in what ways do you feel it behaves like a distant light? If you refer to my examples of DL, headlamp, and point, it's pretty clear a distant light and the headlamp aren't anything alike.
I'm truly curious how other people are perceiving this, because I get completely different results.
Rob can chime in here, but it seems to me that if the headlamp is designed for 3DL, then there has to be some internal conversion before it can be used with Iray. I'd be interested in what's happening in this conversion.
3DL. It's just my immediate impression, from my experience with the different types of light in 3DL. I rarely use other than the default light in IRay so I don't know what the difference may be here.