Reality lightning question

XoechZ

Hello!

Now that I am using Reality/Lux, I want to try to light my scenes as it is done in real life photo studios.

What I have found out is that most real studio lights are flash lights. They have an adjustment light (100W, or 200W or just 50W), but they are also connected to the camera and the actual light when the photo is taken, is a flash coming from this light.

I have also found out that a typical camera setting for a studio shot is ISO 100, f8, 1/125.

When I use a mesh light (as a softbox) with 100W and use the above camera settings in Lux, the image is just dark. The light is not visible and I have to turn up the gain to about 200 to get it right.

So, I want to know: How strong is the flash from a real life studio light (e.g. a 100W one)? How do I have to adjust a mesh light in Reality, so that it is as strong as a real studio light? Raise the Watts or the efficiency? Or is it ok do push the light gain so high in Lux?

I hope you know what I mean and I hope that someone can help me here to create "real life" studio lightning.

Thanks in advance!

XoechZ

No one?

Hiro Protagonist

I've been using Luxrender since Reality first came out and I think I get pretty good lighting results, but I don't take any notice of watts or efficiency in lighting values—I simply use gain to set intensities. Similarly, I ignore what should be a realistic camera exposure setting and I generally adjust expose with the ISO value. So I will typically turn on Exposure control in Reality (this sets the tonemapper to Linear, which is highly recommended or even essential). The default camera settings in Reality, when Exposure control is first turned on, are 100, 1/125, F4. For my current lighting set ups I find that too low so I will set ISO to around 250, just as a starting point. I leave all lights at default settings initially.

When I call Luxrender, I will adjust ISO to get a reasonable exposure to begin with then look at the lighting tab. I almost always use IBL with one or two  meshlights, and generally I have to turn up the gain of the meshes (I hardly ever touch the IBL gain). So basically I'm controlling lights and exposure with one only parameter each (gain and ISO) ignoring what might be real world settings. I've never found any benefit in my kind of work to adhereing to realistic camera or light settings. For example, setting a small aperture doesn't increase depth of field as it does in a real camera, high ISO does not make images more grainy as it would with a real film, and shutter speed doesn't have the effect of freezing motion (because their isn't any), so I don't see the point.

As for the intensity of meshlights, you can make these brighter and with sharper shadows by reducing their dimensions (this does model real world behaviour).

You shouldn't need to put a light gain up to anything like 200 though. This sounds like you have the exposure too low. Raise the exposure (e.g. ISO) to get the scene properly exposed before you start changing light gains, and never mind if they are impossible settings in the real world. You can also use Estimate Settings when using the Linear kernel to get a reasonable starting point. The gain of the lights should really just be for balancing the lights against each other rather than for flooding the scene with light—you will not get good results with the latter approach.

XoechZ

Well, lightning is the most important factor of a render. It can make or break the image. No matter how realistic your textures look, no matter how long you fiddle around with skin settings or hair props. In the end, when the light is not good, the image will be not good.

As PB render engines like Lux or Iray try to behave like the real world, it seems logical to me to use real world settings. At least, I want to try it and see if it makes a difference.

You are right about aperture and DOF, but there is a trick to make it real also. No, not a trick, just a setting. Look at the attached image. Enable DOF in Reality and set the f/stop to the same value as you have set it on the camera. There you have it. Aperture DOF like in real life.