I have read bit about studio formulas for lighting like 1:2:4, 1:3:5 (main, fill, ambient) to gain normal portrait lighting or say gothic lighting. Can the BBLight meter(s) be used with the zone system (en.wikipedia.org/wiki/Zone_system ) to achieve these goals? Can the prop be modified to show when the light is in each of these ranges? And would it even make sense to do this with poser?

I'm not familiar with the studio formula lighting idea. By that is it meant that the ratio of light intensities is specific instead of eyeballed?

How does falloff distance come into play with the formula lighting idea?

And did you mean (main=1,fill=2,ambient=4)? That seems odd.

The meter measures illumination from light sources. Unless you enable IDL, the amount of light or luminance from an object in the scene is not included in that measurement.

Real light meters when held close to an object measure the perceived luminance of that object. If the object is dark, this can be very low even in the presence of strong lighting. If the object is white (like snow), it can be very high even in the presence of weak lighting.

The light meter measures the lighting intensity (illumination), not the object luminance (reflected light). 

It would be possible to measure the object luminance, but only if IDL is enabled and you point the meter at the object and swing your camera around so you can see the meter.

Having said that, the meter could be modified to measure and report luminance using the zone system, although that would get into an interesting problem of visual representation. Ideally, the meter would display a zone number. It would be possible to do so with a suitably arranged image with the roman numerals on it. Also the shape of the meter should be flat and use a Clay node as the sensor, instead of a Diffuse node, so that it can more consistently measure the luminance independant of angle of incidence.

It was explained here www.faeriewylde.com/forum2/viewtopic.php  . And to be honest I never really totaly grasped it, and was hopping you did.

Measurement described here uses a spot meter/narrow angle internal meter and an 18% reflective gray card  (rather than an incidence meter).  The ratios are exponential of the base of 2 (think binary) at the point of the subject, perpendicular to the lighting.  The ratios are often achieved with setting the distance from the subject.

1 2 4 is pretty much the standard portrait setting.  1 is the key light, the brightest.  2 is the fill and should read one f/stop dimmer.  4, the shadow fill, should be three f/stops dimmer.  In a standard range, 6 is solid black shadow, ambience too low to show detail.  This is reserved for dramatic effects and is generally shunned for most purposes.

1 3 5 is 2 and 4 f/stops difference in light reflected from the gray card.  There is less contrast, and it's a bit darker in the shadows than a 1 2 4.  1 2 5 will deliver a primary contrast as a 1 2 4, but the shadows will be deeper.

Many studios only worry about key to fill and express ratios 2:1 or 3:1, and let the shadow levels find their own with the bounce of the room as ambient.  But for changing environments, it's better to specify the shadow fill.

Google "studio lighting ratios" if you want more info, though most of it doesn't adhere to a zone system, since most use incidence meters in their examples.

Quote - 1 2 4 is pretty much the standard portrait setting.  1 is the key light, the brightest.  2 is the fill and should read one f/stop dimmer.  4, the shadow fill, should be three f/stops dimmer.

That isn't an accurate statement, if the numbers 1 2 4 represent inverse ratios.

If you're saying the key light luminance is 1, and the fill light luminance is 2 (i.e. 1/2), then the fill light is indeed one stop darker.

But 4 is two stops from 1, not three.

Anyway... let's take a simpler case of just two white lights - an infinite, and an IBL. Suppose you want the brightest part of the surfaces lit by both to be 4 times as bright as the parts where the infinite does not reach. (Assuming the various surfaces have the same reflectivity.)

So you have some that are lit by Inf+IBL, and others that are only lit by the IBL.

You seek:

(Inf+IBL) / IBL = 4

Simple algebra says:

Inf+IBL = 4 * IBL
Inf = 3 * IBL

So - it's simple. Set your infinite light intensity to 3 times that of the IBL. The resulting ratio will always be 4 to 1.

Of course, we're talking about how much light falls on these surfaces, not how much is reflected. How much reflected light you see in the render will depend on the shaders (colors and the math of the various nodes.)

If you're trying to set up a three-light 1:2:4 ratio, things get trickier. If the fill light does not overlap the key light, then it's pretty easy. The fill light should be equal in brightness to the ambient light.

If the key and fill  do overlap, especially if it's a partial overlap as is usually the case, then it's tricky math.

Depending on the overlap, there are situations where the 1:2:4 ratio is simply not possible. This is because an infinite light alone produces a ratio of 1:2 over a curved surface if we compare the incident light at 0 degrees versus 60 degrees off-center. Any additional overlapping light will cause the 60-degree surface to be brighter than 1/2 of the 0 degree surface. So then we're talking about the brightest illumination being somewhere in between pointing at the key light and the fill light. The math is nasty.

I suppose some sort of meter could help find a solution. But I don't have time to work on it right now. I have a work deadline to meet and am going on vacation Friday for a week.