"tony cooper" <tony_cooper213@[EMAIL PROTECTED]
> wrote in message
news:kof504ht84kg35vqqc5gitnqt7vci2qu7q@[EMAIL PROTECTED]
> On Mon, 14 Apr 2008 01:56:21 GMT, "Dudley Hanks"
> <hanks.dudley@[EMAIL PROTECTED]
> wrote:
>
>>
>>"Paul Furman" <paul-@[EMAIL PROTECTED]
> wrote in message
>>news:oSxMj.3509$vF.2071@[EMAIL PROTECTED]
>>> tony cooper wrote:
>>>
>>>>>>>>> skippy-007@[EMAIL PROTECTED]
quotes...
>>>>>>>>>> The camera plane is a horizontal line that runs
>>>>>>>>>> directly across the camera position as it relates to the
positon
>>>>>>>>>> of
>>>>>>>>>> the
>>>>>>>>>> subject.
>>>>
>>>> In the sentence quoted, it's perfectly clear
>>>> that the plane is being extended in the form of a line.
>>>
>>> It is unclear without knowing if we are looking at a side view or top
>>> view. The sentence only describes a line not a plane. The only plane
>>> that
>>> makes sense would be the film plane or sensor which is perpendicular
to
>>> the line connecting the camera & subject. Or maybe it's the plane that
>>> meets the horizon? No way to know.
>>>
>>> This next part seems unrelated but suggests it's a discussion of the
>>> line
>>> connecting the camera & subject:
>>>
>>> >>>>>>> The subject is at the center of a circle and the camera
>>> >>>>>>> is at the outside edge of the circle so we are able to move
>>> >>>>>>> lights around an invisible circle at different degrees
>>
>>The way I read it, the OP is looking at a plane -- similar to the film
>>plane -- which extends around the subject in a circle.
>
> I don't think so. The plane is perpendicular to the axis of the
> camera lens.
>
I realize this is stretching things a bit, but, if one took a limited
slice
of the focal plane and then rotated it around the subject while
maintaining
the subject to camera distance, the "plane" would circumscribe a circle at
a
given radius. This is what I imagined the quote to be referring to.
Having
not sat in a geometry class for quite some time, my use of these terms can
get fairly fuzzy. But, if one adopts this perspective, the bit about the
lights moving around the circle makes sense in the scenario I described.
>> If one were to place
>>lights, either flash or floodlights, on that plane,
around that cylinder?
one could maintain a
>>given lighting ratio while shifting the lights around the subject.
>
> The lights would be placed in an arc with the center point of the arc
> being where the plane intersects with the camera lens axis.
That's what I wanted to say...
>
> I don't know whether or not that is a valid technique of lighting. It
> seems to be something the OP has read, but there's not enough quoted
> to take a guess about the validity of it.
Admittedly, I was reading a bit into the quote, but it's the only way I
can
make sense of the details given.
>
> When doing macro shooting straight at the subject horizontally, I do
> position the lights in a rough arc around the axis of the camera lens,
> but I certainly don't try to calculate how exactly they are placed.
If my interpretation is correct, that would be the point. If you
circumscribe a line around a center spot, and if your lights are mounted
on
rolling stands, then your fill light, key light and any other auxilarry
lights could be shifted around the outside of the circle without messing
up
the lighting ratio.
I'm sure Ken will attest that lighting ratios for portraits are calculated
very accurately and usually expressed in a ratio of the intensity of the
key
light to the fill light. 2:1, 3:1 and 4:1 being typical ratios. The
higher
the ratio, the more dramatic the lighting.
However, men tend to look better with side-lit, higher contrast lighting
than women -- which tend to look better with a more glamorous, softer
placement of the lights. Using the circular movement described, one could
move the key light farther away from the camera to light men more from the
side (producing more visible shadows on the far side), and back closer to
the camera again for women (reducing the shadow on the far side.
Regardless of the placement, though, the overall exposure should remain
relatively constant because the distance to the lights remains constant.
Thus, no calculations.
>
> In most of the macro work that I do, I shoot straight down on the
> subject using a tripod. The lights are positioned equidistant from
> the focal plane (because both the camera's position and the light
> positions are fixed), but my lights are in a full circle and not an
> arc.
But, in macro work, you generally try to eliminate most shadows. In
portraiture, you want to incorporate them in order to accentuate
desireable
features, and to detract from less desirable ones, or simply to help
achieve
a cirtain ambiance. Am I right, Ken? So, different approaches are used.
>
>> One
>>could then vary the effect without altering the exposure as long as the
>>subject to lights / camera remains constant.
>>
>>This could be useful if one wanted to quickly change from a side lit
shot
>>to
>>a more frontal exposure. One would merely move the lights but not have
to
>>alter the exposure settings.
>>
>>I've seen this discussed in a few books I've read on the subject of
studio
>>lighting, but there is usually a cautionary note that, as one shifts the
>>lights, new highlights can pop up and throw off the exposure setting --
>>effectively defeating the careful planning and meticulous work. Of
>>course,
>>eventually, one would gain enough experience to predict this anomaly,
and
>>it
>>should prove to be a good way to organize a portrait studio where one
>>shoots
>>more than one style of portrait.
Doing concert photography, one generally adheres to this type of
technique,
but the lights are fixed, and the subject moves around instead. "In the
old
days," one could determine an exposure setting for a certain distance from
the major light sources, and then try to snap pics when the artists were
at
the desired distance from one of those main lights. It took a bit of
practice, but it would help to increase the number of keepers if one could
master the theory.
>>
>>Take Care,
Dudley
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