paco_rosso

<p>a soft light in front of the face and slightly under the nose. (See the shades and the lights in her cheeks).</p>

<p>About the PI factor.<br /><br />When a light beam arrives at a surface can do two things: bounce or splash.<br> The light can bounce as the balls of billiard game. We call this "specular reflection". The light beam comes, and the light beams goes.<br /><br />Now think in a stream of water from a hose pipe against a fence. The stream of water do not "bounce" but "splash. When the light splash we call it "scater" or "diffuse reflection".<br /><br />So, a beam of light (a ray) arrives and change its distribution to a sphere. The change in energy is from a ray to a sphere. This is what the 1/PI factor explain, the change in intensity from the ray of light arriving to the figure to the sphere of light departing from the figure.</p> <p> </p>

<p>The relationship between illuminance and luminance is:<br /><br />L = (r*E)/PI</p> <p>Where L is the luminance, in cd/m2. (Candles per square meter).<br> E is illuminance in lux.<br />r is the reflection coefficient (The ratio between the luminance of a sample of the material divided by the luminance of the reference).<br />PI is PI, it is, 3.141599...</p> <p> </p>

<p>The link you provide to the data says the unit give 3010lx at 1 meter.<br> It is a ISO 100, t:1/60, f: 4.3 at 1 meter from lamp.<br /><br />¿What is the f, t you get with your current lamp?</p>

<p>I shoot dance with a profoto B1. When I set the flash at power 7 (from 10 maximum) I can shoot 4 frames per second. With power set at 6 or 5 I can shoot more framse per second.<br />Other solutions are: profoto B4, broncolor move 1200j, broncolor siros L. All them with batteries.<br> (www.behance.com/pacorosso)</p>

<p>Stop thinking in "incident" and "reflected" reading. Think in "ilumination" and "brillance" reading.<br />The incident what read is the light falling on the stage, it is, the "illumination". If youknow shat amount of light fall on the stage you should not be bored by the place the tones in the gamut: each of the light values fall in his correct place, shades in shades, medium tints in medium tints, lights in tlights.</p>

<p>Stop thinking in "incident" and "reflected" reading. Think in "ilumination" and "brillance" reading.<br />The incident what read is the light falling on the stage, it is, the "illumination". If youknow shat amount of light fall on the stage you should not be bored by the place the tones in the gamut: each of the light values fall in his correct place, shades in shades, medium tints in medium tints, lights in tlights.</p>

<p>I see a big big softbox in front and some high position.<br> And a background ligt, of course.<br />The rim in the face I think is by the reflected light ("reverbered") by the background.</p>

<p>If you wants to sum f numbers:<br> f1 PLUS f2 = sqrt (f1*f1 + f2*f2)</p> <p> </p>

<p>I have some problems with the luminous data of several lamps makers companies.<br /> This table resume the situation: http://pacorossofoto.files.wordpress.com/2013/08/par641.jpg<br> (Commas are used in the way it is used in Europe, as decimal separator, not as thousands, so 11,00 is 11.00 not 11 000).<br /> <img src="http://pacorossofoto.files.wordpress.com/2013/08/par641.jpg" alt="" width="979" height="449" /><br /> The first column "grados" is the plane anle of emmision in degrees. (From catalogue)<br /> Second column is the solid angle, calculated from w = 2 * PI * (1-cos (a/2)) where PI is 3.141599, w is the solid anle in stereorradians and a is the plane angle.<br /><br /><br /> Third column "candela" is the light intensity in candles (data from catalogue). (This lamps are PAR 64).<br /> Fourth column "lumen" is light flux in lumen. It is calculated multiplying the light intensity (3th column) for the solid angle (2nd column) because the light intensity is J = F / w Where F is the flux, J is the intensity and w is the solid angle. This data (flux) is calculated from catalogue data.<br /> Fifth column "W" is the electric power in watts (from catalogue).<br /> Sixth column "R" is the luminous efficacy calculated dividing the lumen (fourth column) over the power (fifth column). R = F / w. It is, R is lumen per watts.<br /> Seventh column is the lamp. OSR stands for Osram, Phil stands for Phillips. The lamps are PAR64 conceived for stage lighting and photographic studio (in wide sense: cinema, TV, etc).</p> <p>My problem... See the R number. About 11lm/w.<br /> In the bibliography it is said the typical R for tungsten is about 25lm/w...<br /><br /><br /> ¿What do you think about it?</p> <p>(If we talk about flash lamps (strobes, not lanterns) the R is as low as 14)<br /><br /><br /> I think I am wrong but do not know where I fail.<br> (Another day we'll talk about why the real BCPS is much lower than the catalogue says).</p>