pacorosso

Great Barry, I add it to my bookmarks (I work in the same, publish writes about lighting in my web and in magazines).

Thanks to all, I go on in the looking for the names.

It's up of your way to understand the scene. I always have a gossen in my bag. Is the only way to measure the ratios and the vertical/horizontal ratio of light BEFORE tell the model to stay under the ligth.

With the photometer I can mark the space where the model can move, I can know previously to the shoot if I will have a good vertical/horizontal ratio (which is the secret to a good face and skin rendering). With the camera I only can do such things by the "trial and error" method. And this is not a way for me. I like to know what I do, not to do what I know.

If you can read spanish my book lightning is: "T飮icas de iluminaci�n en fotografí¡ y cinematografí¡¢ edited by Omega in Barcelona.

 

A first electronic edition (a previous release to the final version on paper) is here (for free):

 

http://pacorosso.5gbfree.com/pacorosso/tec/pdf/el1.pdf

 

In my web there is a lot of pdf about lighting (in spanish):

 

www.pacorosso.com

never more than 45 grades. Because that is the slope of the eyelid. Greater grades make a shade skin tone.

Put the dome and make a incident read. Aime the dome:

1 To the camera.

2 To the main light.

 

If the difference is greater than 1,5 stops then you can have a specular bright if the main light is too "lateral".

Otherwise expose for the camera measure.

Last wednesday I shoot these photographies and, when downloading it I see what I was doing...

 

Believe me. I did not realize what I was shooting until I see it in the computer...

 

http://1photobyday.blogspot.com/2007/02/maestros.html

 

The text say (in spanish):

 

A master is somebody who teach you without you know he is teaching and, after a time, you find yourself refecting what you learned without realize it.

When metering mixed lights you can make forget about th eambient light when it is 3 stops lower than that of your flashes with this restrictions:

 

1) The ambient light has a color rendering similar to that of your flashes (Color rendering is not only the "colour temperature" but too the Color Reproduction Index).

2) The ambient light should not illuminate the "shades" part of the figure. Or at least, the ambient light do must be at least 3 stops under the rest of your lights.

 

When metering mixed lights (ambient plus flash) you can estimate the amount of flash supplied in this way:

 

Read the f for the ambient light at the synchro time you are going to use.

Read the f of the flash.

 

Now write the difference beetween in terms of light ratio. The actual ratio beetween the ("bare") flash and the ambient is that ratio minus 1.

 

For bounced lights you can estimate so the change to make in the power of the flash units to achieve the f number you want.

For a point source you can calculate so:

The fall of light when you change the distance is:

 

d=2^(n/2)

 

Where d is the distance from the light source to the scene.

n is the number of stops the lights fall.

 

The inmediate consecuence is the guide number. The f number you get at a reference distance:

 

f=G/d

 

For fine adjustment you can remember this:

 

To increase th eligh you should put your lights far away:

STOPS FAR

1/3 11%

1/2 16%

2/3 21%

 

To reduce, close the lights:

 

STOPS CLOSE

1/3 12%

1/2 19%

2/3 26%

 

This is given in %. So if you use a metric system the number gets you the amount of centimeters you should move your lights to correct the illumination for each meter of distance.

 

For example, if your light are a 3,5 meters and wnat increase the illumination in 1/2 stop you should close the lamps 19 centimeters for each meter. It is: 19+19+19+9.5 = 66,5 centimeter.

�how is the background? When shooting on open flash we must be aware of the lights in the background and the lights part of the model as she move. I think you don have to worry about the reciprocity for the 15 seconds, you do not try to expose the back (I think).

?To fill with a manual mode flash? It's easy! I have been writing about this procedure over years (My first article in november of the year 1994).

 

Let's go:

 

You have a dark figure over a light background (Sunset, dark street with a light place backwards, an indoor shoot with open windows, etc)

 

First, read the f number for the figure.

Second read the f number for the background.

 

-If the difference is 1 stop adjust your flash so it gives you the same f number you read in the figure.

-If the difference is 2 stops, adjusto your flash so it gives you one and a half f greeater that that of the figure.

-If the difference is 3 or greater, adjust the f number of the flash at the same f number of the background.

 

When I say "f number of the background" I mean "The f number YOU WNAT TO USE for the backgorund, not the f you read. This is because maybe you want the background will be a little more "light" than it is. What is waht we see usually.

 

Two stops under the figure is a verly low amount of light. The f number you should use for the flash is beetween the f of the figure and the fo for the background.

 

Of course the f you adjust in your camera is that of the background.

 

?How to adjust the f number in a manual flash? Three ways:

 

First: Use its guide number to change the distance.

Second: If your can flash can do it, use the power adjustement of your unit (My prefer, with a Sumpan 3600 which can be adjusted until 1/32 of power).

Third: use diffuser.

 

More on this is:

-How to fill a figure with a side lighet who produce too much contraste (for example, a figure near a window).

-How to fill the same figure near the window but when you want not only control the contrast in her face, but to expose correctly the outdoor view from th ewindow.

-how to do it with a manual flash bounced in the ceil.

The power in W only talks about the capacity to produce the ligth, but with a certain amunto of light you can get many differents exposures only changig its distribution. The reflector you use affects to the exposure you get more than the power of the generator.

First.

?Why do you think the gray of your printer is neutral? It seems to your gaze but you know we adjust the neutral to the "lost neutral thing" you can see in that exact moment.

 

Second ?How to get a 18%? Well theorycally filla image with a r=g=b=116 value. That is a 18% medium gray. If you have a good connfiguration of your color management system, it works.

 

BUT:

sincerely, it is easeier: Take what ever you want wich is gray, borrow a medium gray card and read the difference in stops beetween the gray 18% and the gray you have selected. Use always that "(non medium)gray card" with a "corection" of the difference value you read.

You can use the gray card to verify the calibration of the photometer of the camera, for example to know how precise is the TTL system.

 

The test will say you the actual sensitivity of the combination camera-photometer/flash/film.

 

With digital, actually you know the sensitivity of your digital camera with that flash.

 

For this, shoot several photos of the card in your authomatic-preferred mode. Open the image and, if it is in sRGB or AdobeRGB the gray should by around 117 in the image with the correct sensititvity. Once you know this, set that ISO speed in the flash.

(You can have a 1 value of diference, it is R=G=B=116. Or 117. Or 118).

"1) Why do some manufacturers rate the Guide number on their "on-camera' flash based on the focal length of the lens. For example, Canon rates the Guide Number for their 550EX flash as 180 "with a 105mm lens"."

 

That lenses are not that of the camera, but that of the flash. You are right, number guide is the same for a 28mm than for a 50 than for a 135 IF YOU DO NOT "ZOOM" THE FLASH. Almost all the modern flashes do a zoom tracking the focal lens you mount. So, at last, with this authomatic modes the flash is "controled" by the lenses, and the manufacturer can take the liberty to say "number guide for a lens".

 

But it is incorrect, as you say. The number guide relais upon the zoom of the flash.

 

"2) Another thing that got me fidgety is Watts seconds. Watts seconds is the measurement used for most studio flash and some on-camera flash units. So how does Watts-second relate to guide numbers ?"

 

Wats per seconds is Jules. The international unit for energy. What the flash say is the amount of electrical energy which can store.

Now think in this way: you have a 400 watts. Thats mean the lamps can give 400 wats in 1 second.

Or 800 in 1/2.

Or 1600 in 1/4...

﾿What is the emission time of that flash?

Think in this, That's the rease why little units can give so much amount of light.

A f:45 guide number flash with a 1/350 second emission time (a metz 45CL2) gives almost 2.000.000 luxes at a distance of 1 meter. The sun, in his betterdays produce 100.000. 20 times less that a little flash.

 

 

" Can you use watt seconds to determine the correct F stop, or distance-to-subject ? What exactly do they mean by watts seconds. "

 

No. At least, not easily. The amount of light depends upon the reflector you use. Think in this: if you set the lamp without reflector (bare lamp) it emits light in all directions (an sphere). If you set a mirror behind the lamp then you get an hemisphere: the whole amount the light distributed ("compressed") in the half space. So you multiply per 2 the number guide. If you set a reflector which "close" the emission angle you achieve a proportional rise of the guide number.

 

One way to calculate the guide number is if you know the rendition of the lamp. If you have, for example, a lamp with 100 lumens per watt per second, you can know the total amount of lumens emited (dividing one and one the wats per second as I did before). From the total lumens emitted you can calculate the intensity of light (candles) dividing the lumens value by the angle of emission. You have the data of the horizontal and vertical angles in the brochure of the reflector, with this two data you can easily calculate the "solid angle" which is the number you need to know to divide the lumens for. The result is the lux you get a 1 meter. 1000 lux are 1/50 at f:2.8 and ISO 100/21.

 

Another way is to know the BCPS or the ECPS. This is the total light emision and is pair lamp-reflector.

 

The guide number with the BCPS data is:

 

GN = 0.15 squareroot(BCPS * ISO)

 

Where ISO is the old ASA number of the ISO speed.

I think 110 watts is too little. �What is the size of your original? Think you need a good f number to achieve enough deep of field

File not found

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I think it is preferable to set all up but covering with your hand the light coming from other sources you do not want no meter. Doing so you can meter the light coming from the direction of the flash you want to meter. It is: if you switch off all the lights (except the one you want to read) then it only comes in consideration the light emited by that flash. This is give yu a false idea of what is happenig in the scene. When you swithh on all the lights, and cover with your hand, then it comes not in consideration the straight light coming from the other sources, but you can read so the bounced light and the way the enviroment affects the scene.

M stands for manual. It is full power.

�How do yo say? CRI IS the metric. I have years telling this. Color temperature has nothing to do with fluorescent or discharge lamps. CRI IS the metric to use.

 

For photography you can be confident in this: if CRI is greater than 80 you can render a good color reproduction in your photos

BUT...

 

CRI do not means that you do not have color cast. Maybe that is what you have heard. You can have a high CRI and color cast. But the question is this: if you have a high CRI then you always can FILTER the light.

 

For example. You have a fluorescent with a CRI 70 and a color temperature 4200. Supoonse you have inyour images a green cast (for example). As you have a lower CRI YOU CANNOT compensate the color cast. If you use a magenta gel you will turn dark and dirty your colors.

Now you have the same color cast, the same color temperature but with a CRI 90. Then you can filter with a magenta gel and recover the color your eyes seen.

There is a lamp in the top of the model. You can see the hard shace under her nose. The degradation tone can be due a short distance beetwee the lamp and the face. Or for a postprocessing tool.

I do not understand completely thequestion �What do you mean when say "the same amount of light"? The exposure depends on the luminance of the scene. And the subject you are photographing does not change its luminance when you slect a narrow angle of vision.

On the other hand, there is differences in the way two diferents lenses capture the light. You can be confident in a number f lets pass through the same amount of light in a wide angle than in a telephoto. Of course there is differences, for example when shooting at very short or very long distances.

But it has a shadow in the middle of the figure, this is caused by a two sided lights. As the figure is not facing the camera I think the two "fronted" ligths are one at the right of the photographer and the other almost a counterlight (maybe you could call it "a kicker" more than a counterlight). The degradation of the light in the length of the figure sugest me a featherd light as the transition zone from the light to the shadow that a fresnel render.

I supose it has a fresnel with soft decay or a honeycomb at the right of the image and a counterlight at the left.

Early in the morning. Never at midday.

And, with the sun at your side. In the same line than your shoulders.