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Fun Cinematography Tricks


The following are fun excercsises and information.


Strange Shutter Angles

Have you ever wondered why some cameras have a shutter setting of 172.8º and 144º?

If you are shooting at 24 FPS in a country that uses 50Hz electricity, the 172.8º shutter angle is used to avoid flicker from fluorescent lights, mercury vapor, metal halide additive types, high pressure sodium light (street lights), CSI, CID, HMI and similar AC arc discharge sources.

If you are shooting at 24 FPS in a country that uses 60Hz electricity, the 144º shutter angle is used to avoid flicker from AC arc discharge sources.

Please note that there are electronic flicker-free ballasts for HMI lights.

Lighting Ratios
Lighting Ratio Difference in
F/T stops
1:1                0
1.25:1                0.25
1.5:1                0.5
1.75:1                0.75
2:1                1
2.5:1                1.25
3:1                1.5
3.5:1                1.75
4:1                2
5:1                2.25
6:1                2.5
7:1                2.75
8:1                3
10:1                3.25
12:1                3.5
14:1                3.75
16:1                4
20:1                4.25
24:1                4.5
28:1                4.75
32:1                5
40:1                5.25
48:1                5.5
56:1                5.75
64:1                6
80:1                6.25
96:1                6.5
112:1                6.75
128:1                7
How to Find Lighting Ratio:

Take a reading so KEY+FILL hits light meter dome. Then take a reading of FILL only. Difference in F-stops gives you lighting ratio.



How to Determine Your Film Camera's Shutter Speed:

Multiply 360 by fps and divide by shutter angle.

fps = frames per second

360 · fps
-------------
shutter angle		 = Shutter Speed


How to Determine Footcandles, Given the "T" Stop of the Lens and EI Rating of the Film:

Divide 1250 by the EI and multiply the result by the Square of the "T" stop.

"T" Stops and their Squares
"T" Stop Square of
"T" Stop
    T 1 1     
    T 1.4 2     
    T 2 4     
    T 2.8 8     
    T 4 16     
    T 5.6 32     
    T 8 64     
    T 11 128     
    T 16 256     
    T 22 512     
Example:

You are shooting film with an EI (exposure index / ASA / ISO number) of 500. You want an F-stop or T-stop of 2.8. You want to know what is the minimum number of footcandles necessary to get a good exposure.

So, 1250 divided by 500 is 2.5 & this multiplied by the square of 2.8 (8) equals 20. (2.5 x 8 = 20) You need 20 footcandles to get a good exposure at T 2.8 using film with EI of 500. (170º shutter angle / 24 fps)

Adapted from Anton Wilson, Cinema Workshop, 4th ed., (A.S.C. Holding, Hollywood), pp.149-150.



If Shooting Film for Video Remember:

Video has a latitude ( luminance ratio ) of maximum 5 Stops ( 32:1. ) 2.5 F-stops under and 2.5 stops over proper exposure. Anything under or over these exposures will not be seen.

Also, always include a white reference and a black reference in each shot. It helps the TV screen to portray correctly the tonal values in the shot. The white reference should not be more than 1 ½ stops brighter than your subject's face.

To assure the results you want in processing and telecine, always expose a gray scale at the head of each new lighting setup. To be effective a gray scale must be illuminated by the key light. When a scene features colored lighting effects, a gray scale must be exposed at the head of the shot, using uncolored light first. Otherwise, the telecine colorist will attempt to "correct" the added color. In lieu of a gray scale, an 18 percent gray card will do. Color chip charts, while eye-catching, are useless for color correcting film to tape.

Based on and quoted directly from Kodak's H-2 publication, Cinematographer's Field Guide, 5th ed., (Eastman Kodak Company, Rochester), pp. 57 and Kodak's H-120 publication, Creating Better Video with 16mm film, (Eastman Kodak Company, Rochester), Chapter 5 under "Exposing a gray scale"


18 Percent Gray Card Information:

When using a medium-grey 18 percent card and reflected light meter, the card should be angled halfway between the light angle and the camera to get the most accurate reading.

From Kris Malkiewicz, Cinematography, 2nd ed., (Simon & Schuster, New York), p. 86.


When Using a Depth of Field Chart Remember:

The hyperfocal distance is a precalculated figure indicating that if the given lens at the given F-stop is focused at this measurement, everything from half this distance to infinity will be in acceptable focus.

From Kris Malkiewicz, Cinematography, 2nd ed., (Simon & Schuster, New York), p. 12.


Useful Rule for Practical Lamps:

The lamp will look convincing if it is approximately 2½ stops brighter than the face. ( The exposure is set for the face. )

Adapted from Kris Malkiewicz, Cinematography, 2 ed., (Simon & Schuster, New York), p. 88.


Color Filter Theory

The color of the object will change when the light falling on it is not white. For example, when a "blue" object is illuminated by light not containing blue wavelengths, the object will appear black.

Yellow is called "minus blue," because a yellow filter stops blue and passes green and red, which together make yellow light.

Magenta is called "minus green," because a magenta filter stops green light and passes blue and red, which together make magenta light.

Cyan is called "minus red," because a cyan filter stops red light and passes blue and green, which together make cyan light.

From Kris Malkiewicz, Cinematography, 2 ed., (Simon & Schuster, New York), pp. 62-64.




RELATIVE LENS FOCAL LENGTH FOR FOUR FORMATS
HORI-
ZONTAL
ANGLE		 35mm STILL
(32mm x 24mm)		 35mm CINE
(24.9mm x
18.67mm)		 16mm CINE
(10.16mm x
7.62mm)		 VIDEO 2/3"
(8.8mm x
6.6mm)
77º 18mm 15mm 5.9mm 5.1mm
61º 24mm 19mm 7.6mm 6.6mm
54º 30mm 25mm 10mm 8.7mm
44º 40mm 30mm 12.5mm 10.8mm
35º 50mm 40mm 16mm 14mm
23º 80mm 60mm 25mm 22mm
12º 160mm 125mm 50mm 43mm
7.8º 235mm 190mm 75mm 65mm
5.8º 320mm 250mm 100mm 87mm
3.8º 470mm 380mm 150mm 130mm
2.9º 640mm 500mm 200mm 175mm
1.9º 950mm 750mm 300mm 260mm
1.2º 1575mm 1250mm 500mm 430mm
0.7º 2500mm 2000mm 800mm 700mm
0.6º 3150mm 2500mm 1000mm 865mm


From Anton Wilson, Cinema Workshop, 4th ed., (A.S.C. Holding, Hollywood), p.108.


Shooting Liquids

Liquids are usually not visible on film unless back lit. But even back lit liquids will not register on film very clearly. So special lighting must be used. We call these lights by their generic name, "Strobes."

These units are high intensity stroboscopic lights. Each time the aperture in your film camera is open, a strobe flash is struck. By shooting in slow motions ( high-speed camera ) one is clearly able to observe with much detail, images of moving objects that normally end up blurred. Using the strobes on liquids allows you to see sparkle on drops and makes liquid particles visible. The strobes get their sync from the camera's supplied sync connector.

Unilux is the leading manufacturer of these high intensity stroboscopic lighting equipment.

This is how they describe their product:

" The Unilux H3000 is a high-speed strobe lighting system that generates a high intensity light pulse used to freeze an object moving at a high rate of speed so it can be photographed with extraordinary sharpness. Unilux works with Arriflex BL's, SR3, 535 and 435; Panavision; Photosonics; Wilcam; Moviecam and Aaton cameras. "

" The Unilux H3000 is ideal for pour, spritz, spray and pop-type shots where the subject is moving. What's more, the award winning H3000 strobe system delivers maximum light intensity with minimal heat so sensitive subjects do not wilt, melt, blister or fade. (Unilux lights have a color temperature of 6500ºK.) "


We use these lighting instruments whenever we shoot liquids. You can also shoot people with the strobes but it's probably more desirable to simply shoot individuals with regular studio lighting diffused with Chimera Light Banks. According to the American Cinematographer Manual, "It is a common practice to utilize continuous sources (such as tungsten) with strobes. Typical practice is to light 2 stops under the strobe with the tungsten lighting up to one stop over. The more tungsten lighting, the softer the image."

Regardless of the on subject lighting choice (tungsten or other flicker-free source), "strobe-meisters" recommend the following:

1. Check your camera's film gate while the strobes are engaged to be certain that they are in sync. To do this, remove the lens off the camera, make sure the cavity is illuminated with the strobe and that the camera is running. The shutter should appear to be frozen in one position. "The control equipment for those strobes permits the addition of delay to the pulse in degree increments. The position of the shutter will either move forward or backward in relationship to the gate until it is in the proper position. For reflex cameras the strobe fires twice for each frame, once to illuminate the subject and a second time to illuminate the viewfinder."

2. Enjoy your shooting.

Visit my Places of Interest page to find a link to the Web Site of UNILUX and CHIMERA, respectively.

Some of the text was based on and quoted directly from the American Cinematographer Manual, 7th ed., (A.S.C. Press, Hollywood), pp.353-54.


Other Practical Information:

F / T Stop Numbering on a Zoom Lens
F-stops= White Numbers (16mm only)
T-stops= Red Numbers (16mm only)

Short prime lenses only have F-stops. Zoom lenses and long prime lenses have F-stops and T-stops. The "T" number takes into account the light lost due to the extra elements found in the particular lens. Consider a T-stop a very accurate F-stop. Use only F-stops for Depth of Field Charts.


Electricity: Amperage, Watts & Voltage Formula
Very often if you connect too many lights into one electrical circuit you will blow a fuse or trip the automatic circuit breaker. Use the formula down below to know in advance how many watts you can connect before you trip the automatic.

a = w
---
v
a
w
v 		= amps
= watts
= volts


Watts in the formula means the total number of watts connected to one circuit (electrical plug.) If you have three lights and each consumes 500 watts, your wattage number is 1,500. Volts in the formula means the local voltage amount running in the circuit. This can range from 110 in the U.S. to 240 in other countries.

If you know the local circuit handles only 20 amps, and your local voltage is 110, you know the maximum amount of wattage connectable is 2,200 watts. (20 x 110 = 2,200 / amps x volts = watts)

a = w
---
v
a
w
v 		= amps
= watts
= volts


When calculating power loads, also use the 70 percent rule. Many electricians advise not to load a circuit over 70 percent of its rated capacity. 2,200 x 0.7 = 1,540 watts. So, circuits theoretically capable of providing 2,200 watts, should be considered full at 1,540 watts.

Electricity: Other things to Remember
20 amps at 110 volts, for practical lighting purposes is the same as 10 amps at 220 volts. Remember this.

If you are shooting in a 220v country and your halogen tungsten lights run on 110, don't bring bulky 220v to 110v transformers. Simply install 220v bulbs in your lights. Only forgetful people bring transformers for 110v tungsten lights.

Voltages around the world are not all 110 volts. ASK LOCALS in advance what kind of voltage runs through their electrical outlets (mains) and then test to see if it's true.

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