mclarenblog.com

Lighting: Color Temperature theory and checking out lighting instruments.

When checking out lighting instruments please be aware of color temperature issues.

Color temperature theory – a short course.

If you were to take a piece of cold steel rod with no heat applied there would be no light energy emanating from it. If you were to place one end of that piece of steel into a furnace, the metal would first turn a brown red color. As more heat is applied the red tip of the steel would turn a bright red, even orange. Even more heat would then shift the color to a whiter looking yellow color. Finally as the tip heats up even further the tip of steel would appear to look entirely white.

The following list comes from Artist-Blacksmith’s Association of North America Inc. and lists the color of steel as it heats up. All the numbers following the color are Fahrenheit:

brown red: 1110F
blood red: 1200F
dark cherry:1290F
cherry: 1400F
light cherry:1490F
light red: 1600F
orange: 1710F
light orange:1800F
Yellow: 1920F
light yellow:2010F
white: 2190-about 2490F
incandescent:above 2490F

Above list obtained from http://www.abana.org/discus/messages/5/48.html
See also: http://www.abana.org/resources/education/tempil_guide.html

In a nut shell, what took place as the steel tip was being heated up was the atoms of steel electrons were first outputting long wavelengths of light. As more heat is applied the long wavelengths shorten to represent a higher energy level attained by the heated tip. As the wavelengths shorten the color temperature Kelvin number goes up.

Please understand that the voltage supplied to a lighting instrument is similar to a furnace. As the voltage goes up, the filament will send out shorter wave length light. The color shift, on tungsten instruments, will shift toward blue. Too high a voltage will obviously blow the bulb so this is for discussion only. If you decrease the voltage to a lighting instrument bulb the shift will go toward red. This can be done thought the use of dimmers. Please note that you can dim some lighting instruments like tungsten halogen but other lighting instruments can not be dimmed. When dimming tungsten halogen you can safely do so about 10% before the halogen cycle will fail to clear the bulb of tungsten residue build up. As you decrease the voltage to the tungsten bulb the light from that bulb will shift to red because of the diminished energy used to heat the instrument.

There are two principal color temperature lighting fixtures, 3200 and 5000 Kelvin.

From the theory section above, you should understand that 3200 represents lighting that comes close to lights one would find in the home, from incandescent fixtures. Conversely, the higher Kelvin number of 5000 represents the light coming from the sun.

Some typical color temperatures are:

1500 k Candlelight
2680 k 40 W incandescent lamp
3000 k 200 W incandescent lamp
3200 k Sunrise/sunset, and 3200K location and studio lighting.
3400 k Tungsten lamp
3400 k 1 hour from dusk/dawn
5000-4500 k Xenon lamp/light arc
5400 HMI
5500 k Sunny daylight around noon
5500-5600 k Electronic photo flash
6500-7500 k Overcast sky
9000-12000 k Blue sky

Above list obtained from: http://www.schorsch.com/kbase/glossary/cct.html but modified with additions by Donald McLaren.

Convention: do not mix lighting sources when shooting video or film. When shooting film match the lighting to the type of film. This is a basic mistake made by beginning students. It is quite easy for an instructor to spot this type of mistake as parts of the picture might be seen as blue while other parts of the scene will be red in color cast. The reason one would see two color casts is that the ambient light is typically one color but the lights that the student brings to the shoot do not match in color temperature.

Exception: The TV show NYPD Blue uses a blend of color temperatures. They color balance the cameras to be between daylight and tungsten. When they shoot, you will see the slight blue cast of daylight and the slight cast of red of practicles. The shift is slight because the camera is in-between the two extremes. Also, they allow light to come into the scene that they can not control and blow out the exposure. These are professionals and know when and how to break with convention.

Example: If you are shooting with daylight film then check out lights that are around 5000 Kelvin.

Daylight Film (expects “blue” white light)

HMI lights are blue, typically matched for daylight, so use them straight – no filter.

Florescent lights (Kino Flow) with 5000 Kelvin tubes.

Tungsten Halogen 3200K with blue filter, CTB. Most of these instruments are 3200K and need a blue filter.

Tungsten Halogen with 5600K bulb – no filter. (We do not have this type of bulb, so use a filter instead. Just understand that this is a rental house option.)

When shooting indoors and daylight is coming through the window no filter is necessary except maybe a ND.

When shooting indoors and existing practicals are being used, gel or relamp the instruments with 5000k unless you want the red, ruddy look of the practicals.

Example: If you are shooting with indoor film then check out lights that are 3200 Kelvin.

Indoor Film (expects “red” white light)

Tungsten Halogen 3200K – no filters needed.

Florescent lights (Kino Flow) with 3200 Kelvin tubes.

HMI puts out daylight so an orange filter is required, CTO.

When shooting indoors and outside sun light comes through a window, gel outside windows with orange filter with or without ND. Installing gels on windows can run into money.

When shooting indoors and existing practicals are being used, that’s just fine. The practicle color temperature is close enough.

Vocabulary term: PRACTICLES 1. A light that will or might appear in a shot such as a table lamp, floor lamp, street lamp, etc. 2. A lamp that would normally be seen in a shot for that type of location. 3. A light that can be placed into a shot, with the intention of being seen, thus allowing the lighting people to place another light, not seen, typically above, that supplies a more precisely controlled amount and directed light. 4. A light that allows motivated light, other lights to be used out of sight. 5. Director of Photography, Lighting Designers, Lighting Directors typically plead with the set designers to include practicles throughout the set so they can achieve motivated light sources from these practicles.

Question: Why can’t I see the color change of different light sources with my eyes but my video camera shows those differences up as drastic color changes.
Answer: Our eye, brain, system has an automatic color temperature system that will minimize the effect while video and film cameras are locked in their rendition of what is viewed. The video camera typically does have a white balance function that allows the camera to shift to the correct temperature.

Following are some examples of gel filters used to correct “wrong” color lighting instruments.

Full CTB gel is used on our 3200 tungsten instruments.
Light loss: 1.7 stops typical
Transmission: 24% typical.

Converts	To
3200K	5500K
5600K	34,480K
2210K	3200K
3130	5600K

Vocabulary Term: CTB, Color temperature blue.This is a blue gel that converts 3200K lighting instuments to function in circumstances where daylight color temperature is required.

FULL CTO gel can be used on HMI lights to allow those instruments to be used with 3200K.
Light loss: .5 stops typical
Transmission: 62%

Converts	To
3200K	2180K
5600K	3090K
6010K	3200K
30,689K	5600K

Vocabulary Term: CTO, Color Temp OrangeColor temperature orange refers to a filter that is used to shift the white blue cast light comming from 5000K instuments and shifts that light down to a warmer temperature of 3200K.

Ideally: It should be noted that to use a lighting instrument that is directly inappropriate and requires a gel to bring the light into the correct temperature is wasteful. Any gel has a ND factor, a neutral density, that cuts down on the amount of light that reaches the scene.

Reality: Do what it takes to get the lighting job done. If that requires putting up a gel then do it. Just remember that you might have to put up two lights of the wrong type against one light of the correct color temperature type to get the job done due to the ND factor.

Vocabulary Term: ND or Neutral DensityND or Neutral Density is the amount of light that is decreased by going through a filter. Typically this refers to a neutral color such as a shade of gray that will not shift the original light to a new different color. Now saying that, every color filter besides shifting the output color to some new shade must also have a ND factor included. Just think in your mind of a slightly rosy filter. By being slightly red in color it will pass most of the light. Now think of a dark red filter. By making the resulting light dark red it also cuts down the light a lot. It is said to have a higher ND factor. When selecting filters, just beware that when you slide a color filter into a lighting instrument, the amount of light falling on the set from that light will decrease.Realize that there are ND filters that you can use to cut down the amount of light reaching the set but do not change the color. You can recognize these filters by their color – shade of grey to black.

Here is an example of one manufacturer, GamColor, neutral density filters.

Gam Color Filter number	ND Factor	Light loss in F stops
1514	.15 ND	.5 Stops
1515	.3 ND	.9 Stops
1516	.6 ND	1.7 Stops
1517	.9 ND	2.5 Stops
1518	1.2 ND	2.7 Stops

Dichroic Filters

Dichroic filters may be the best solution for filtering “wrong” lighting instruments for the following reasons:

• Dichroic filters reflect unwanted wavelengths back to the light source. Gel filters absorb the unwanted wavelengths and dissipate them in the form of heat, ultimately leading to performance degradation (melting, bleaching out, scorching, etc.).
• Dichroic filter transmission levels are substantially higher than an equivalent gel filter providing considerable savings in energy and money.
• Dichroic filters are highly color selective producing brighter, cleaner appearing, saturated color.
• Dichroic filters will not melt, wrinkle, shrink or fade like gel filters.
• Dichroic filters retain their characteristic spectral transmission properties indefinitely for long life and value.
• Dichroic filters are low maintenance and seldom if ever require replacement.
• Dichroic filters offer superior performance and long term cost savings.

The above list was obtained from http://www.highend.com/news/dichroic.html.

The down side of dichroic filters are listed next:

• They break easily.
• They are expensive compared to gels.
• Gel filters can be attached to just about any lighting instrument. Dicroic filters usually have to be made for a particular instrument.
• Some college campus equipment check out rooms not have any of these filters because, in the hands of students, they would not last very long.

Troubleshooting the obvious and less obvious:

• Camera will not run.
  • Check to make sure the motor clamp is snug. The camera motor body is the return electrical path and must be touching the motor housing clamp tight enough for a good electrical contact.
  • The film buckle switch might not have been set properly. Open the sprocket wheel mechanism and then close. You don’t see it but a little plunger resets the film buckle switch to the “ON” position by open and closing the thread mechanism.
• You can not see an image.
  • Obviously, there is a lens cap and I would hope that that cap is not on the front of the lens.
  • The viewfinder might have a cap over it. Swing the cap out of the way. We have one camera that has a automatic iris that closes out the light from the viewfinder unless the operator places his or her eye up to the viewfinder and presses against the eye cup. The pressure opens the iris and allows the operator to view and image.
  • Each lens has a iris adjustment. Rotate the iris ring to full open.
  • The viewing mechanism employs a front surfaced mirror to direct the lens image to the viewfinder while the film is being pulled down inside the camera. It is a 50/50 percent chance that when the camera is stopped that the shutter is open allowing the lens light to the film but denying you the ability to see anything from the camera viewfinder. The solution is simple. Just rotate the camera motor shaft a bit, that is the little knob at the rear of the motor.
  • Are you using a telephoto lens or zoom in full zoom in setting? It is quite possible to be so closely zoomed into a blank wall or other surface that nothing will appear in the viewfinder. Pan or choose a wide angle lens.
  • The camera has three lens mounts. Make sure that you do not have the lens turret set between lenses.
• Image is out of focus.
  • Did you set the diopter first? Setting the diopter is the first step you should complete before thinking about using any lens. Just take the camera with or without a taking lens and shoot something blank like a white wall, the north sky if outside, or the sidewalk. Concentrate on a ground glass image in the viewfinder. Make darn sure that that ground glass is as sharp as you can make it for your eye by rotating the diopter ring close to the eye cup. Whenever any camera person uses the camera, that person and only that person must reset the diopter. Never set the diopter for another camera person!
  • Now that the diopter is properly set, do not change it but lock it in place using the lock ring.
  • Take the lens you intend to use and set it to infinity focus. The infinity marking on a lens is a figure “8″ laid on its side. Infinity is a fantastic way to calibrate a lens or check its calibration.
  • Take the iris ring and open it ALL the way. Do not stop it down one little bit. It must we wide open to remove any depth of field. [Dept of field is the area between a near and far point from the lens that shows acceptable focus.]
  • Through the viewfinder, look at an object with fine thin lines at infinity. Now lets get real here. Just pick an object at least a quarter a mile away. Power poles, power lines, high rise buildings with windows, edge of a tall building, tall trees, etc. Now we are going to concentrate on the fine lines of one or more far distant objects. Rotate the lens focus ring and rock the ring back and forth until you get the best focus.
  • Is the image sharp? Take into consideration that the image is composed on to a ground glass and the image by definition can not achieve any fantastic detail with this method but it should look sharp.
  • Look at the setting of the lens focus ring. Is it right on the infinity mark? If it is not, either you did the diopter adjustment wrong or the lens is out of calibration.
• Image seems out of focus (more rigorous check).
  • Obtain a Siemens star target and place it at a convenient distance from the lens. This will require that you also have a tape measure. Look at the lens and look at the lens markings for distance. Choose a distance from the camera corresponding to a mark found on the lens. In this way we can get more precise as to any error. Most cameras have a film plane marking to indicate distance measurements. On the Arri S is on the opposite side of the operator close to the matt box attachment. The mark looks like a circle with a line running through it. One of the tape measure should be placed at that mark. Place the target Siemens star at a precise distance from the camera.
  • Perform the viewfinder ground glass focus as described above. Make darn sure this is as precise as you can get.
  • Now open the lens all the way. We want minimal depth of field.
  • Rotate the focus lens ring back and forth to make the Siemens star appear as sharp focus as you can get. Please remember that ground glass focus method is not going to be immaculate because the ground glass will soften any image. Just concentrate on the lines you see in the lens and stop when the target gets sharp.
  • Now with the lens left where you found the best focus, compare the lens reading to the measured distance of the Siemens star to camera distance. The two distances should be within four inches of each other. It they are not then a problem exists with the camera or the lens. Do not use the camera but return it to checkout and tell them that the tape vs eye measurements do not coincide.

  NOTE: Lens back focus is different with each model camera. Lens back focus is the distance behind the lens where the real sharp focus occurs. This sharp focus must occur on the film emulsion as it sits in the film camera aperture. Occasionally we send in our zoom lenses for collimating. Some zoom lenses are matched for a particular camera. In addition, an exact lens opening on the turret is optimum and sometime comes with a special marking. For most student projects you should not care which zoom lens goes with which camera. In the professional field you will take great care that the lens properly matches the correct camera. In any case, do not use lenses intended for another camera as the back focus might and probably will be wrong.

The information here is for educational and reference use only. Decide on your own how to proceed in performing any repair you face. We do not accept any responsibility for this information being entirely accurate. We hope it is accurate. Most of the information posed here has been noted to be significant, used in the repair process, and to some extent tested for accuracy through the actual discovery and recording of performing a repair. If you decide to use any of the information here, try to keep in mind that a number of factors may change when you attempt the “same” repair. Models do change from apparently being same units. Their are definitely different methods of making a repair. The steps that you should use to achieve a successful and expedient repair might be different. The problem you face with a piece of equipment might be similar but not an exact match to what we faced. Just use common sense and always be a bit skeptical of following our methodology until you feel that you and we share the same viewpoint and tactics.

Good flavor. Excellent price. Enjoyable in all respects.

I am the canary in the coal mine. If there is any chemical additive in meat, I will get a headache. This is also some times true with wine. I can not figure out why I get headaches with wine. I do not think additives are the cause, but I am not sure of that. This wine created no headache the next morning.

My doctor told me to drink wine as it might help my symptoms from my blood thickening. In order to get the same benefits from drinking wine, I try to take Longevinex but the cost is close to $1 a pill. I love to sip wine and write this blog. I do not get headaches from Longevinex but some times it is just more fun to sip the wine instead of popping a pill.

Simply awful tasting wine. It tasted like it was altered. I picked up the taste of clove. We threw the contents of the bottle out. This is most surprising as Yellow Tail has been an ok wine for us in the past.   Yellow Tail is made in Australia.

My wife and I took a honeymoon cruse on a cruise line that offered French wine with just about every dinner. Before, during and after that cruise just about every French wine we had was disappointing due to the impression that the wines were watered down. That cruise really created the impression we now have about European wines. At other times drinking Italian wines, for me, have had the same impression, anemic flavor. I have suspected that some French vintners, have allegedly stretched their purse strings by being allowed to bottle more through the addition of water to their wine vats. It seems inconceivable to me that in one continent the wines could be so lacking in flavor. Could it be that the more expensive wines are just not watered down? In my opinion, it seems that just about every other continent can offer robust flavors except Europe. We think South Africa, South America, Australia, and New Zeland can pretty much stand up, and even surpass, California wines. We use California wines as a bench mark to judge any other wines because we live in California.

I do hope that no United States winery would modify their wines with any watering down process, chemicals or additives. My wife thinks that air might have reached the wine leading to the altered taste. I am not so sure.

Bureau of State Audits presented its audit report concerning the California State University’s (university) compensation practices.

“Average executive compensation increased by 25.1 percent over this time period, with salary increases contributing the most to the growth. Average compensation for Management Personnel Plan employees (management personnel), such as managers and professional technical staff, increased by 10.4 percent. In contrast, average compensation for tenure-track faculty and other faculty increased by 5.6 percent, and 6.2 percent, respectively.”

“The chancellor’s office establishes systemwide compensation policies but does not have a system in place that allows it to adequately monitor adherence to those policies and to measure their impact on university finances. Specifically, the chancellor’s office does not maintain systemwide compensation data by type and funding source, either by individual or in total. The lack of this data impairs the ability of the chancellor’s office to provide effective oversight of the university’s compensation programs.” (page 18).  “Some management personnel received questionable compensation after they were no longer providing services to the university or while they were transitioning to faculty positions. ” (cover letter).