lighting research


Many LED luminaires do not use high frequency drivers to eliminate flicker in the same way high frequency fluorescent lamp ballasts eliminate flicker. Shooting video in environments with  a lot of LED luminaires can produce video with distracting flicker. Viewers do not want to be distracted, and will switch off  if they see annoying flickering.

LED Lighting Video Recording Tips?

To eliminate flicker, for 120V 60Hz locations, the best shutter speeds to use are at multiples of 120, while at 220/230V 50Hz power locations, best shutter speeds are in multiples of 100. This Telegraph video seems to have been shot at 25 fps, which may be why a lot of annoying flicker can be seen. For flicker free video in 50Hz electrical environments, shooting at 50 or 100 fps should give best flicker free results, for 60Hz, 60 to 120 fps should give best results

For 50Hz 1/100, 1/50, 1/33, 1/25. 50 & 100 fps should = best results
For 60Hz 1/120, 1/60, 1/40, 1/30. 60 & 120 fps should = best results

This video should most likely have been recorded at 100 fps or 50 fps. In post-production there is no fix for this strobing effect. The only solution is to test other camera settings & re-shoot.

A best approach when Designing Architectural Lighting is to specify LED luminaires with high frequency, flicker free dimming drivers.

See full video & Telegraph article here: http://bit.ly/1cvuZxH

 There seems a mad rush to use blue light in your Fridge.

FrigdeSmallPic

A new stainless steel fridge might look nice in your kitchen, but open the door.

What do you see? Is this what food looks like on your kitchen counter or table?

Is this what the food looked like when you bought it?

Light, and the colour of light, affects how we see the environment around us.

Do you want to see food that looks artificially cold, or do you want to see food in the correct light?

The purpose of fridge lighting is to communicate information; we need to see food, and its colour, to decide if it is healthy to eat.

Does a steak look blue, grey, or red fresh and ready to cook & eat? The colour of food helps tell us if is healthy to eat. Is opening your fridge a pleasurable experience?

Can you see everything? Does the food look good? What can you see?

LEDs can provide excellent optical control of light beams in low profile housings. Fridge interior area lighting may be improved with multiple low profile LED lights vs. past methods that used a single fridge lamp.

LED lighting does not have to have poor colour rendition. It is possible to have correct and accurate colour LED lighting in fridges.

Does the food in your supermarket refrigerator case look correct? Much supermarket food is now being lit with linear strip LED lighting. Custom LED lamp phosphor blends can offer accurate colour lighting.

What do you see inside these fridges? Does this look like food you want to eat?

Could fridge interior blue light imply a false sense of food temperature & appearance?

Will blue colour light make you think food is cold, when the fridge is off?

Does fridge lighting make food look like un-ripened fruit that should be left to ripen, but due to colour appearance might be left to rot?

Accurate light colour rendition seems a common sense consumer protection safety issue.

Should a 2000 dollar fridge come with a 2 dollar light?

Fridge interior visual design experience is important, as is accurate and well placed glare free lighting. Fridge manufacturers need to invest in more in how and what consumers see, to meet expectations, and ensure food safety.

There are standards for lighting colour quality.

Do consumers need protection from poor quality lighting colour? Yes they do.

A global view of the food we eat  look & listen to NPR’s review of the book,  ‘Hungry Planet: What The World Eats’   Photographer Peter Menzel and writer Faith D’Aluisio visited 30 different families around the world noting the food they eat

Light & Colour – Conversations:
For insights on conventional light sources vs. LED sources and their colour rendering performance for Film & DSLR video see these tests.

I. The Academy of Motion Picture Arts & Sciences, Science & Technology Council Solid State Lighting Project

“The Academy of Motion Picture Arts & Sciences, Science and Technology Council has identified a need for an unbiased investigation of solid state lighting (SSL) technologies, which includes LED emitters, for motion picture production. Issues with SSL have been identified regarding its ability to supplement and integrate with existing lighting technologies such as tungsten, fluorescent, HMI, and Xenon that are currently used in the production of motion pictures. The primary purpose of this investigation is to provide the industry with data needed to properly evaluate the impact of using SSL, as well as to provide a framework for the evaluation of future light emitting technologies as they are developed. The Council’s current efforts are focused on providing the motion picture industry with accurate and previously unpublished radiometric and photometric measurements (e.g., spectral power distribution, radiant flux, luminous flux, etc.) typical of various LED light sources currently in use.”

Seven Symposium Videos:

  1. Jonathan Erland Speaks on the Science of Color
  2. Perception of Color
  3. Reproduction of Color
  4. Council Studies
  5. Measurements
  6. Emulsion and Color
  7. Summary

Six Lighting Test Shoots:

  1. Makeup Case
  2. Costume Case: Part 1
  3. Costume Case: Part 2
  4. Props Case: Part 1
  5. Props Case: Part 2
  6. Props Case: Part 3

IIa. Zacuto 2010 Shoot Out – Film Vs DSLR 2010 (episodes 1,2,3)

Zacuto Films presents, “The Great Camera Shootout 2010: a three part web series where gunslinging HD DSLRs face-off against legendary 35mm Film.” The webisodic series showcases the top performing hybrid HD-DSLR cameras: Canon: 5D MKII, 7D, 1D, 550D/T2i Rebel, Nikon D3s, Panasonic GH1 and compares the image quality of these cameras against the gold standard of 35mm film. In addition, the Canon 5D MKII test includes the new 24p firmware. “This was an enormous undertaking,” says Steve Weiss, Web Series Director, “and great care was to make this an apples-to-apples test with scientific accuracy behind it.”

Each webisode of the series features various controlled camera assessment tests which include: resolution, latitude, sensitivity, speed & ultra high speed, noise, color & green screen. The battery of tests were administered under strict controls and conducted by Robert Primes ASC, Gary Adcock, Philip Bloom, Jens Bogehegn and colorist Ryan Emerson.

See the reactions to this test following 2K screenings, where “HD DSLR is compared to 35mm Film”. The test results were projected in a 2K theatrical environment at three screening locations: Stag Theater at Skywalker Ranch, LucasFilms Ltd., AFI (American Film Institute) Theater in Hollywood and the FilmWorkers Astro Color Timing Theater in Chicago. Hear commentary from the screenings by top ASC, Hollywood, Indie Film and Event & Convergence Photographers.

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IIb. Zacuto 2011 Shoot Out – Film Cameras Vs High end Digital Film Cameras (episodes 1,2,3)

The 2011 shoot out includes new cameras & tests of Single Chip Camera Evaluation (SCCE) which is a large scale technical camera comparison administered by Robert Primes, ASC. Side by side comparisons of the newest cameras manufactured by Sony, Canon, Panasonic, Phantom, Weisscam, Nikon, Arri, RED as well as the gold standard of 35mm film are included.

Film Stock: 2-Perf & 3-Perf 35mm Motion Picture Film Demo

More on Colour Editing & Management in Post Production
From Shane Hurlbut:  7 Tips for HD Color Correction and DSLR Color Correction

A Short History of Compositing for Film & Video

Oscar Winner Petro Vlahos Inventor of the Ultimatte discusses his invention and how he used UV and Low Pressure Sodium lighting methods, which evolved into to the Blue & Green Screen chroma key compositing methods we use today.



A video demo from NAB 09

Babies undergoing phototherapy for hyperbilirubinemia, have eye masks to prevent risk of UV exposure and to eliminate risk of retinopathy of prematurity. Lights in neonatal wards are not allowed on 24 hours a day. Direct & bare lamp use is not allowed.

Phototherapy lamps used have a special phosphor coatings only for bililights. As an added precaution the bililights I designed use a museum quality acrylic UV filter.

Newer medical research indicates a slight shift in action spectrum may speed photo therapy. LEDs can be used for this phototherapy. Much research has found them to be as effective as the special fluorescent bililamps, however as LEDs have a more pronounced spectral peak, it may be possible that superior combination of LEDs and phosphors may replicate a faster reacting action spectrum.

LEDs can offer similar, if not the same phototherapy as the best fluorescent bililamps, but as all lights dim in brightness as they age, control algorithms for LEDs can ensure maintained light levels are delivered for a 15 year bililight source service lives. This is not yet being done for phototherapy but I trust testing may soon start.

Both terms and their effects, need simultaneous review when discussing LED performance decline over time.

Depreciation commonly is used to refer to the decline in brightness over time as a light source is used, known as lamp lumen depreciation.

LEDs also degrade.

Degradation, many may think of chemical decomposition but there is also elegant degradation. One or both of these conditions seems commonly referred to, and one or both, may occur at the same time.

LED performance depreciates over time as less lumens are emitted. The more any light is used, the more a light source brightness dims over time.

LED lumen depreciation can be solely due to heat conditions. Research has verified this independent of LED operation.

Evidence of LED lamp lumen depreciation is useful, however we know in addition to lumen deprecation, LED Kelvin CCT (Correlated Color Temperature) changes over time.  If change in apparent colour appearance of an LED, and lumen depreciation are plotted at the same point, we can see how these changes may parallel each other in some LED sources, while for others, they may be independent.

Decline in LED lamp lumens and colour temperature change over time varies between manufacturers. It seems sensible to test LED Kelvin CCT measurements and plot them at the same time as Lumen measurements are taken when LED life performance testing is conducted.

LED lumen maintenance curves decline due to LED use and thermal conditions.

All lamp lumen performance declines due to use. Lumen maintenance curve decline is also affected by the number of times a lamp is turned on & off, the thermal environment of the lamp and luminaire, and lamp ballast/driver electronics.

New research shows LED lumen performance declines due to heat without LEDs being turned on. During testing LEDs were turned on only for short duration lumen measurement data collection.

This has large implications for exterior LED lighting where high ambient temperatures are present, as is typically found inside luminaires exposed to direct sunlight during daytimes when luminaires are not on.

The higher the ambient temperature, the faster LED lumen performance declines. Not all high brightness LEDs perform the same way.  Different manufacturer’s LEDs exhibit different rates of decline.  Variation in lumen performance decline must be due to differences in LED manufacture technique and material.

I am interested to review Electron microscopic time-elapse images & data collected at different points along the lumen maintenance curve. No doubt, there is something new to discover to improve manufacturing technique & fabrication for more robust LEDs.