Difference between revisions of "DIY Flourescent Area Light"

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Note that you can buy those kinoflo tubes "spare part" also, in the same price range (http://www.filmandvideolighting.com/2ft55tub6pac.html) - though we do not know if the Kinoflo ballast treats the tubes in a special way that enables/improves their performance.
Note that you can buy those kinoflo tubes "spare part" also, in the same price range (http://www.filmandvideolighting.com/2ft55tub6pac.html) - though we do not know if the Kinoflo ballast treats the tubes in a special way that enables/improves their performance.
One must understand that a PLL bulb (like dulux series) is in practice inferior to T5 and T8 bulbs of the same CRI rating. That is because fluorescent lights are very sensitive to heat. Heat dissipation is therefor key and must certainly be taken into consideration when positioning the lamps. A dulux-type bulb for instance will change in color when positioned upright and that effect will increase as when the foot of the lamp is at the bottom size when vertically mounted. That effect is less noticable with T5 and T8 technology. In fact, T8 is the most superior lamp because in comparison to T8, heat dissipation is taken into account.
A common misconception is that CRI is the only way to rate a lamp in terms of color quality when using a photo technique such as film or video. One must know that two high-CRI lamps can still be very different in color tests. One must understand that a non-linear spectrum can cause content-sensitive subjects such as human skin to be portrayed unnatural or unpleasing.
Technologies such as HMI and T8 and T5 fluorescent are still superior to phosphor-corrected high-CRI LED's and PLL because the spectrum suffers less 'spikes' in human-sensitive areas as skintones.
Also one must note that a particular light mostly doesn't come alone on a filmset for instance. Many times multiple units must light along eachother. The problem of batching (which comes with LED's) means that it is very likely to find the same units of the same rating from the same manufacturer will have a different spectrum.
Color quality, white balance and CRI diminishes with almost all discharge-types of lamps such as HMI and fluorescent. While this process is slow, in practical terms this is of lesser concern since lamps can be filter-corrected.
One must note that color filtering by means of color gel does not solve the problem of 'bad' CRI. A part of the spectrum can be arbitrary balanced, so a particular color on set will look ok, but that gel will not work for other colors.


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Revision as of 22:12, 6 January 2014

1 Disclaimer

This page is the result of the discussion that started on the apertus forums: http://www.apertus.org/forums/viewtopic.php?f=4&t=662

Currently it is a collection of information required to actually build one of these.

As always with DIY products that use electricity: be careful - don't kill yourself or your cast and crew - hands off if you don't know what you are doing!

Divalite400.jpg

2 Facts

2.1 General

  • Normal fluorescent lights as they are used in buildings, parking lots, offices, etc. are unsuited as they flicker with twice the grid frequency (100/120 Hz) and this gives a pumping or flicker effect when shooting video. So what we need are high speed electronic flickering fluorescent tubes (35-45 KHz). At this frequency the flickering overlaps and this leads to a constant light flux with no noticeable fluctuations in light intensity.
  • We need a fluorescent tube, an electronic controller (called ballast) and a starter (sometime integrated in the ballast).
  • The ballast provides a high initial voltage to initiate the discharge, then rapidly limits the lamp current to safely sustain the discharge.
  • There are 2 types of ballasts: Electromagnetic ballasts (strong flickering and humming audible noise) and electronic ballasts (high frequency = unnoticeable flickering, no audible noise) <- so this is the one we need: Wikipedia: Fluorescent lamps using high-frequency electronic ballasts do not produce visible light flicker, since above about 5 kHz, the excited electron state half-life is longer than a half cycle, and light production becomes continuous.
  • Fluorescent ballasts are manufactured for three primary types of fluorescent lamps: preheat, rapid start, and instant start.
  • Only "rapid start mode" ballasts are suitable for dimming
  • Dimming might change the color temperature of the light (depending on tube quality)

2.2 Tubes

Tubes that some DIY cinematographers are already using:

Osram-dulux-l-he.jpg

  • Osram Dulux L 55w 930 (Tungsten)
  • Osram Dulux L 55w 954 (Daylight)

or 100% compatible:

  • Philips Master PL-L 930 4P (Tungsten)
  • Philips Master PL-L 950 4P (Daylight)

These cost around 6 - 20€ each and are easy to source locally.

They all use a 2G11 socket.

Dulux L lamps are specially designed for television studio lighting. They provide high lumen packages and offer excellent color stability, even when dimmed down to 50%. The special phosphor allow them to seamlessly blend in with the light from other tungsten (warm) or metal halide (daylight) lamps on the set.

2.2.1 Color Rendition Index (CRI)

The first number (in 930 & 954) is the color rendition level.

9 = 90%+ color rendition fidelity (see http://en.wikipedia.org/wiki/Fluorescent_lamp#Color_rendering_index).

Kino were the first to manufacture tubes with this 95+% color rendition fidelity which might be even better than the one by Osram outlined here.

Note that you can buy those kinoflo tubes "spare part" also, in the same price range (http://www.filmandvideolighting.com/2ft55tub6pac.html) - though we do not know if the Kinoflo ballast treats the tubes in a special way that enables/improves their performance.

One must understand that a PLL bulb (like dulux series) is in practice inferior to T5 and T8 bulbs of the same CRI rating. That is because fluorescent lights are very sensitive to heat. Heat dissipation is therefor key and must certainly be taken into consideration when positioning the lamps. A dulux-type bulb for instance will change in color when positioned upright and that effect will increase as when the foot of the lamp is at the bottom size when vertically mounted. That effect is less noticable with T5 and T8 technology. In fact, T8 is the most superior lamp because in comparison to T8, heat dissipation is taken into account.

A common misconception is that CRI is the only way to rate a lamp in terms of color quality when using a photo technique such as film or video. One must know that two high-CRI lamps can still be very different in color tests. One must understand that a non-linear spectrum can cause content-sensitive subjects such as human skin to be portrayed unnatural or unpleasing. Technologies such as HMI and T8 and T5 fluorescent are still superior to phosphor-corrected high-CRI LED's and PLL because the spectrum suffers less 'spikes' in human-sensitive areas as skintones.

Also one must note that a particular light mostly doesn't come alone on a filmset for instance. Many times multiple units must light along eachother. The problem of batching (which comes with LED's) means that it is very likely to find the same units of the same rating from the same manufacturer will have a different spectrum.

Color quality, white balance and CRI diminishes with almost all discharge-types of lamps such as HMI and fluorescent. While this process is slow, in practical terms this is of lesser concern since lamps can be filter-corrected.

One must note that color filtering by means of color gel does not solve the problem of 'bad' CRI. A part of the spectrum can be arbitrary balanced, so a particular color on set will look ok, but that gel will not work for other colors.

2.2.2 Holder

https://www.google.com/search?tbm=shop&q=2G11#hl=en&tbm=shop&sclient=psy-ab&q=2G11+holder&oq=2G11+holder&gs_l=serp.3...5276.6284.0.6432.7.7.0.0.0.0.248.1003.0j5j1.6.0...0.0...1c.6ZELMcl-8IQ&pbx=1&fp=1&biw=1366&bih=571&bav=on.2,or.r_cp.r_qf.&cad=b&sei=dY1mUZbcIev74QTurIG4Aw

2.2.3 Tube designations

When you research fluorescent tubes you will immediately stumble over designations like T8, T5 or T12.

Quite simply, "T" is the diameter of the tube. A T12 bulb will have a diameter of 12/8" (3.81cm).

Please note that the recommended tubes above are twin tube designs and do not follow the T standard.

Typically the more narrow the lamp, the more efficient and the more expensive it will be. Different designations also use different socket types (from http://en.wikipedia.org/wiki/Fluorescent-lamp_formats):

Fluorescent tube diameter designation comparison
Designation Tube diameter Extra
(in) (mm) Socket Notes
T2 1/4" approx. 7 WP4.5x8.5d Osram Fluorescent Miniature (FM) tubes only Havells Sylvania Luxline Slim T2 Linear
T4 1/2" 12,7 G5 bipin Slim lamps. Power ratings and lengths not standardized (and not the same) between different manufacturers
T5 T16 5/8" 15,9 G5 bipin Original 4–13 W range from 1950s or earlier.
T8 T26 1 25,4 G13 bipin/single pin/recessed double contact Currently not available in 3200K (tungsten) color. Will require correcting filters such as CTO 1/4 or 1/2 on a 4200K bulb.
T9 T29 1 1/8" G10q quadpin contact Circular fluorescent tubes only
T10 1 1/4" G13 bipin
T12 T38 1 1/2" G13 bipin/single pin/recessed double contact not as efficient as new lamps

2.3 Ballast

  • Dimmable ballasts are in general more expensive (50-90€) than non dimmable ones (20-30€)
  • The ballast needs to match the watts of the used fluorescent tube
  • Some ballasts can supply 2 fluorescent tubes (indicated with markings like "2x58W")
  • The Osram ballasts matching the Dulux L series are called T8 high frequency electronic ballast: QUICKTRONIC
  • The Oscram Quicktronic dimmable ballasts have a digital interface (called DALI) that lets you control the lamps electronically: http://en.wikipedia.org/wiki/Digital_Addressable_Lighting_Interface <- Arduino based wireless light control over bluetooth anyone?
  • There are many 1-10V electronic dimmable ballasts in many power ratings available from such manufacturers as Phillips and Osram. Unlike the analog 0-10V dimmers, these units provide voltage, so one can easily dim them by putting a potentiometer in series. The way to dim them with an Arduino, is by means of a mosfet.

3 Energy Efficiency

Everyone talks about LEDs recently and how they are going to replace traditional light bulbs.

But lets take a look at the facts:

3.1 The Theory

Wikipedia: http://en.wikipedia.org/wiki/Luminous_efficacy

The luminous coefficient is luminous efficiency expressed as a value between zero and one, with one corresponding to an efficacy of 683 lm/W.

So the maximum physically possible output of one Watt of electric power are 683 Lumens of light. Depending on this efficiency the rest of energy is converted to heat rather than photons/light.

Lamp Type Luminous Coefficient
Candle 0.04%
Tungsten Incandescent Bulb 2 - 3%
Tungsten Halogen 2.5 - 3.5%
LED 0.7 - 15%
Fluorescent Tube 9 - 15%
HMI 9.5 – 17%

So Fluorescent Tubes are just as energy efficient as LEDs and have been around for quite some time already.

4 Various Instruction Videos (not necessarily related to the above information)

http://www.youtube.com/watch?v=O7LNXLu9Z6g

http://www.youtube.com/watch?v=uIxy6p4kzd0

5 Kinoflo Diva 401 Tear Down

We were very curious what was hiding inside the Diva light enclosure, what electronics we would discover there and what other parts they used.

tubes in socket
front
back side with assembled enclosure
back side with removed enclosure: ballast Osram Quicktronic Deluxe HF 2x58W Dim
ballast Osram Quicktronic Deluxe HF 2x58W Dim
left side connectors and parts
right side connectors and parts