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LED lights for diffuse macro lighting

Discussion in 'Accessories' started by addieleman, Feb 20, 2013.

  1. addieleman

    addieleman Mu-43 All-Pro

    Aug 5, 2010
    The Netherlands
    Ad
    I'm thinking of buying some LED lights for macro shots. I want to have fairly diffuse lighting so I'm looking into the ones with a number of LEDs in a square.

    Anyone using these? How much light do you get from them? How is colour rendition, any weird colour casts? Anything else to watch out for? Thanks!
     
  2. b_rubenstein

    b_rubenstein Mu-43 All-Pro

    Mar 20, 2012
    Melbourne, FL
    I bought a small $40, 120 LED panel that came with a color correction panel. I also bought a the Fotodiox Pro LED 312AS panel. The panels aren't very large, so they have to be placed fairly close to the subject for diffuse light. At 20 - 50 cm they put out a very useful amount of light. The one real issue with these inexpensive panels is color balance. Not only are they off, but the spectrum seems to be discontinuous and hard to correct even with a custom WB. I still think they are worth getting to experiment with.
     
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  3. MajorMagee

    MajorMagee Mu-43 All-Pro

    Feb 24, 2011
    Dayton, OH
    The problem with color balance is because the undelying chip that emmits the light is very narrowly emmiting blue light, and then they pass that through yellow phosphors to make it look white. It really is not a very easy light source to white balance for.

    LEDWhiteSpectum.
     
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  4. 0dBm

    0dBm Mu-43 Top Veteran

    859
    Jun 30, 2011
    Western United States
    I use the Cineroid product that contains a bank of 8x12 high-power LEDS. Each LED contains three dies so the light product output is even greater than 288 5mm single-die LEDS.

    My unit is the 5000 Kelvin color temperature unit. I chose it over the warmer-tinted 3000 Kelvin unit because I can use a CTO gel to adjust the color temperature down.

    Be careful with the budget-priced, single-die LEDs arranged in a bank that are proliferating in the marketplace. Most of these use the 5mm (physical size) Nichia (or clone) (1000-4000 millicandela output) LED. These LEDs typically have a higher color temperature that range from 6000-8000+K which tend to gravitate to the blue end of the color spectrum.

    An additional problem with these budget-priced "bank" lights is that they use "bargain-bin" LEDs with varying color temperatures so that the overall output is NOT consistent. The so-called "color-cast" may be severe in some of these products. I have seen significant color variations. If the deteriorated eyes of a human in his mid-late 50s can see such phenomenon, measuring instruments will indicate severe variations.

    The higher cost of the better-quality LED lights, whether for video, photo, or other applications is due the use of high-power (ne' high-output) LEDs; careful selection of the LEDs to minimize variation in tint; the construction of the housing; and the quality of the regulation of the current output of the power supply used. LEDs are current-controlled devices and their light product outputs will vary depending on the level of current supplied to them. The more consistent the current, the more consistent the output (ceteris paribus). As supplied current drops, color temperature drops accordingly (but not necessarily proportionately).

    Without the use of a parabolic reflector that is designed to collimate ("collect" and concentrate) and direct a light source's output into a tight "spot," many of these LED bank lights already have a dispersed (even and somewhat devoid of a "hotspot") output. Some of these lights place the LEDs 10-15mm apart for greater dispersion. The problem with the use of low-power, 5mm LEDs placed further apart is that the overall output, while dispersed for soft, even lighting, is LOW.

    I prefer multi-die, high-power LEDs spaced closely so that more LEDs can be used in a smaller package. The Cineroid product has an approximate 120-beam spread. If I want to soften (diffuse) the product light output, I use a diffusion sheet or panel.

    "Quick and dirty" light product output measurement using a 10-inch integrating sphere reveals that my Cineroid light is outputting 350 lumens with an estimated +/-5 lumens measurement uncertainty at 2-Sigma at full or max setting with a freshly-charged battery.

    Without having executed a controlled design of experiment (DOE) utilizing NIST-traceable, calibrated instrumentation, I estimate a Color Rendition Index (CRI) of 80-85 for the Cineroid product based on my education and several decades of experience.
     
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  5. addieleman

    addieleman Mu-43 All-Pro

    Aug 5, 2010
    The Netherlands
    Ad
    So it seems a quality unit will cost more than $200 and I think I need 2 of them. Maybe I'll go for halogen lighting instead, much cheaper solution probably for lighting with good colour balance.

    Thanks for the warnings, I have a better idea now where to watch for.
     
  6. 0dBm

    0dBm Mu-43 Top Veteran

    859
    Jun 30, 2011
    Western United States
    A halogen light source will provide better CRI; however, it will generate quite a bit of heat and the bulbs have a much shorter life. There is always a tradeoff with anything. Good luck.
     
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