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Lighting for High fps video (FS700, LX7, Phantom)
  • Since high fps video is finally in our price range, I have been researching various methods to avoid flicker.

    1, Shoot outdoors with pure sunlight. This is the easiest setup and there will be no flicker at all.

    1. Indoors are a big problem. All lights flicker under ac. Here is an excerpt from the makers of the Phantom cameras..

    When powered by alternating current (AC) electricity, the lamps power cycles 50 or 60 times per second (depending on the country and its power system). During the down cycle the tungsten lamp filament can dim slightly. Above certain frame rates a camera sensor is photographing enough images per second to see the alternation of the filament, resulting as flicker in the image.

    The amount of flicker is related to the type of bulb, wattage and physical size of filament. In general, lamps of 5000w or larger that use tungsten filaments are so large that they do not have time to cool and dim before the power cycles back up. Therefore, it is recommended using 2K or greater tungsten light fixtures when shooting above 120fps in 60hz countries and 5K or greater when shooting above 100fps in 50hz countries.

    Some additional recommendations are to use DC power for tungsten lights, which eliminates flicker entirely. The direct current supplied to the lamp head means there is no alternation between cycles and the filament is illuminated constantly. Smaller practical bulbs can be battery powered thus avoiding flicker issues.

    HMI and fluorescent lights are generally fine for speeds under 100fps as long as they use electronic ballasts and are set to flicker free. Although HMI lights do not suffer from the flicker which effects tungsten, HMI’s can suffer from “Arc Wander,” whereby a plasmatic “hot spot” moves within the bulb, causing an amorphous shifting movement in the light output. The most common side effect to this is a rapid colour shift in a shimmering effect. No HMI light with a normal electronic ballast can be guaranteed against some form of flicker, no matter how big the lamp is.

    In recent years high frequency ballasts have been produced for HMI lamps. In the UK, Panalux stock 300Hz ballasts for HMI lamps between 125W and 18,000W. Similarly Arri has produced 1000Hz High Speed Ballasts for use with the same HMI lamp from 125W up to 6000W. These ballasts dramatically reduce or even eliminate flicker in most situations, but under practical use of these tools, it has been found that in certain lighting conditions and with certain lamps and bubbles, flicker still may be apparent. Testing of the specific lamps to be use on a job is always advisable.

    LED lights are subject to the electronic circuits driving them which can create a vast array of refresh rates, but generally LED fixtures designed for the film industry will not flicker as long as they are not dimmed. In recent times, more and more LED lights are becoming available for motion picture, many of these are now being commonly used for high speed shooting.

    Finally, the shutter angle on the high speed camera can affect flicker as well, as a greater shutter angle allows for a longer response time from the light. When shooting extremely high frame rates, it may no longer be necessary to retain a 180-degree shutter to capture the motion generally preferred for a filmic look. A 360-degree shutter allows both more light sensitivity and can reduced flicker possibilities.

    Lighting with HMI’s

    HMI lighting that uses electronic ballasts will not flicker, but they can be prone to another artifact. This would be Arc Wander, as described in the previous passage, the hot spot of the electrical arc that travels in the plasmatic gas within the glass bubble moves back and forth between the two cathodes. The resulting effect appears as shimmer and colour shift.

    If one big light is used directly pointed at the subject, this effect can be quite obvious. If many lights are mixed together or if the light is punched through diffusion then Arc Wander can often be limited to an unnoticeable level.

    With the 300Hz and 1000Hz High Speed Ballasts it is possible to achieve high quality flicker free images at frame rates of 1000 fps and in many cases beyond even with a single HMI daylight source.

    This new technology supplies the lamp with a greatly raised square wave current rather than the typical 75Hz. High frequency ballasts are available for all wattages from 125 W – 4000 W. It is recommended to test the lamps at the shooting speeds required prior to a job.

    Tips for lighting with HMI’s

    Test your fixtures before shooting
    Obtain 300Hz or 1000Hz ballasts
    Use as bigger sources as possible
    Use diffusion or bounce the source
    Group smaller heads together separated by different phases
    Using HMI’s when shooting outside is much less noticeable than when inside
    Often changing the head or the ballast can help any issues
    Make sure the electronic ballast is set to flicker free
    
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  • Now lets add different types of lighting with zero flicker. So we can have DC lighting only - either LED or tungsten/HMI.

    Here is a test of LED lighting vs fluoro

  • On Ebay, High Power Stage lights seem to come in 3W and 5W increments. In sets of 36, 54, 72 and 108 for 3w. In sets of 90 and 120 for 5W.

    75W approx equates to a throw from a 500W tungsten.

    There is a High Power 36x3W RGB LED model. When you fire all the RGB LEDs, thats 108W. If do not dim them, there will be no flicker.

    So, there are 36x3w, 54x3w, 72x3w and 108x3w models.

    The page for Guangzhou Eagle http://www.aliexpress.com/store/group/Led-Par-Light-Series/711949_211612531.html

    440/- for 108x3w http://www.aliexpress.com/store/product/108-3W-Led-Par-Light/711949_568942797.html

    Other manufacturers with a better price perhaps..This light has adjustable beam angle for narrow, medium and wide flood.

    http://nebulalight.en.alibaba.com/product/483619096-212739175/New_Design_108_x_3W_RGBW_LED_Par_Washer_Light.html

    http://www.aliexpress.com/product-gs/442710986-Edison-LED-3W-108-Pcs-Moving-head-Led-Stage-light-wholesalers.html

    The 90x 5W and 120x 5W lights are made by MS Lighting in Guangzhou. They have not posted their prices anywhere.

  • Very interesting. Thank you for your information. Thats why i preffer tugnsten, more old school.

    Cheers.

  • A video that I was hoping to use in my film. Completely unusable at the moment..Lit with just a 1000w MFL PAR64 on top. You can see fluoro flicker as well as Tungsten flicker. The shadows also affected my ability to use effective Optical Flow based slow motion

  • Hmm. There is an inconvenient but effective option to get rid of tungsten flicker, which is put more than one light of the same size each on a different phase of your power system, so the the dim moment of one light is synched up with the bright moment of the other light(s). You will probably want to merge the beams by putting them through the same piece of diffusion. Not convenient to do. IF you've got a tie in or a generator where you know what phase is what, you've probably got the money to get 5ks.

    On your video, I dodn't think the overhead PAR looked bad. I have actually been fine shooting with 1k VNSP PAr-64s with a Phantom at 500 and 1000 fps. (on AC 120v power) I was surprised that there was no issue, actually.

    The fluorescents? No help to offer there. I just don't use them on high speed work, although kino flo ballasts ought to work fine, since they are super high freq ballasts. Were the fluoros in the background just regular commercial fluorescents?