High-speed lightning & tungsten

[samuel valkola]

Hello!

 

I'm shooting a short film next week and I'm going to use a lot of high-speed cinematography. It would be possible to use 300w tungsten lights (dts par 56) for free. I'm wondering about the flicker issues. How many frames per sec can I capture before the flicker comes visible.

 

Thanks in advance,

Samuel

[samuel valkola]

I will be using Sony F700.

[David Mullen ASC]

Somewhere in the 200 to 300 fps range you'll probably see some flicker from using 1K globes, 300w globes would be even worse to use, but you might be fine below 200 fps. Or maybe not (test!) Ideally use flicker-free lights instead or 2K globes if not 5K as you go even higher than 200 fps. Here's some text I found online from the folks at Phantom:

 

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, HMIs 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.

[Leonardo Brocato]

I worked many times with the phantom, high speed lighting it's hard, with the phantom sensor any lamp equal or under 1k included par64, quartz redhead or fresnels flicks, but we are talking about more than 500fps.
I think with the sony fs700 up to 200fps you cannot see anything, you can also diffuse a lot or bounce, reducing flicking in the hot spots, You HAVE to make a test but after decided at what frame rate. I think par 56 are not so good for high speed.
Shoting at low shutter angles also can create problems but in high speed you can expose also for 360°

I'm curious about this sony everyone say it's very good in high speed.
Last time we used a lot of Arri T12 fresnel tungsten, a lot, 8 in a kitchen 5 direct, 3 bounced plus more 5k and 4 eroic blondes up the fire of the cookers that ends a 12 hour shoting undamaged.
Let us know something more about this Sony

Leonardo Brocato
Gaffer Rome Italy

[Maximilian Hillmer]

which also depends on the power frequency from that you'll shoot.

In European countries with 50 Hz and 240 volts you will need with a lower wattage longer time to reach the limit of flicker.

Now if you're shooting in America with a 60 Hz frequency at 120 volts you quickly pushes to the limit.

[Maximilian Hillmer]

http://upload.wikimedia.org/wikipedia/commons/f/f5/Weltkarte_der_Netzspannungen_und_Netzfrequenzen.svg

[Leonardo Brocato]

 

which also depends on the power frequency from that you'll shoot.

In European countries with 50 Hz and 240 volts you will need with a lower wattage longer time to reach the limit of flicker.

Now if you're shooting in America with a 60 Hz frequency at 120 volts you quickly pushes to the limit.

 

In my experience it's not a question of load, with 50 or 60hz it's only a question of multiple, up to 120 in the us the sensor can capture the up and down of the incandescence of the filament, bigger is the filament (5k and more) lower it's the period of low incandescence. With dynos for example you have a lot of light but the par filament will flick in every bulb.

In 220V the only better thing it's you "waste" less ampere, but not less watt.

I'm very courious about that i've tested both sistems but i'm still thinking that can be some differences in the tipe of light, due to 110v and 220 not only in the ampere.

 

 

[Maximilian Hillmer]

yeah in my experience there is a little difference. I've done a small test because of a shoot in a 60Hz country and in the higher fps area the ccd sensor is more sensitive to flicker in a 60hz frequenz compared to a 50hz. anyway i don't tested cmos but fluorescent lighting and there is a hugh problem with ccd and flicker for example.

[Mark Dunn]

From memory, blondes are fine for scientific purposes at 10,000pps. Might not be good enough for drama.

[David Mullen ASC]

From my experience with the Phantom at 1000 fps, you need to use a 5K at the smallest, a 2K bulb is pushing your luck. Of course, this is with AC power.