Fluo Flicker on Fulham Workhorse Ballast

[DaneCannon]

I built a 4 foot 4 bank of fluos and replaced the magnetic ballast with a Fulham Workhorse Ballast. Though the scrolling horizontal lines of darkness are less pronounced, I still see them. I check by stopping down and lensing the bulbs themselves. I'll tilt the camera up and down to check and see if there is a pattern that moves with the camera (as opposed to staying with the image). What shutter speeds have other DIYers found to be acceptable with these ballasts? Also, what shutter speeds/angles are okay with Kino Flos?

 

[DaneCannon]

From Guy Holt... on several posts across several boards
"There does not appear to be any truth to that statement either. You get what you pay for. Inexpensive high frequency fluorescent ballasts can have another type of flicker problem called an “eratz ripple.” Even though the ballasts put out a high-frequency cycle, that cycle stacks to create a lower frequency waveform which causes the light to pulsate. In a number of incidents, 24p video cameras and film cameras operating within a flicker-free window have picked up flicker from the “eratz ripple” effect. When making your own fluorescent soft banks or using solid-state high frequency ballasts for built-in set practical fluorescent light fixtures, it is necessary to shoot tests with the ballast you plan to use to make sure you will not get an “eratz ripple.” 
Kino Flo fixtures, on the other hand, use high frequency electronic ballasts that run at specific high frequencies that eliminate the generation of an “eratz ripple” (most at 25 kHz , the Parabeam Light at greater than 30 kHz) resulting in flicker free operation at any frame rate or shutter setting. Kino Flo ballasts also incorporates advanced electronic circuitry so that they will ignite a lamp instantly, even when cold, requiring no warm up time."

Incidentally, it's not called an eratz ripple, but an ersatz ripple (see Set Lighting Technician's Handbook)...

Anyway, while this does seem to be an issue close up to the light source, it seems to be mitigated somewhat further away from the light source, I'm guessing because of the light bouncing all around and thereby upsetting the frequency? Any thoughts on this?

 

[treynolds]

i have found that slower shutters work better to help reduce this effect. If i shoot at 50th in my country technically i shouldnt see any banding or as i now know its called ersatz ripple. I have found however that if i stop down one or two more stops i get far less and it becomes very useable. The problem then becomes the amount of blur in each frame becoming unacceptable on anything with much motion at all. That is what i have found with cheap ballasts. I have also found the same results when i am getting strobbing from LED stage lights. Lower shutter speed = less strobe.

 

[bruce southerland]

When I built my flos, I sent Fulham the Kino specs for the bulbs I wanted to drive, & they recommended a ballast.
my lights are flicker free at 1/24, 1/48, 1/60, & 1/120. You may want to do the same.

 

[Deer Film]

Hi Bruce, how much where the bulbs that you got if you don't mind me asking.
Thanks

This week I am going to try Menards t8 bulbs in a shoot.
I am using Joe Edelman's idea http://www.youtube.com/watch?v=OBPDSBCoN2c&feature=youtu.be
I have to shoot a training seminar down in the basement of a school. So I need a lot of my own light. To go with Joe's idea, it should work and save money.

 

[wangtrirat]

For problem on Ballast that I used. If you use Electronic ballast and experienced flicker, This is solution. (Danger!!!! electrician skill required.)

EB operated at >15KHz many of these mostly operated at 20KHz+. But Where is the hell that flicker came from?

Circuit have to transform AC to DC which it'll use Bridge Rectifier and output is DC approximately about 400v or using 200v for 2 in series, you'll see the largest capacitor on circuit. It did the job for smoothing the electric flow but some how it's too small.

The blue component on this ballast is Capacitor.

50Hz (in my country) override smooth 25KHz operating Frequency of Ballast result in Banding on Shutter Speed over 1/250.

How to solve that? Very simple answer = Bigger Cap. to smooth out all that shimmering current.

This is picture of Kino-Flo Ballast itself totally proved my idea. Big 2 390uf 200v cap in series.

I've use 470uF/400v cap for one 55W tube and result is fascinating. 1/4000 max of DSLR, No flicker or banding at all.

Notice : I've use expensive ballast before, problem still there. Recently I used cheap Chinese ballast but with modification of this solved all problem.

Hope this is helpful but again I've no responsibility for damage. Try at your own risk!!!!!!

If you have some suggestions please let me know.

Thank you.