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#1 Alex Haspel

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Posted 24 January 2006 - 03:49 PM

i'm not sure if those things are called like that in english too, so here's a picture for safety reasons:
Posted Image

does anybody know if those are flickerfree at all speeds or only at 25fps with 50hz electricity network?

thanks in advance,
alex
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#2 Laurent Andrieux

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Posted 24 January 2006 - 03:59 PM

I would not trust those but at 25 fps with 50 Hz supply.

One thing you can do as to make sure : take a video camera, set it at 1/60 s and look carefully if you see a color change.

If it slowly goes to green then magenta you have a valuable answer...
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#3 John Pytlak RIP

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Posted 24 January 2006 - 04:46 PM

You can run a camera test. Or hook a silicon photocell to an audio amplifier to "listen" to the frequency of the flicker. If it is 50Hz or 60Hz power line frequency "hum", they are not "flicker free". If it is a high frequency (> 400 Hz.), you likely will not see flicker at normal frame rates.

Note that the phosphors used in those lamps are more often chosen for high luminous efficiency rather than good color rendering, so you may have fun finding a filter that give reasonable color reproduction.
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#4 Stuart Brereton

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Posted 24 January 2006 - 04:56 PM

Note that the phosphors used in those lamps are more often chosen for high luminous efficiency rather than good color rendering, so you may have fun finding a filter that give reasonable color reproduction.


Every lamp of this type I've ever shot has been VERY green. Not the blue-green you get from fluorescents, more of a bright yellow/green.

Maybe they've improved recently, but I'd advise you to test.
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#5 Laurent Andrieux

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Posted 24 January 2006 - 05:02 PM

hook a silicon photocell to an audio amplifier to "listen" to the frequency of the flicker. If it is 50Hz or 60Hz power line frequency "hum", they are not "flicker free". If it is a high frequency (> 400 Hz.), you likely will not see flicker at normal frame rates.


Excellent !

Say, I can't find the "amp out" socket on my lightmeter, John, do you know where it is ? :lol: :lol: :lol:

So sad... I think I'll just plug my electric guitar instead, just to see if it's flicker free !!! :rolleyes:
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#6 Matt Sandstrom

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Posted 25 January 2006 - 06:18 AM

they are driven by a high frequency ballast, but i think the line frequency leaks through. i'm basing this on the fact that they sometimes flicker while the 12 volt ones don't. are you using them to illuminate the scene or are they just in the frame?

/matt
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#7 Phil Rhodes

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Posted 25 January 2006 - 06:41 AM

Hi,

Careful.

12 volt fluorescent tube drivers will almost invariably be flicker free as they're usually self-resonant choke designs. This does not mean that a mains fitting that happens to look the same will be.

For what it's worth, I've found that those things tend to have a much better chance of being flicker free than normal fluorescent tubes, at least until recently, but there's no guarantee either way. I've seen both types.

Personally I can tell what it's likely to be by inspecting the ballast design, but that would require some familiarity with high frequency magnetics and you can't usually get at the drivers in those without breaking the case.

Phil
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#8 John Carreon

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Posted 25 January 2006 - 06:55 AM

True...but who isn't familair with with high frequency magnetics?

Man, I feel so dumb at times...

John
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#9 John Pytlak RIP

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Posted 25 January 2006 - 07:03 AM

True...but who isn't familair with with high frequency magnetics?

Man, I feel so dumb at times...

John


Again, "listening to the light" with a silicon photocell connected to an audio amplifier works well as a quick test with unknown lights. Any light flickering at the line frequency will produce a hum, higher frequencies will be heard as such. Light a match near the cell and you will hear a "whoosh" sound. "Hearing light" is the same principle used for analog optical soundheads in a projector -- when I worked as a theatre projectionist, you needed to be careful not to let your worklight shine onto the photocell in the projector while it was running, or the audience would hear the hum.
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#10 Preston Herrick

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Posted 25 January 2006 - 12:30 PM

I used a pair of them once with a power inverter (24fps, 60Hz) to light a car interior. There was no flicker and the film was telecined with any green corrected out - and there wasn't a lot to begin with.

Edited by PrestonHerrick, 25 January 2006 - 12:31 PM.

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#11 Laurent Andrieux

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Posted 25 January 2006 - 03:31 PM

"Hearing light"


I love that !!!
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#12 Michael Collier

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Posted 25 January 2006 - 09:10 PM

Dont use them. Thats my advice.

They may flicker, may not. I dont care, they look like crap most of the time. And not even that kind of crap you can pass off as art, they just look bad.

The color is way off on them, for most of them even farther than normal cool whites, even when you buy the 'tungsten' balanced versions. You may go mad trying to find filters that render pleasing tones, or you may just end up not testing and hopeing, which is much worse.

The other question I had was why are you so eager to use them? Any particular reason. If ugly color is what your going for, for accent lighting or horor film lighting, then maybe they would work, but in general they look awful (and not one kind of awful, there are 3 different kinds I have encountered. probably 2 cool white versions and a tungsten that looked nothing like tungsten, even to the bare eye. Im sure there are more variencies in photon chemistry making them even more unpredictable.)
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#13 John Pytlak RIP

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Posted 26 January 2006 - 06:58 AM

I "listened" to the light from a dozen or so different "compact flourescents" I have in my house. ALL of them had a very strong 60Hz line frequency "buzz" and nothing of a higher audible frequency. I suspect they would have some degree of flicker propensity, and need to be treated just like regular flourescents on an inductive ballast.

The color rendition is usually quite "ugly", tinged with a yellow-green, compared to flourescents (e.g., Kino-Flo) having a higher color rendering index.
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#14 Alex Haspel

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Posted 26 January 2006 - 08:27 AM

thanks a lot, to all of you!

i asked this question because the director on a 16mm short i am Dp'ing on wanted to use one of those things.
the piece will be entirely lit with practicals, shot on 7279 and a 16bl with zeiss high speed primes.
and there will be one scene were flickering would even be quite nice...

as i already said, thank you all very much...
and.. if you have any tips to share concerning shooting entirely with practicals, feel free to do so!
about the visual style... it's gonna be all indoors and extremely dark. i plan to expose for the lighter parts and let the rooms drown in black, using no fill at all.
unfortunately we had no money to shoot any tests... but i'd say lens flares are quite an issiue, aren't they?
but i suppose there isnt anything to do about that.. since practicals have this habit of sometimes beiing in the frame...
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#15 Chris Sharman

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Posted 26 January 2006 - 10:12 AM

Out of interest, can you use this kind of bulb on a dimmer?

JM
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#16 Jonathan Bryant

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Posted 26 January 2006 - 01:04 PM

Out of interest, can you use this kind of bulb on a dimmer?

JM

Nope unless you want it to flicker. I have used these at my house and also have wondered how good their color rendition is. To my naked eye they didn't look that bad, but not true tungsten.

Do they have a CRI rating?
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#17 Freya Black

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Posted 28 January 2006 - 05:03 PM

Nope unless you want it to flicker. I have used these at my house and also have wondered how good their color rendition is. To my naked eye they didn't look that bad, but not true tungsten.

Do they have a CRI rating?


Strangely I have shot under compact flourecants here in the u.k. with an ntsc camera and there was no flickering. Under normal strip light flourecants there was flickering like crazy with the same camera.

Can't comment on colour temp as I was shooting in black and white.

Not sure if this really tells you anything...

love

Freya
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#18 John Pytlak RIP

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Posted 28 January 2006 - 09:27 PM

I had a chance to "listen to the light" of a few of the battery-operated fluorescents, and they all had a high pitched whine, rather than a 60Hz buzz. Likely the battery-operated ones won't cause flicker.
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#19 Werner Van Peppen

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Posted 05 February 2006 - 05:55 PM

Strangely I have shot under compact flourecants here in the u.k. with an ntsc camera and there was no flickering. Under normal strip light flourecants there was flickering like crazy with the same camera.

Can't comment on colour temp as I was shooting in black and white.

Not sure if this really tells you anything...

love

Freya


Most modern fluorescent lightfittings use electronic ballasts nowadays to improve their efficiency. Especially in office buildings the power savings can be quite big. Shot recently a short where the entire floor was lit by electronic ballasted flos and would dim/fade out if the heatsensor wasn't activated for about 5 minutes. A quick wave and it would gently fade in. Interesting effect.


Strangely I have shot under compact flourecants here in the u.k. with an ntsc camera and there was no flickering. Under normal strip light flourecants there was flickering like crazy with the same camera.

Can't comment on colour temp as I was shooting in black and white.

Not sure if this really tells you anything...

love

Freya


Most modern fluorescent lightfittings use electronic ballasts nowadays to improve their efficiency. Especially in office buildings the power savings can be quite big. Shot recently a short where the entire floor was lit by electronic ballasted flos and would dim/fade out if the heatsensor wasn't activated for about 5 minutes. A quick wave and it would gently fade in. Interesting effect.
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