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URGENT!! 45 degrees shutter angle question


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#1 Christophe Collette

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Posted 30 June 2007 - 11:16 AM

Hi there, I have to do a reshoot for a hip hop video that a friend of mine shot two days ago, he shot the whole thing at 45 degrees shutter angle on a 435, he had a 4k on a 12000w genie, the whole thing flicked... He had a magnetic ballast for his 4k... An error from the rental place, he asked for a ff ballast. Production went on, they were on location, far from the rental place. Anyway, here I am, reshooting for him since he is gone to other business, I have a continuity issue to deal with, that 45 degrees look, but I am a bit concerned since I never shot 45 degrees before. All I have for lighting are two kinos on a small genie, since kinos are flicker free, I should be fine at any shutter angle, but I'd like someone to reassure me, I am shooting this in three hours, just learned about it...

Exposure correction is two stops, am i right???

Thanks for helping me out,


C
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#2 Kieran Scannell

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Posted 30 June 2007 - 12:18 PM

Christopher,

2 stops is correct, but don't you have more continuity problems in terms of lighting if you only have 2 Kino's?

Good luck!

Kieran.
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#3 Christophe Collette

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Posted 30 June 2007 - 12:37 PM

I know, the company does not want to go through insurances to reshoot, they are paying for the reshoot therefore they are super tight on budget... I would have much preferred a 4k than two kinos but they made the list, and I stick with it. Do you have any experience shooting 45 degrees with kinos, I am guessing it should be fine, since kinos are ff, but I never shot 45 degrees before so I prefer asking before....

Thanks a lot.

Christophe
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#4 Andre Szankowski AIP

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Posted 30 June 2007 - 12:54 PM

Hi Christophe, you won't have any problems shooting 45 degrees with kino fluos. 180, 90 , 45 degrees are safe angles for Kino Fluos. You only get Kino problems at higher camera speeds and if the ballast is malfunctioning.
Good luck!
Andre
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#5 Kieran Scannell

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Posted 30 June 2007 - 12:58 PM

Christophe,(got it right this time!)

just shoot as you would normally and you'll be fine! I just feel 2 kino's as a complete lighting kit is a bit flimsy you've got
no punch if you know what i mean? I've never shot a 45 degree shutter angle before, never had reason to, stylistically or
other. I wish i could help you more, are you operating as well?

Best of luck.

Let me know how it turns out!

Kieran.
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#6 Andre Szankowski AIP

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Posted 30 June 2007 - 01:05 PM

if you are really stressed with this situation, because you didn't have time to test it , just say you don't have enough light with two kino fluos to shoot at 45 degrees, it will not match the previous material anyway, not only the difference with the material available to you, but also, because you didn't prepare it, scouted it(i'm assuming) and you're not in your friends head to think about the lighting the same way he did. Just propose to do the best you can, with what you have, i mean, a hip hop music video does have room for different looks.
All the best!
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#7 Christophe Collette

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Posted 30 June 2007 - 01:33 PM

I borrowed a 1.2k HMI Par with FF ballast from a gaffer I know, I plan on bouncing it into a 8x8 silver lame pretty close to my subject, should pretty much give the same output as the 4k diffused heavily, it's going to be harsher but I'll have the broadness at least...

Will I be alright with HMI with a ff ballast on a 2k genie for 45 degrees shutter angle???

I saw the transfert from the other dp's stuff, the footage that flicked, I think I can manage with the 1.2K HMI....

He went down to 11 degrees, the flicking was really slow, kind of like when you put a lamp behind a fan turning pretty slowly, I actually thought it looked quite cool!

I think it was pretty risky for him to shoot such weird angles on a genie with no ff ballast... He is a very experienced dp from out of town, they flew him in for the gig, he is so booked up that there was no way he could come back to reshoot.... You would imagine that with that level of experience, he would not make such mistakes.... Well... Anyway, what's done is done. Gotta fix things up now!


Thanks guys, I'll let you know how it went.

C
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#8 David Mullen ASC

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Posted 30 June 2007 - 05:51 PM

The problem with a 45 degree shutter and an older magnetic ballast is generally not flicker, but inconsistent exposure. At a 45 degree shutter, 24 fps, you are exposing less than a full sine wave of the light output. So depending on whether you catch the wave at its peak or valley and then fall in sync with that, your overall exposure may be normal or dimmer than it should be.

With a high-frequency ballast, you have a lot more pulses to capture even with a 45 degree shutter.
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#9 Jim Feldspar

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Posted 30 June 2007 - 06:37 PM

The problem with a 45 degree shutter and an older magnetic ballast is generally not flicker, but inconsistent exposure. At a 45 degree shutter, 24 fps, you are exposing less than a full sine wave of the light output. So depending on whether you catch the wave at its peak or valley and then fall in sync with that, your overall exposure may be normal or dimmer than it should be.

With a high-frequency ballast, you have a lot more pulses to capture even with a 45 degree shutter.



I know that you must know, but I thought that flicker is inconsistent exposure,
caused by the flickering light causing some frames to receive more or less light.


Good luck, Christophe!
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#10 David Mullen ASC

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Posted 30 June 2007 - 06:49 PM

I know that you must know, but I thought that flicker is inconsistent exposure,
caused by the flickering light causing some frames to receive more or less light.


Flicker is inconsistent exposure frame to frame -- what I'm describing is an overall exposure change each time you trigger the camera, consistent within the take, but inconsistent take to take.
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#11 Tony Brown

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Posted 01 July 2007 - 02:29 AM

Who is this production company that does your 'list' for you? A couple of Kino's when dealing with a 2 stop loss? Not too smart are they......
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#12 Jim Feldspar

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Posted 01 July 2007 - 01:15 PM

Flicker is inconsistent exposure frame to frame -- what I'm describing is an overall exposure change each time you trigger the camera, consistent within the take, but inconsistent take to take.



Vey clear now. Good distinction to know. Thanks!
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