ARRI 300 and CTB problem

[julien doumenjou]

Hi,

 

just shoot a scene in an office (med-shot) using daylight from window and 2 ARRI 300. There was enough light until I put the CTB on the ARRI (of course I had to do it for color balance). Is it my imagination or Arri 300 is really low using with CTB ? Unless used for close up ?

[Jeff Kolada]

full CTB takes a full stop of light away from anything you put it in front of. So usually if you're going to CTB a light, it should be twice as bright as you would have it without a filter, or closer to the subject.

 

I am assuming you're using full CTB.

 

FullCTB: 1 Stop Loss

HalfCTB: 3/4 Stop Loss

QrtrCTB: 1/2 Stop Loss

[Chris Keth]

full CTB takes a full stop of light away from anything you put it in front of. So usually if you're going to CTB a light, it should be twice as bright as you would have it without a filter, or closer to the subject.

 

I am assuming you're using full CTB.

 

FullCTB: 1 Stop Loss

HalfCTB: 3/4 Stop Loss

QrtrCTB: 1/2 Stop Loss

 

Full takes 1-2\3 stops. It felt like the light was low because it was! Your 300W was working as only about a 120 watt fresnel.

[julien doumenjou]

full CTB takes a full stop of light away from anything you put it in front of. So usually if you're going to CTB a light, it should be twice as bright as you would have it without a filter, or closer to the subject.

 

So I should have used a 650W instead of a 300 ?

[JD Hartman]

1/2 CTB would bring the color temp close enough, full CTB actually over-corrects.

[Brian Drysdale]

1/2 CTB would bring the color temp close enough, full CTB actually over-corrects.

 

Full CTB is, perhaps a little under a full correction to daylight, but close enough. 1/2 CTB is no where near a full correction to daylight. I know people use it, but it's a compromise for light output.

 

On the over correction front, it's full CTO that over corrects converting daylight to tungsten.

[Chris Keth]

So I should have used a 650W instead of a 300 ?

 

If you wanted similar output to the bare 300W, I would have used a baby and then had room to scrim it down if need be.