7 replies to this topic

[Daniel Miler]

Hi all

 

All though this topic appeared several times before, I havent been able to find specific enough info on the subject.

 

I am shooting a night scene in a forest, and plan to light it only with the light coming from two practical flashlilghts carried by the main characters (apart from very low-key HMI light for ambiance). I will be shooting on the alexa, and hope to acheive a T stop of about 2-2.8. How much Lumens do I need these flashlilghts to be? is 500 Lumens enough? do I need much more than that? 
I also plan to color the flashlights with Storaro Yellow jel which will take up some light...

[Phil Rhodes]

It depends what you're trying to illuminate and how far away it is, as with any light source.

 

You can get LED flashlights with quite high output, or if you need more, there are types based around discharge lights available in (at least) 35 and 85-watt varieties which should be enough for anyone.

 

P

[David Mullen ASC]

Just find really bright flashlights, you can always knock them down.

[John E Clark]

Hi all

 

All though this topic appeared several times before, I havent been able to find specific enough info on the subject.

 

I am shooting a night scene in a forest, and plan to light it only with the light coming from two practical flashlilghts carried by the main characters (apart from very low-key HMI light for ambiance). I will be shooting on the alexa, and hope to acheive a T stop of about 2-2.8. How much Lumens do I need these flashlilghts to be? is 500 Lumens enough? do I need much more than that? 
I also plan to color the flashlights with Storaro Yellow jel which will take up some light...

 

Using 'lumens' is some what difficult to deal with when estimate 'how much light falls on a particular area'. The reason for it is that the lumen output is usually in terms of the total light 'beam'. So for a flash light beam of say 45 degrees those 500 lumens are spread across such a cone of light. (not to mention some manufacturers just go from 'fundamental principles' rather than actual measured output of their device...)

 

For Israel, and the rest of the world, the unit of measure to be concerned about is lux, in the US it would be footcandles. This is 'how much light is falling on a particular point'. And is also what meters are calibrated to for reading out the exposure.

 

Unless the flashlight has a data sheet that lists lux/fc at various distances, you really have to emperically measure it. So, at night, with a light meter that reads out in lux/fc, and some measured distances, you can determine whether there is enough light for your needs.

 

As for 'night', no matter what the output of the flashlights are and even with some 'low light fill', there are going to be large areas of 'black', in a 'forest' situation. I have read that the Alexa's 'natural' ISO is 800, and I have read some times people go up to 1280 or even 1600. This of course is better than most Film film, but still if you don't want 'blank' blacks, that perhaps shooting just after sun set, would allow for more illumination of the 'background' if that is desired...

[John Miguel King]

I have read that the Alexa's 'natural' ISO is 800, and I have read some times people go up to 1280 or even 1600.

On a sidenote, Topboy season 1 was shot on Alexa at 2000 ISO most of the times and it looks unbelievably awesome.

[John E Clark]

On a sidenote, Topboy season 1 was shot on Alexa at 2000 ISO most of the times and it looks unbelievably awesome.

 

Well... just the time I go a bit conservative... someone comes along and tells me I'm being a stick in the mud...

 

I recently did a shoot with a Canon C100 @ ISO 3200. I was worried about 'noise', since I had no time to 'test'... but I did light the talent for what I thought was a reasonable level, and when I pixel peep on the dark wood paneling in the back ground I can see 'some' noisy pixels.

 

But otherwise I was fine with the results. But I do advocate testing things before hand, so I would not advocate shooting the C100 that ISO unless someone tests and deterimes it works for their needs.

Edited by jeclark2006, 28 August 2014 - 11:32 AM.

[Satsuki Murashige]

 
Well... just the time I go a bit conservative... someone comes along and tells me I'm being a stick in the mud...
 
I recently did a shoot with a Canon C100 @ ISO 3200. I was worried about 'noise', since I had no time to 'test'... but I did light the talent for what I thought was a reasonable level, and when I pixel peep on the dark wood paneling in the back ground I can see 'some' noisy pixels.
 
But otherwise I was fine with the results. But I do advocate testing things before hand, so I would not advocate shooting the C100 that ISO unless someone tests and deterimes it works for their needs.

Yes, the C100 is a great documentary camera but for my taste I've found it to be noisy in the shadows when underexposed, even at 850 ISO. Probably the 24mbps codec. Very nice images otherwise though.

[Daniel Miler]

 

 

lumen output is usually in terms of the total light 'beam'. So for a flash light beam of say 45 degrees those 500 lumens are spread across such a cone of light. (not to mention some manufacturers just go from 'fundamental principles' rather than actual measured output of their device...)

thanks all

 

very interesting facts about Lumens Jeclarck2006. 
Guess Ill just have to stop being a lazy bastard and test some actual flashlights with a light meter. I was hoping to just drop a Lumen minimum demand on the art departement and leave it at that... 

 

As for ISO, you may call me old-fashioned, you may call me chicken poop, but I never dared go beyond 1,600 with the Alexa....