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Pentax spotmeter questions

spotmeter ev footcandles

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#1 Geoff Smith

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Posted 09 June 2017 - 07:57 PM

Hi,

 

I just got a Pentax Digital Spotmeter and am trying to work out how to use it for motion (other DPs I know swear by them). Do I have this roughly right?:

 

     15 footcandles = EV 6 = T2.8/4 split @ ISO800, 24fps, 180º shutter

 

So I would want a gray card to give me ~EV6 back on the meter and then I would adjust the overall ratio to not exceed the camera’s usable dynamic range (and be appropriate for the scene/subject/project of course). If I want to overexpose by 1 stop then I would 2x the light to EV 7. Does that math work? How do people use these in practice?

 

I’ve noticed with these that if you line up the motion shutter speed tick mark along the centerline, you get an ISO/ASA of 160. Am I better off lining up on the motion shutter speed and doing the 2.33 stops math in my head (if I am shooting at ISO 800, the base/native ISO of many cinema cameras) or should I leave ISO/ASA 800 lined up on the meter and work it out the other way? Is it just a matter of what feels more natural? Thanks for any insights...

 

--Geoff


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#2 John E Clark

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Posted 13 June 2017 - 11:38 AM

I use a combination of a incident meter for measuring the amount of light falling on the scene, in terms of footcandles. Since motion pictures requires more light in general, than one can 'get away with' for stills (like set the shutter for 1/2 second if need be...) I like to make sure I have enough light for a basic exposure.

 

I use my spot meter for detailed scene contrast ratios, especially the faces of the talent, or various hot or 'dark' spots in the scene, to see if the range will fit, or at least to expect blown highlights or dark shadows, as I don't have too much in the way of artificial lights to compensate.

 

I did try to come up with some formulaic transformation from 'grey card' relectance -> EV -> footcandles... but it was just easier to get a meter that read out footcandles directly.


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#3 Geoff Smith

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Posted 13 June 2017 - 03:29 PM

Thanks much for the detailed answer John! I think I'll follow your example and start by experimenting with it along with my trusty Spectra IV-A and use the spot meter to understand where various parts of the scene will fall relative to middle gray.


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