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I agree, a meter that reads foot-candles is indispensible because it enables you to set levels and balance your fixtures in advance. Like a game of 3-D chess, a DP can light an entire scene in his head using his mind’s eye. As a starting you need to choose the exposure of the key tone at the outset - say T5.6 for deep focus. Having chosen the exposure you can then calculate how many Foot Candles (FC) you need on different elements of the scene.

 

To figure out how many FC you need for exposure, all you need to know is that it takes 100 FC to get an exposure of 2.8 with an ISO 100 film with a 180 degree shutter at 24 FPS (1/50th of a second shutter speed.) If your digital camera is 2 stops faster than an ISO 100 film, you will need 100 FC to get a stop of 5.6. Once you know how many FC you need for exposure you can simply calculate how many FC will give you the effect you see in your mind’s eye. Of course, it helps to have done a lighting test of what effect over and underexposing a subject will give.

 

Having roughed out your style and light placement you can begin to set your levels and balance your lights based on lighting tests you have shot over the years. For instance, if your camera is two stops faster than an ISO 100 film, you will need 24 FC to properly expose your key tone (mid gray) at a T Stop of 2.8. 24 FC would then give you a “properly” exposed flesh tone on her. But this is a bar with subdued lighting, so you don’t want full exposure on her. You liked the feel of a half key (1 stop under) in your lighting tests so you would light her with 12 FC from a high frontal key. Again, because the scene takes place in the subdued lighting of a bar, you don’t want to over fill her. Going back to your lighting tests you like the look and feel of an 4:1 key to fill ratio so you would give no more than 3FC of fill light. You need to separate her from the dark background of the bar and so you might give her a backlight of 6 FC because that's what looked appropriate in the lighting tests to separate her hair color from a dark background without looking over-lit.

 

 

Let's see if I got the FC thingy.

 

You know that to get an exposure of T2.8 @100ASA / 24fps / 180ª you need 100FC of light, any light that gives that amount of power.

 

So, as you said: "If your digital camera is 2 stops faster than an ISO 100 film (400ASA, right?), you will need 100 FC to get a stop of 5.6" and "if your camera is two stops faster than an ISO 100 film (400ASA), you will need 24 FC to properly expose your key tone (mid gray) at a T Stop of 2.8. 24 FC would then give you a “properly” exposed flesh tone on her."

 

Now, does that mean that if you want to expose your key tone (mid gray) at T2.8 with 800ASA (3 stops faster than 100ASA) you need 12 FC???

And if you want to open your Tstop at T2, that's 1 stop faster than T2.8 and you will need only 6FC to expose your key tone (mid gray) with 800ASA??

 

If what I'm saying is correct.. then IT IS super easy to make all the maths in your head! Probably I'm totally wrong haha.

 

You only need to set your key T Stop, your ASA and the rest falls in place quite easily!

 

There should be a whole book on Footcandles for dummies! :D :D :D

 

Have a lovely day.

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...so I can keep my lighting ratios consistent.....

 

If that's all you need then maybe an old seconic studio delux like Adrian and others mentioned. In lower light, without the high slide (a little perforated metal square that controls light coming onto the meter's sensor disk), its showing foot candles. They have a slide set so that many of the film ASA/ISO will read as T stops on the scale. I like the L28-C2 version.

 

Many might enjoy talking about the relative uses of the incident vs spot meters etc. Might just need a skillful question.

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Yes

 

That's great!! Thanks David!

I think that it will take a little bit of time to get used to measure in FC but seems like a good thing to do.. as many of you have suggested in the past :D.

 

 

One can use the edit feature to indicate rather than replicate all that good shizle from Guy. Smiley face.

 

Doooone! :P

 

--

 

I have a question regarding FC.. well, I have a couple of them but let's start with the easiest one ha!

 

I just started measuring things in Footcandles around the house, there is nothing else shown on the screen, just the Footcandles.

 

I suppose that the lightmeter measures footcandles in an independent way as in it tells you the amount of footcandles that a light is giving regardless of any other settings that you might or might not know.

 

So, let's say that if the light coming from my living room window is giving 450FC, I will have to do the math to convert those FC into a tstop using the formula given (T2.8 @100ASA / 24fps / 180ª you need 100FC of light), right?

 

At the moment.. it seems like 100FC is a lot of light in the 800ASA world!!

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Assuming we are talking about incident metering. Others can say it better and give more detail, but, the fc is just a measure of the brightness or illuminance of the source. So many photons per second pass through an imagined surface.

 

100 fc at 1/50sec, 800ASA, is quite a lot of light today. Checking with that old sekonic meter and thinking of that formula, 3 stops, is T8.

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Let's see if I got the FC thingy.

 

You know that to get an exposure of T2.8 @100ASA / 24fps / 180ª you need 100FC of light, any light that gives that amount of power.

 

So, as you said: "If your digital camera is 2 stops faster than an ISO 100 film (400ASA, right?), you will need 100 FC to get a stop of 5.6" and "if your camera is two stops faster than an ISO 100 film (400ASA), you will need 24 FC to properly expose your key tone (mid gray) at a T Stop of 2.8. 24 FC would then give you a “properly” exposed flesh tone on her."

 

Now, does that mean that if you want to expose your key tone (mid gray) at T2.8 with 800ASA (3 stops faster than 100ASA) you need 12 FC???

And if you want to open your Tstop at T2, that's 1 stop faster than T2.8 and you will need only 6FC to expose your key tone (mid gray) with 800ASA??

 

If what I'm saying is correct.. then IT IS super easy to make all the maths in your head! Probably I'm totally wrong haha.

 

You only need to set your key T Stop, your ASA and the rest falls in place quite easily!

 

There should be a whole book on Footcandles for dummies! :D :D :D

 

Have a lovely day.

 

I learned how to use foot-candles by using the meter most DP's were using when I was just starting out.

 

https://www.ebay.com/itm/SPECTRA-P-251-PROFESSIONAL-CINE-LIGHTMETER-ASA-SLIDES-ORIG-CASE-UNUSED-TESTED/132744643142?hash=item1ee8328246:g:kuwAAOSw1-dbcxJ5

 

You have to change slides when metering your key light or what you want to expose at, but then use foot candles for the rest. there is something very pure and graceful with this meter. If you do find one, be very gentle. They are extremely fragile. The guy who use to fix them in NY retired years ago. I think LA does still fix them when necessary.

 

Its almost like learning how fun a manual sports car can be after driving automatics your whole life.

 

Best

 

Tim

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