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Converting stills light meter to cine light meter

E

EvanProsofsky

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Hi there!

I have a film shoot coming up shortly on the SR3, but I dont have a cine light meter, I have a stills one. Difference being-I cannot adjust for frame rate with the stills meter.
Questions:
1. Would anybody be able to help me do the math to find out necessary f/stop conversions?
2. Does anybody know how reliable the internal light meter in the SR3 is?

Thanks so much,
Evan
 
Most films shot on film use an external light meters. I know that there are dedicated cine meters but for the most part, a stills meter should get you by. Funny story, There was a festival film I saw shot on 35mm using donated equipment and expired film stock. The guy did not have a light meter so he used a full frame DSLR he had and set the ISO to the speed of the stock and set the shutter speed at 1/50th (cine is at 1/48th typically for natural motion) and had the DSLR pick the aperture. Bad way of doing it I imagine but there are ways of working around the lack of a cine light meter. The great thing about film is that it is pretty forgiving.

The SR3 is a Super 16 cam I believe so the whole DSLR thing may not work and the stills light meter is probably not set for 16mm or have such a setting so you may have to get a cine light meter. However the stills meter of a DSLR could get you in the ball park.

The lack of a frame rate selector should not be an issue. Set the light meter at 1/48th of 1/50th (if that is your intended shutter speed) and set the ASA value for your film stock, the meter will tell you what stop to shoot at. Do cine meters have you input framerate? I did not know this.
 
Andrew Rieger said:
Most films shot on film use an external light meters. I know that there are dedicated cine meters but for the most part, a stills meter should get you by. Funny story, There was a festival film I saw shot on 35mm using donated equipment and expired film stock. The guy did not have a light meter so he used a full frame DSLR he had and set the ISO to the speed of the stock and set the shutter speed at 1/50th (cine is at 1/48th typically for natural motion) and had the DSLR pick the aperture. Bad way of doing it I imagine but there are ways of working around the lack of a cine light meter. The great thing about film is that it is pretty forgiving.

The SR3 is a Super 16 cam I believe so the whole DSLR thing may not work and the stills light meter is probably not set for 16mm or have such a setting so you may have to get a cine light meter. However the stills meter of a DSLR could get you in the ball park.

The lack of a frame rate selector should not be an issue. Set the light meter at 1/48th of 1/50th (if that is your intended shutter speed) and set the ASA value for your film stock, the meter will tell you what stop to shoot at. Do cine meters have you input framerate? I did not know this.
Click to expand...
Hi there,

I would assume that cine meters account for frame rate, because, as I'm sure you know, frame rate effects exposure. Eg. Shooting at 120fps takes up more light than shooting at 24. This is what is confusing me/troubling me.

Also, you say the meter is "not set" for 16mm. I do not understand. Is this to say that there is a difference between 8mm at ISOX, 16mm at ISOx, and 35mm at ISOX? Sorry, I'm confused now
 
It's simple there is no f-stop conversion. For shutter speed, use 1/50th. (it's really 1/48th but that's close enough) if you overcrank, just do the math 48 fps = 1/100th.
 
EvanProsofsky said:
Hi there,

I would assume that cine meters account for frame rate, because, as I'm sure you know, frame rate effects exposure. Eg. Shooting at 120fps takes up more light than shooting at 24. This is what is confusing me/troubling me.

Also, you say the meter is "not set" for 16mm. I do not understand. Is this to say that there is a difference between 8mm at ISOX, 16mm at ISOx, and 35mm at ISOX? Sorry, I'm confused now
Click to expand...

The frame rate is not really important as long as you know your shutter speed and film speed. As a general rule of thumb (unless you are going for a different effect), shutter speed is double the framerate. Example: 24fps uses a 1/48th or 1/50th shutter, 48fps uses a 1/96 or 1/100. 120fps would use a 1/250th shutter. Input film speed, the desired shutter speed based on your framerate and the meter should give you the stop to shoot at to get a properly exposed image.

I imagine there will be some differences between a meter set for S16 and S35 although I am not 100%. For my stills meter, there are different settings for 35mm and medium format, even though the film speed remains the same. Find out if you need a meter that does both S16 and S35.
 
There's no difference between S16 and 35mm as far as a meter is concerned. You are just determining the amount of light that is falling on your subject.
A cine meter just takes care of the calculations for you; the fps and shutter angle. However if you know the formulas then a cine meter will work just fine.
 
At 24fps the shutter speed on an SR3 is 1/48th. Set your light meter for 1/50th and it will serve you perfectly well. If I remember right, the SR3 has a variable shutter. If it does, leave it at 180 degrees. (otherwise, the exposure calculations will get really complicated.) If you overcrank or undercrank, the exposure compensation is really simple -- 48 fps is twice the frame rate, so half the shutter speed 1/96th (1/100 on a stills meter). Remember, it's just photography.
 
There is NO difference between 16mm and 35mm in the motion picture world. That has to do with the fact that we use T-stops instead of f-stops. (but that's another whole story.)
 
A cine light meter will give you results in T stops and a photo light meter will give you results in F stops (my light meter does both), but since they are so close to each other. It will not be a problem.
 
Andrew Rieger said:
A cine light meter will give you results in T stops and a photo light meter will give you results in F stops (my light meter does both), but since they are so close to each other. It will not be a problem.
Click to expand...

Sounds like FUD to me. There will be no difference in stop reading between a cine or still meter. You could simplify further, use the Sunny F16 rule & forget about meters all together.
When the ISO & your shutter speed match:-
f/16 Sunny Distinct Shaddows
f/11 Slightly Overcast Soft Shaddows Around Edges
f/8 Overcast Barely Visible Shaddows
f/5.6 Heavy Overcast No Shadows

On some older lenses the difference between F & T stops is huge.
 
Andrew Rieger said:
A cine light meter will give you results in T stops and a photo light meter will give you results in F stops (my light meter does both), but since they are so close to each other. It will not be a problem.
Click to expand...

How would the meter know what the transmission quality of the lens is? This is wrong.
A cine lens is calibrated in T-stops for accuracy, on the older lenses they had f and t-stops. Your meter will give you an f-stop, you will set the t-stop on the lens. The T-stop is calculated at the lens, not the meter.
A regular light meter will serve you fine for cinematography, a cine light meter just makes the calculations a lot easier.
 
Agreed- a meter does not care, or even know the difference between an F-Stop or a T-Stop as it cannot measure the transmission of a lens. If the F stop reading is bothering you, then just take a marker and write a "T" over the "F". ;)

Cine meters are great in that they do a lot of the math for you, and can be programed with custom settings freeing your mind to concentrate on other aspects of the production. But in the end, they are both measuring light, so you will be fine if you use a stills meter- you just have more math to do yourself. I would recommend getting the ASC Manual, as there are pages upon pages of charts and equations in there to help you figure out what exposure you need.

Another quick rule of thumb is:

ISO 100 @ 24 fps and 180 degree shutter = 100 fc at T2.8

You can then adjust from there. For example:

ISO 200 @ 24 fps and 180 degree shutter = 50 fc at T2.8
ISO 100 @ 24 fps and 360 degree shutter = 50 fc at T2.8
ISO 200 @ 24 fps and 180 degree shutter = 100 fc at T4
ISO 400 @ 24 fps and 180 degree shutter = 100 fc at T5.6
ISO 100 @ 24 fps and 90 degree shutter = 200 fc at T2.8
ISO 100 @ 48 fps and 180 degree shutter = 200 fc at T2.8
ISO 100 @ 12 fps and 180 degree shutter = 50 fc at T2.8

etc.
 
Strange, my meter gives me results in both T and F stops.
 
Stephen Williams said:
Sounds like FUD to me. There will be no difference in stop reading between a cine or still meter. You could simplify further, use the Sunny F16 rule & forget about meters all together.
When the ISO & your shutter speed match:-
f/16 Sunny Distinct Shaddows
f/11 Slightly Overcast Soft Shaddows Around Edges
f/8 Overcast Barely Visible Shaddows
f/5.6 Heavy Overcast No Shadows

On some older lenses the difference between F & T stops is huge.
Click to expand...

That rule for 24 fps 180 shutter means an ISO 50 rating.

Another way to work with a light meter and digital cameras with a wide ISO range. Pick your lens aperture and shutter speed for aesthetics, i.e. DOF control , measure incident light, find ISO for your settings and see if it falls within the camera's acceptable range. Light up or ND down as needed to compensate.
 
Ryan E. Walters said:
Agreed- a meter does not care, or even know the difference between an F-Stop or a T-Stop as it cannot measure the transmission of a lens. If the F stop reading is bothering you, then just take a marker and write a "T" over the "F". ;)
Click to expand...

Pretty much. A meter doesn't know. Most all meters will assume the F-stop represents 100% transmission at a given number because that's really all they can do without knowing specifics of a particular lens. Most of the better new/current still lenses use calculated F-stops, which are essentially t-stops, in that they are aperture settings that equate to 100% light transmission at the indicated F-number.

Where you will run into issues is using older lenses without calculated F-stops, especially lenses with many elements, longer lenses, etc.. Many of these can have an aperture of F=2.4, but a T-stop at that aperture of maybe 3.0 or more, for example. In-camera metering can help you compensate, same with exposure compensation controls. This is also why many of the better meters allow for calibration and profiling.
 
Stephen Williams said:
What is the make & model of your meter?
Is it calibrated to 12% Grey, 18% grey or something else?
http://www.bythom.com/graycards.htm
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Old Gossen from the 70's. A gift from my father. Still works like a charm. It has a cine mode which is in T stops. I have never used a modern light meter so I have no idea how they work.

EDIT: My bad, no T stops on the meter (Its a Gossen Luna Pro) It does have a cinemode which I have never used

According to the manual: "The cine scale allows direct reading of apertures for various cine speeds (frames per second). These speeds correspond to actual exposure times on the exposure time scale only for cameras having standard shutter angles. For XL cameras or those with adjustable shutter angles, consult the camera's instruction book for the equivalent shutter speeds and read your exposure opposite that speed on the time scale. Also note that some reflex viewing movie cameras use beam splitters to provide a light path to the viewing screen. These beam splitters reduce the light intensity to the film plane, so that a correction factor must be applied to the indicated f/stop. Once determined, the correction can be programmed into the exposure correction dial."
 
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The straight answer...

The straight answer...

Here's the simple answer:

1. Light meters cannot and do not know the difference between T-stops and F-stops. None of them. Still or cine.

2. At 24fps with an SR3, if you leave the shutter at its normal setting of 180 degrees, the shutter speed will always be 1/48th of a second. (If you are experienced enough to be changing the shutter angle, I don't expect that you'd be asking the questions that started this thread.)

3. If you change the frame rate, the shuter speed calculation is simple math: twice the frame rate/half the shutter speed (48fps=1/96th of a second), half the frame rate/twice the shutter speed 12 fps=1/24th of a second), etc.

4. ISO is read off the side of the film can. It is set on the light meter in exactly the same way for stills and motion. It has nothing whatever to do with fps or shutter angle.

5. The internal light meter in an SR3 is not nearly as good as a modern in-camera meter in a Nikon or Canon SLR. Also, unless you test it, it is impossible for you to know if it's out of calibration. If you use it, be very careful that you know what it is reading. A stills meter that you trust will serve you better. If you use the internal meter, take a gray card with you. Use it.

If I sound grumpy about this, I am. This was a simple question, and about half of the information in this thread is good. The other half is utter nonsense. Please stop spreading misinformation here.

If you really do not know what you're talking about, just refrain from posting.
 
All mistakes were corrected.
 
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