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How do i use an external lightmeter


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#1 Bjarne Eldhuset

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Posted 07 August 2006 - 01:34 PM

Hi, I'm (still) a newcomer to super 8, and I guess I could just as well have called this thread "the idiot's questions about light measuring", as I probably will be asking some very basic questions here.

I've previously shot on video, set the white balance, and just had the camera make all (not artistical:-) decisions for me. I've just purchased two super 8-cameras, and next weekend i intend to shoot 2-3 test rolls of Vision 2 200t and Vision 2 500t. Now, for the questions:

1. I've read that these films will give the best results if shot at f-stops between 5.8 and 16. Anyone now if this is correct? At which f-stop will the picture have least grain? How much light is enough light, and how little is to little to capture motion acceptably?

2. I tried placing my brother on a chair sitting next to a window. When using a minolta autometer IV-f, the window was approximately f-8, whilst in front of my brother, approximately f-2.

At which f-stop should I shoot to get my brother to be most visible?
At which f-stop should I shoot to get the window not to blow out?

3. Say I have a 5 meter wide white wall in a room. In the right corner a man walks around in circles. In the left corner sits a woman in a chair, next to a roof-light.
Say the meter reads f-2 for the man and f-5.6 for the woman.
- If i shoot at F-2, will the woman be overexposed, or will nothing in the range from x stop to z stop be overexposed?
- If i shoot at f-5.6, will the man be very dark?

I i had shot the same scene with the meter reading f-5.6 for the man, and 11 for the woman, would the man be as light as the woman was in the previous shot, and the woman much lighter? How do I use my light meter to find out wether or not a shot will be too dark or too bright?

Lots of basic questions here, and I don't expect you to answer, but I will surely be grateful if you do!

Best regards from Bjarne in Oslo.
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#2 Andy_Alderslade

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Posted 07 August 2006 - 03:28 PM

Firstly you say you just bought two new cameras - its best you test your super 8 cameras with some reversal film, why? Because super 8 cameras are old and go wrong, and you can easily project reversal film and see how well the cameras work. If you shoot negative like the Vision 200 T you have to telecine them, which makes things very expensive.

1. The statement you read is slightly inaccurate, though wide-open f-stop (1.4,2,2.8) may very slightly increase grain, it won't nearly as much as using higher films speed, or push processing or underexposing and correcting in post certainly will. Practicly speaking you should take advantage of shooting wide open if it gets you an acceptable exposure, or even allowing you to over-expose it by 1/3 to 1 stop over to minimize grain. Some people in this forum are advocates of shooting middle of the scale because it hides the lack of sharpness possessed by some super8 camera lenses - but some lenses are perfectly exceptable for such a grainy format, so you may want to test that. Personaly I like shooting wide open as it restricts what would be a very deep depth of field.

2-3 This is where its important to know if you are using your lightmeter properly - and I hate to admit it the first time I shot super 8 with an external light meter I had it pointed the wrong way!

You should place the sphere of your light meter right up to your subject with the sphere facing into the direction of the camera lens - without casting your own shadow over it. The sphere is averaging out the light which is bouncing off your subject into the camera lens.

Essentialy that means if you want your brother to be exposed correctly take the light reading at his face under the same shadows he is under, if you want the window correctly exposed (which means your brother will be silhoetted) take the light reading outside or if not possible with the sphere pointing out the window. If you want both to be correctly exposed you will have to provide more light on your brother so they are within an acceptable range of each other, maybe 1, 2 or even 3 stops difference will be acceptable but it depends on your taste of what you think is a natural range. The advantage of film is that letting windows burn out looks more natural than in video. If detail on both are important maybe you should try and keep them within a stop of each other, but its worth testing your tastes.

If in doubt its best to have your most important subject at the correct exposure indicated by your light meter, unless there is a dramatic reason otherwise.

The lightmeter is essentially giving you the optimum exposure for the area where it physically is, so it comes down to your decisions of letting areas of the frame under or over expose. If all the lighting is flat across the field in view and you expose exactly as the lightmeter tells you, the whole image will be at the correct exposure. If you have areas of light and dark, how light and dark they come out as will depend on where you took your reading, ie if you take your light reading at the dark areas, they won't come out as dark but as averagly light.

You should definatly test this all out with some reversal film and project it at home and see what you like and can get away with. Plus reversal is slightly higher in contrast, so if you can get it right in reversal, you can get it right on Negative stocks.

Now stop asking questions and go shoot some film dammit!
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#3 Matt Pacini

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Posted 07 August 2006 - 03:39 PM

Almost all Super 8 cameras use beam-splitters, which steal light from your exposure.
So, while you would think that you would get a more accurate exposure using a light meter, with S8, the opposite is true, unless you can calculate EXACTLY how much light your beam-splitter is stealing.

If the internal meter is functioning, us it instead for Super 8, otherwise you're going to end up with underexposed film.
I learned this the hard way long ago.

MP
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#4 Andy_Alderslade

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Posted 07 August 2006 - 03:49 PM

Almost all Super 8 cameras use beam-splitters, which steal light from your exposure.
So, while you would think that you would get a more accurate exposure using a light meter, with S8, the opposite is true, unless you can calculate EXACTLY how much light your beam-splitter is stealing.

If the internal meter is functioning, us it instead for Super 8, otherwise you're going to end up with underexposed film.


Well unless the camera's manual doesn't tell you the variation, wouldn't it be more practical to make the effort to compare the reading of the internal (aimed at a greyscale) with the reading of an incident meter, and note the difference?
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#5 Chris Gravat

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Posted 07 August 2006 - 05:40 PM

Well unless the camera's manual doesn't tell you the variation, wouldn't it be more practical to make the effort to compare the reading of the internal (aimed at a greyscale) with the reading of an incident meter, and note the difference?


I am going to have to agree with Andy. Plus you will be much happier with the results you get with an incident meter because of how precise you can get. I recommend the book "Motion Picture and Video Lighting" By: Blain Brown to get you started. It will give you a basic understanding of lighting for film.
Good luck.

- Chris Gravat
Orlando, FL
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#6 Anthony Schilling

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Posted 07 August 2006 - 06:11 PM

I have to agree with Matt- My S8 internal meters have always given me accutate results, more so than with an external meter... so why overcomplicate things. Still not a bad idea to figure out the spitter reduction, an external meter can still come in handy at times.
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#7 Chris Gravat

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Posted 07 August 2006 - 11:09 PM

I can see how you guys can like the internal spot meter, I mean it's quick, it's easy, It's built in. What's not to like? But when it comes down to it if you want to know how everything is going to expose precisely, am i within my lattitude?, yada, yada, yada. Then use an incedent meter.

As stated before briefly, the incedent meter gives you a reading based on acual light falling on the subject. The spot meter in your camera is metering the light that is bouncing off of your subject (reflective), which can add quite a large margin for error.

I know I will continue to use my sekonic meter when shooting super 8 and any other format.

- Chris Gravat
Orlando, FL
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#8 Anthony Schilling

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Posted 07 August 2006 - 11:56 PM

I use a sekonic sometimes, but more so indoor lighting situations... but the internal meter can be used very easily and effective to meter areas of a scene and lock your exposure for what you want to hit.
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#9 Andy_Alderslade

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Posted 08 August 2006 - 07:11 AM

I use a sekonic sometimes, but more so indoor lighting situations... but the internal meter can be used very easily and effective to meter areas of a scene and lock your exposure for what you want to hit.


Its too easy for a bright practical or a bright background to cause the subject matter to be underexposed when using the internal meter. This is particularly bad with the negatives stocks, because the colourist in telecine will probably try and fix this making the subject matter excessively grainy.

Remember that many internal meters take an average from the whole frame, they're not like the spot meter found in new SLRs.

When I got a Nizio Proffesional 2 years back i shot serveral rolls of K40 using the internal meter (including the automatic time lapse) and all were about 2/3 under exposed. When I went out and shot with an incident meter I completly forgot about the issue of lost light to the viewfinder (i'd been using a Beaulieu for the last year or so - which doesn't have the issue) but despite this all the exposures were far better than on the previous rolls. I guess the lesson was, even a slighty underexposed incident reading will be more reliable than that from a camera's light meter which is over 30 years old.

Remember that many proffesional super 16 cameras do have internal light meters, Aaton XTRs, Arri SRII (can't remember if the SRIII does) but you won't ever find a proffesional DP relying on one, if they use it at all.
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#10 Bjarne Eldhuset

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Posted 08 August 2006 - 08:35 AM

Hi again, and thanks for all the good advice. I haven't been able to answer before now, due to a messed up internet-connection.

I will be testing both the internal and the external light meter, and make notes, so i hope to get a good idea about the difference between the internal and the external light meter.

Andy:
- I will be testing with some rolls of negative stock, since my first real project on super 8 will be shot on negative stock as well. A bit expensive, but I need the experience with this stock. And anyway, who needs money, a happy girlfriend, and the ability to have a social life, when one can spend all time and income on super 8!

- Thanks for the practical advice on how to use the light meter. Guess you saved me from measuring myself instead of the subject :-)

Then, a question about distance:

A. INTERNAL LIGHT METER: Since the internal lightmeter is metering the light that is bouncing off of your subject, I guess it would make quite a difference how far your camera is from the subject you're filming? Standing 5 meters from a person should possibly give quite a different reading from the internal light meter than standing, say, 25 meters from the subject?

B. EXTERNAL LIGHT METER: A person is standing on point X. Using the external light meter, you get a reading at point x. You then do 3 shots, one at 5 meters away from X, one at 15 meters away, and one at 30 meters away. Will the exposure be the same for these 3 shots? Does the camera's distance from the measured object matter?

Thanks again for all your answers and good advice, they have really helped me! Bjarne, Oslo, Norway.
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#11 Andy_Alderslade

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Posted 08 August 2006 - 09:16 AM

A. INTERNAL LIGHT METER: Since the internal lightmeter is metering the light that is bouncing off of your subject, I guess it would make quite a difference how far your camera is from the subject you're filming? Standing 5 meters from a person should possibly give quite a different reading from the internal light meter than standing, say, 25 meters from the subject?

B. EXTERNAL LIGHT METER: A person is standing on point X. Using the external light meter, you get a reading at point x. You then do 3 shots, one at 5 meters away from X, one at 15 meters away, and one at 30 meters away. Will the exposure be the same for these 3 shots? Does the camera's distance from the measured object matter?

Thanks again for all your answers and good advice, they have really helped me! Bjarne, Oslo, Norway.


Distance from subject to camera doesn't really affect the light needed for exposure, only how close the actual lights are to a subject will affect the light levels.

Though its worth noting the internal light meter will be tricked by the colour of objects, for example if a large white wall features in a large part of the frame, the internal meter will try to underexpose from the correct amount. If a dark blue wall features heavily it will try to over-expose from the correct level. The incident meter will always give you the correct level providing it is in the point in space you want exposed correctly and that you have the sphere facing the camera lens.

Always take an incident light reading immeadiatly before each and every shot right up to the subject featured - this will ensure not being tricked by clouds or the actor drifting slightly into shade.

As noted here use your tests to find out the light lost to the viewfinder, so you can compensate during shooting. It will probably work out to be around 1/3 stop.
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#12 steve hyde

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Posted 08 August 2006 - 10:32 AM

...Light meters are always an approximation regardless of whether we use an internal, external or just use our eyeballs. I suggest taking Andy's advice to shoot some film and find out what happens. Learning to use an external hand-held device is an important aspect of cinematography as is being able to choose an F-stop without metering at all.... I think the rule of thumb here is to choose a metering method and then consistantly use that method for consistant results. I think Matt's warning about beam-spliting meters and variances among metering techniques is important to keep in mind, but it is not a good reason to trust the internal meter more than an external one. If you plan to shoot 16mm and larger gauges, I suggest learning to use a hand-held meter.

Steve
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