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Properly Exposing on 16mm Film Question


Max Thomas Schmitz

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I am shooting on film (16mm) for the first time tomorrow and need some questions answered if possible. Just for reference, I am shooting on Vision 3 500T, and on a Bolex H16 Reflex. I also rented a Sekonic L-858D-U to meter with.

 

The film is relatively simple and consists of two general locations 1) Looking out the window of a car at the stores on the street (commercial areas with more light) and 2) Inside of a liquor store.

 

Questions Regarding Metering and Exposure:

1) A question regarding the Bolex. The Bolex I believe shoots at 133 degree shutter angle and from what I have heard loses about a 1/3 of a stop of light because of the viewfinder. If I wanted to adjust that within my light meter so I don't have to always calculate, if I add a -0.33 EV adjustment in the Sekonic, is that the equivalent of accounting for the loss of a third of a stop?

 

2) Question about how to meter scene from within car looking at street. I know how the lumisphere represents a 3d object or a person and generally you point it back at the camera to find the f-stop. How do I decide generally how light or dark a landscape is for example from the camera's perspective. When I simply pointed the meter from inside the car at the street, I got a reading of f-stop 1 at 2000 ASA (2 stops over my film speed), while my lens is wide open @ 2.5 f-stop (2 and 2/3 too slow), which adds up to 4 and 2/3 underexposed when all said and done if my math makes any sense. My question being, will I get an image if in developing the image is pushed 2 stops so its only a little under 3 under. Also, to be clear, I don't need everything to be seen. It is night outside, so certain things being in shadow is fine, I just want to make sure it isn't absolutely ridiculous and that store fronts are exposed properly. I took readings from next to the store front pointing back at the street and got an f-stop that is more manageable (should I be using this reading)?

 

There isn't really a lot I can do with this one, considering I will just open all the way up and tell the lab to push 2-stops (their max), but still theoretically I would like the know if it is even worth trying.

 

3) Another question I have is when I am shooting and planning to push the film in processing. Do I need to change the ASA dial on the camera or just shoot it at 500 and tell the lab to push however many stops.

 

This has been an incredibly long and dense post, and I want to say thank you to everyone who took the time. I really appreciate it!

 

I have been having trouble trying to attach photos, particularly with the site accepting imgur links, so let me know if you would like to see photos and I can work on it.

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I assume you are talking about night shooting...

 

You could take a digital camera at the f/stop, ASA, and shutter speed you plan on shooting at to see how much exposure you'll get before the night of shooting. Incident meters don't work well in this situation, a spot meter would be more informative. 500 ASA pushed to 2000 ASA at f/2.5 means you'll probably get an image of lit store windows passing by and whatever the streetlamps are lighting. You may even get blown-out windows depending on how hot they are.

 

As for the adjustment for the shutter angle, you could just rate the 500 ASA stock at 400 ASA to compensate for a 1/3-stop loss (or 1600 ASA instead of 2000 ASA if pushing 2-stops.)

 

The lab doesn't care what settings were on your meter, all they can do is process normal, or push or pull process by your request. They don't have a way of knowing how the negative was exposed until after they develop it.

 

What does the ASA dial on the camera do anyway? Is there an internal meter in the camera? Is it just a reminder of what's inside the camera?

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Max, it's worth owning incident and spot meters so you can recc'e for shoots like this beforehand. If that rented seconic has a spot meter as well you can meter from inside the car. If there is anything in the image that has tonality about the same as 18% grey that you want to expose as normal you could use that. But I think fully open and letting some bits go hot is fine as long as it suits the style. Can you drive the route a couple of times just to meter and think about what you really want to expose...

 

In the liquour store you can meter, yes?

 

Just my 2c.

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The 1/3rd stop light loss may or may not be applicable. It will depend if you are using an original lens set supplied with the camera which has been calibrated to the camera for the numbers on the iris ring to appear "as if" there is no light loss. Lenses from other sources will be that 1/3rd stop underexposed. Better and smarter folk than I may explain this more accurately and and fewer words.

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The 1/3rd stop light loss may or may not be applicable. It will depend if you are using an original lens set supplied with the camera which has been calibrated to the camera for the numbers on the iris ring to appear "as if" there is no light loss. Lenses from other sources will be that 1/3rd stop underexposed. Better and smarter folk than I may explain this more accurately and and fewer words.

 

No Robert! No lenses have their aperture marks adjusted for the prism light loss in a Bolex! A lens marked RX is only optically adjusted to compensate for the abberations introduced by the prism, not the light loss. The f stops are like those on any other lens, and relate to the lens only. Sorry to be abrupt, but this is a misconception I see repeated all the time, which only adds to the confusion about Bolexes.

 

If you think about it, it would be crazy for RX lenses to compensate for the Bolex prism light loss, when lenses over 50mm were not made in RX variants. The abberations introduced by the prism are minimal at those focal lengths (hence no RX versions), but the light loss is the same! So you'd have to constantly adjust your exposure reading, alternately compensating then not compensating, when swapping from say a 75mm to a 25mm, which would be nuts.

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Questions Regarding Metering and Exposure:

1) A question regarding the Bolex. The Bolex I believe shoots at 133 degree shutter angle and from what I have heard loses about a 1/3 of a stop of light because of the viewfinder. If I wanted to adjust that within my light meter so I don't have to always calculate, if I add a -0.33 EV adjustment in the Sekonic, is that the equivalent of accounting for the loss of a third of a stop?

 

 

There are a number of threads about this question, recently this one popped up again:

http://www.cinematography.com/index.php?showtopic=46459

 

Richard Tuoey's answer in post #12 answers it pretty succinctly. If you use a meter in cine mode, which assumes a 180 deg shutter, then you need to adjust 1/3 stop for the 133 deg shutter of the Bolex, and another 1/3 stop for the prism light loss. The easiest way to meter that is to adjust the ASA on the meter by 2/3 stop slower, so for 500 ASA film, rate it at 320 ASA.

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The lab doesn't care what settings were on your meter, all they can do is process normal, or push or pull process by your request. They don't have a way of knowing how the negative was exposed until after they develop it.

 

If you have a nice Lab, you could shot the scene for like 10' feet, cut the film and put it on a smal spool, before shoot regulary. Then ask to develop the teststrip first to see if a push / pull is needed. My lab does that for additional cost. However, i would only do it if necessary.

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  • 4 years later...
On 2/7/2019 at 1:42 PM, Dom Jaeger said:

 

There are a number of threads about this question, recently this one popped up again:

http://www.cinematography.com/index.php?showtopic=46459

 

Richard Tuoey's answer in post #12 answers it pretty succinctly. If you use a meter in cine mode, which assumes a 180 deg shutter, then you need to adjust 1/3 stop for the 133 deg shutter of the Bolex, and another 1/3 stop for the prism light loss. The easiest way to meter that is to adjust the ASA on the meter by 2/3 stop slower, so for 500 ASA film, rate it at 320 ASA.

Sorry to dredge this up - but  I was reading on http://bolexh16user.net/ExposureAdvice.htm that the Bolex does NOT have 133 degree shutter, but it is 130 degree. Which is correct?

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Hello Bruce,
a full circle is 360°. Hence, 1% of a circle is 3.6°. In other words: the difference between 130° and 133° is less than 1%. Nobody cares about this small difference when it comes to measuring the exposure. When you’re shaking a handheld exposure meter a little bit, then you’ll cause a greater difference. 

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16 hours ago, Bruce Herbert said:

Sorry to dredge this up - but  I was reading on http://bolexh16user.net/ExposureAdvice.htm that the Bolex does NOT have 133 degree shutter, but it is 130 degree. Which is correct?

There is some good information on that site, but also some misinformation, typos, and misunderstandings like this one. I tend not to recommend it as a reliable source of info. 

A lot of Bolex literature simplified things like exposure times in order to have nice round numbers. The early Bolexes had a shutter angle of around 172 degrees, but at 16fps this works out to be 1/33 second exposure time. To make things simple, the Bolex manual just rounded it down to 1/30 second, which is why some reference guides reverse calculated a shutter angle of 190 degrees.

In the same way, the actual shutter angle of a H16 reflex Bolex is around 130 degrees, which works out to be a tad over 1/66 second at 24fps, but to simplify things the manual rounded off the exposure time to 1/65 second (or 1/80 adapted for the prism loss). When you calculate the shutter angle for 1/65 it turns into 133 degrees, hence the confusion.

But as Joerg said, the difference is negligible in terms of actual exposure. Even the difference between 172 and 190 degrees, which seems a lot, works out to be about a fifth of a stop. The overexposure actually probably helps account for the internal light loss of the lens, which can be at least that much. 

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