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Setting Exposure in the Early Days


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#1 Gary Lemson

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Posted 24 December 2009 - 08:10 PM

So...how did one set exposure in the days before light meters?
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#2 David Mullen ASC

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Posted 24 December 2009 - 08:27 PM

Before the photoelectric cell meter was invented in 1932, there were extinction meters and actinometers, but most DP's basically made a guess based on experience and Kodak's exposure guides. But remember that back in the early 1900's, pre-panchromatic film, movie film was hand-developed under a red light, so basically the negative was developed up to a desired density by eye. Karl Brown describes this in his book "Adventures with D.W. Griffith".
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#3 Saul Rodgar

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Posted 24 December 2009 - 11:03 PM

In the US, a lot of the early (mostly pre-1940) consumer 8mm and 16mm Kodak cameras had lenses with only a few apertures and the lens settings read something like this: f16- Bright Sunny Day, f5.6 - Open Shade, f2.8 -Overcast / Cloudy Day.

There were very few stocks at that time, and those cameras were designed to use only one type, also supplied by Kodak. Interior filming was not an option for most hobbyists until the GE Sun Gun (non-battery) type lights were introduced later.
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#4 K Borowski

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Posted 25 December 2009 - 12:56 AM

But remember that back in the early 1900's, pre-panchromatic film, movie film was hand-developed under a red light, so basically the negative was developed up to a desired density by eye.


This is known as "development by inspection."

Unfortunately, unless the cinematographer was developing the film he shot himself (some did) it would be difficult to communicate the level of desired density to the lab technician. There are basically two variables in addition to the chemistry.


Of course, with black and white film, there isn't the huge problem of color crossover, so there was more that could be done in terms of corrective measures in the printing of the film. But I don't think anything could be done with contrast, as still photographers could do, so this method was ultimately far more error-prone than what we have today.


Going back far enough, cinematographers used to actually frame THROUGH the film as they were shooting, without anti-halo backing or dye, and the slow film stock of the day.
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#5 Gary Lemson

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Posted 26 December 2009 - 08:53 AM

Thanks for your insights, gentlemen.

I've been watching the Scorsese documentary, "A Personal Journey...Through American Movies", which ignited my interest in the silent era, and the technology of the day.

Fascinating!
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#6 John Sprung

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Posted 26 December 2009 - 07:05 PM

A lot of the early cinematographers actually disliked the introduction of light meters. After years of learning how to judge exposure by shooting and watching dailies, they thought it was automating part of the art out of things. Early color systems required more precise exposures, so metering sort of came in along with color.

One thing to try if you're interested is to take a guess before you read your meter, and see if you can develop that long lost skill.




-- J.S.
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#7 Gary Lemson

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Posted 26 December 2009 - 11:50 PM

One thing to try if you're interested is to take a guess before you read your meter, and see if you can develop that long lost skill.
-- J.S.


Actually, I've performed some tests with 100D and K40 and no meter with moderate success. 100D tests during magic hour were the most sucessful (Well...no suprise there!). Yup...I don't think I'm ready to give up the meter, yet.
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#8 Saul Rodgar

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Posted 27 December 2009 - 12:19 AM

One thing to try if you're interested is to take a guess before you read your meter, and see if you can develop that long lost skill.


-- J.S.


I for one do try to "meter by experience" during filming. In certain situations, like when using a long macro bellows on a film camera without an internal light meter, it can be a bit of a daunting gamble --unless the bellows have a clear indication of the magnification levels -- but after lots of testing, one does really start to get a sense for exposure. Always try to double check with my meter, tho.
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#9 Brian Drysdale

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Posted 27 December 2009 - 05:03 AM

One thing to try if you're interested is to take a guess before you read your meter, and see if you can develop that long lost skill.


Seemingly Douglas Slocombe used to do this for real.

Although, perhaps if your gaffer was setting the lighting levels with a foot candle meter, you don't need to use the exposure meter.
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#10 Stephen Williams

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Posted 27 December 2009 - 05:24 AM

Seemingly Douglas Slocombe used to do this for real.


Hi Brian,

He did, I usually know what the meter will say within 1/2 stop, I generally ignore the meter or turn it until it matches what I originally thought. Agency clients get nervous if you don't use a meter.

Stephen
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#11 Brian Drysdale

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Posted 27 December 2009 - 06:00 AM

Hi Brian,

He did, I usually know what the meter will say within 1/2 stop, I generally ignore the meter or turn it until it matches what I originally thought. Agency clients get nervous if you don't use a meter.

Stephen


Yes, if you're used to using a particular range of lights you can get surprisingly close to making a good estimate on the exposure. Although, I noticed it became more difficult if you're changing video cameras all the time and there was a sudden leap in sensitivity between different models.
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#12 Tim Partridge

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Posted 27 December 2009 - 09:11 AM

From what I remember, I think in either the Christopher Challis or Jack Cardiff autobiogs either cameraman mentions how Freddie Young did it pre meters. Apparently he had an assistant who would take a tiny cut off into a dark room off set and process the frames, so Young would make trial and error judgement. To some end this kind of reminds me of what Alcott and Kubrick would apparently do years later with Polaroids. Someone please correct me if I have my facts wrong here but from memory I am pretty sure that is what one of those books said.
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#13 John Sprung

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Posted 27 December 2009 - 01:44 PM

Another story I've heard is that an early DP would look into his assistant's eyes -- to guess by the iris diameter. I kinda doubt that, as the human eye gets most of its range from changing the retina sensitivity. The actual stop range of the iris is limited, about f/2 to f/8.





-- J.S.
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#14 Keith Walters

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Posted 27 December 2009 - 07:33 PM

Another story I've heard is that an early DP would look into his assistant's eyes -- to guess by the iris diameter. I kinda doubt that, as the human eye gets most of its range from changing the retina sensitivity. The actual stop range of the iris is limited, about f/2 to f/8.
J.S.

That sounds a bit dubious, because the maximum amount the human iris opens up varies enormously with the age of the person. I've got a 17 year old niece staying with us, I'll have to get out my micrometer and measure her iris diameter in low light and in daylight. By the time you reach 60 or so your irises are almost permanently "stopped down" to about 2-3mm, which is one reason why driving at night gets more difficult as you get older.

One method of measuring light intensity before light meters was the "Grease Spot Phototometer". A spot of grease or oil is rubbed into a piece of translucent paper, the result being that the grease spot is more translucent than the surrounding paper.

If the light intensity is equal on both sides of the paper, the grease spot is invisible; if there is any imbalance, the spot appears either brighter or darker than the surrounding paper.

In a laboratory setup, the grease spot would be mounted on a slding rail so its position could be varied between a standard light source (usually a "standard candle") and the light source being measured. From the ratio of the distances from the canlde and the object, the illumination could be calculated with good accuracy.

I would imagine you could make a similar device for portable outdoor use by enclosing the standard light source in a device like an old-fashioned camera bellows. I doubt you would use a candle, more likely an incansescent lamp with a voltmeter and brightness control rheostat.

Off topic, I actually made up a grease spot photometer when I was testing compact fluorescent lamps. I was rather suspicious of the claims of lighting "equivalence" (you know: "this 10W lamp = 75W incandescent".

Interestingly none of the ISO or other standards organizations gives any requirement for verification of these figures, so I decided to run some simple tests myself.

Our test lab has a sliding rail assembly normally used for EMC compliance measurements, and I set up a grease spot sheet on top of that and taped some 240V lamp sockets on the ends.

Apart from the fact that not a single one of the dozens of samples we had bought for comparison purposes produced anything like the equivalent illumination claimed on their cartons, most of them produced less than half the claimed amount!

There were also two supermarket brands where the same pack held three lamps with different power ratings marked on them. I was a bit suspicious that, apart from the labelling, the three lamps looked identical, and sure enough, the light output was identical. They were marked as "equivalent" to 25W, 60W and 75W, but they were all closer to 20W!

The two useful things I learned are that:

You really do get what you pay for; the more expensive "name" brands do tend to actually at least approach the claimed light output, and:

The ones where the lamp is wound like a helical spring tend to have a much longer life than the more common types where the tube is made as a vertical "bundle" Don't ask me why, but it's true.
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#15 John Sprung

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Posted 28 December 2009 - 03:14 AM

The ones where the lamp is wound like a helical spring tend to have a much longer life than the more common types where the tube is made as a vertical "bundle" Don't ask me why, but it's true.


I'd guess that's more likely an indicator than a cause. Though, come to think of it, I used to have a few of the parallel type, all dead and gone now. The big factor in CFL life is how much ventillation they get in the fixture. If it retains heat, they die quicker than incandescents.





-- J.S.
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#16 Keith Walters

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Posted 28 December 2009 - 03:34 AM

I'd guess that's more likely an indicator than a cause. Though, come to think of it, I used to have a few of the parallel type, all dead and gone now. The big factor in CFL life is how much ventillation they get in the fixture. If it retains heat, they die quicker than incandescents.
-- J.S.

We had strings of 12 lights each, set up with a timer so that they ran on a 2hr 45min on/15min off cycle 24/7/365. We had 12 each of spiral and parallel types, from the same manufacturers with identical circuit boards for both types. The two types of spiral and vertical tubes were clearly from different manuacturers, so it wasn't like the explanation was simply that one manufacturer made all the spiral or all the parallel types.

We also had thermocouples taped to critical parts on the circuit boards on some of the test lamps, and although most of them got far hotter than was technically permissible, those parts weren't usually the cause of failure. The most common failure was simply one of the lamp pre-heat filaments going open-circuit.

We also had some samples of LED replacement 240V lamps, and they're simply indestructible! I guess they're simply too expensive at the moment becasue not too many people stock them. They would be ideal for places where the lamps are really hard to change.
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#17 John Sprung

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Posted 28 December 2009 - 03:47 AM

Were the test CFL's well ventilated? My experience has been that in enclosed fixtures, they die early. Yellowing of the plastic is a leading indicator that they've been run hot.

I've also tried some "40 Watt Equivalent" LED lamps, which are available here for $12 U.S. They run very cool, and seem to last quite well, though the first one, IIRC 6-8 months old, is about a stop dimmer than the most recent one. I haven't metered, but by eye, they start at about half the claimed equivalent, and the first has dropped to a quarter of it. But as nightlights on steroids, for 1.5 Watts consumed, they can't be beat. Originally, I thought to run them on timers, but noticed that the timer draws twice the power of the lamp, making it cheaper to let them run 24/7. They're also that weird pseudo-daylight color.





-- J.S.
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#18 Keith Walters

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Posted 28 December 2009 - 08:17 PM

Were the test CFL's well ventilated? My experience has been that in enclosed fixtures, they die early. Yellowing of the plastic is a leading indicator that they've been run hot.

-- J.S.

We bought some sets of the old fashioned "party lights" that consist of a string of twelve full-size different-coloured 240V 25W (or so) incandescent bulbs in conventional 240V sockets, mounted on a length of 240V cable. I presume they have/had something similar in other countries.

We mounted the strings on the ceiling of our Q.C. test warehouse, fitted them with the test lamps and basically ran them more or less in the manner they would be run in the average household. The 2 3/4 hours on - 1/4 hour off cycle is actually from a Californian standard, since at the time there was no official test standard in this country.

We enclosed some of the lamps in decorative glass covers, but it didn't seem to affect their lifespan significantly, at least for the duration of the test. The requirement is that after 10,000 hours, (a bit over a year) at least 50% should still be functioning. Few of them got past 6 months, and all the ones that almost got there were the helical tube type. I've bought nothing but "name" brands with that type of tube ever since, and I haven't had a single failure, plus the light output looks pretty convincingly like what it's supposed to be!
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#19 John Sprung

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Posted 29 December 2009 - 01:43 AM

Thanks, Keith. So the test strings were mostly in open air. Ambient temperature is also important. The worst condition is a fully enclosed decorative glass fixture in a hot room such as a kitchen. Climate also matters, here when it's hot we seem to lose more CFL's to heat.






-- J.S.
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#20 Bruce Greene

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Posted 03 January 2010 - 10:14 PM

So...how did one set exposure in the days before light meters?


Back in my AFI days, our cinematography teacher was the great George Folsey. One day he brought in his 1st light meter that he had acquired in the early 30's. I think it was made by General Electric.

George had started in silent films as an assistant and he described a technique of placing a piece of un-exposed film in the gate of the camera and covering the camera, and the head of the cameraman, with a black cloth. The cameraman rotated the iris until he could just see a certain amount of the image through the film. There was no black backing on the film in those days.

Of course, this was not the most accurate method, and the film, not being sensitive to red light was developed by inspection (I think he mentioned that one of his duties as an assistant was to develop the film). If not enough image was visible in the negative, it was placed back in the developer until it was satisfactory.
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