Dark Side Of The Light Meter

Hello everybody,

I recently joined this forum and I've been learning a lot since then. As a token of my gratitude I'm here to share some of my confusion for the first time. Please go easy on me...

Few weeks ago I decided that it was about time to start saving on ice cream and to spend some money on one or two good light meters. During my investigation I've noticed that the specs of all the meters that I've been able to look at, lack a very important piece of information, that is their spectral response. I've written to Minolta, Sekonic and Gossen asking for their meters' SR but I didn't get any answer. The only information about the SR of a meter I've been able to find is for the Zone VI modified Pentax Digital Spot Meter that is calibrated to be used with Kodak Tri-X B&W still photography film, and that film's spectral sensitivity chart can be easily found on the Kodak website.

All this led me to think that, if the manufacturers don't provide any SR for their meters, it's probably because they're flat, so when I use an incident meter I shouldn't worry too much about its SR and when I use a spot meter I just have to compensate by eye for the SS of the film stock I'm using. To confirm my hypothesis I tested a couple of meters that I could get my hands on by taking B&W stills of plates of different very saturated colors. My empirical observations led me to realize that the spectral response of those meters is far from being flat, with some giving ridiculous readings toward the blue end of the visible spectrum. My means (not to talk about my knowledge) were too rudimentary to get any further than this simple conclusion.

Just not to seem too foolish, before writing this email I tried to find an answer to my questions on several books like the ACM, both Blain Brown's books and several others but I haven't been lucky. The only book where I've found some, but not much, useful information on the subject is Ansel Adams' The Negative.

Even if not directly related to the meters' SR, a disconcerting discovery I made on Ansel Adams' book is that even if the light meters manufacturers tell you their meters are calibrated to 18% grey they are not. Apparently almost all meters include a 'K-factor' that makes them read to a grey that is usually between 10% and 18%. If I'm not mistaken, only Sekonic acknowledges this in its meters specs. Anyway, at least once you know this fact, it's easy to compensate...

In conclusion, all I can say is that I'm confused and at the same time I'm sure I'm overlooking something. Is there someone kind enough out there that can shed some light on the subject?

Thanks

Simone "I just wanted to buy a meter or two" Rapisarda
Montreal, Canada

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Hello -

I actually just bought another meter today. My nice little studio deluxe II just didn’t cut it for some of the low light photography/cinematography I’ve been finding myself doing. My take on this situation is that I don’t think it really maters what meter you get. They all work quite nicely.

I picked up a used Spectra IV-A for a couple of simple reasons. It fits nicely in my hand, it doesn’t have many moving parts to accidentally bump or press like those damn Sekonic “do it all” meters, it’s simple to use, it’s easy to read, it cost $200.00, and last but most important – I just like it better then other incident meters for some other unknown reason.

I’ve see pictures of Storaro using a studio deluxe II, Nykvist with a Pentax digital spot meter (zone VI maybe?), Almendros with a Luna Pro, Conrad Hall and Michel Chapman with the old Spectra Pro, and most of the DP´s I work for with those darn “do it alls” that I dislike so much. So my advice is to buy the meter that fits your personality and metering style. I’m still bent on buying a Pentax digital spot since I’ve raised myself analog spot metering through my old manual SLR over the past 7 or 8 years.

Using incident meters just doesn’t feel the same (but I just bought that Spectra! What was I thinking?...I was thinking that I don’t have $500+ to blow on a Zone VI meter at this moment in time).

I’m sorry if none of this helped you in any way, but it’s my take on the “what meter should I buy” issue.

Good luck,

Joe Zovko
AC
LA, CA

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>if the manufacturers don't provide any SR for their meters, it's probably >because they're flat, so when I use an incident meter I shouldn't worry >too much about its SR

They are far from flat, although they don't seem to be as bad as they used to be. Mark Woods is probably the person to ask about this; perhaps we'll hear from him.

The very general rule of thumb I've always used is that at the extreme ends of the spectrum (very red or very blue) meters tend to be less reliable and it's time to go to a Polaroid. I wonder if others take a similar approach.

Certainly, if you find this information, please share it with everyone.

Search the CML website, it might already be there.

>Even if not directly related to the meters' SR, a disconcerting discovery I >made on Ansel Adams' book is that even if the light meters >manufacturers tell you their meters are calibrated to 18% grey they are >not.

Also, as you know from Adams, ultimately, the final calibration is by you using the film stocks and conditions under which you normally operate. This is probably why most DP´s don't worry too much about exact spectral response charts or sensitivity curves published for film stocks : except in a very general way. It's the actual use that counts.

Testing is everything.

You can obtain most Kodak or Fuji film stocks in still camera cassettes, test them and have them developed as slides or prints. This is probably the best way to test them if you don't have ready access to a camera. Be rigorous in your testing and it will reveal just about everything you need to know about the meter and perhaps more importantly your metering technique. (If you can't find them in Montreal, they can be obtained from RGB Labs in Hollywood. They also do the processing.)

In your case, pay particular attention to extremes of lighting conditions : reds at one end and blue/violet at the other; also sodium-vapour, mercury vapour, other sources that are not full spectrum, etc. Include a grey scale and, if you can, a Macbeth color chart in each scene you shoot (very important in the extreme color conditions to understand not only how the meter responds but how the film responds).

If you can, also take a Polaroid and include notes on the incident reading, where you set the stop and perhaps most important : reflectance/spot readings of the shadows and highlights. This is a film education in itself.

Processing them as slides is the most important, but the prints can be useful for other purposes. Be sure to examine the original negative as well. Mark Woods does his analysis on a densitometer; perhaps your local lab can help you with that. For extreme color conditions and evaluating the meter's response, this would be very useful. Learning to recognize a solid negative by eye is a valuable skill in any case. Be sure to shoot some over and under exposures for comparison.

Do the tests carefully and share the results and you will earn the gratitude of your fellow cinematographers. Finding charts from the manufacturers is not likely to be easy; I've tried. Even if I had these charts, I'm not sure I would have included them in the books except as a rough starting point: ultimately it is the testing by each individual that is the ultimate calibration. Look at Mark's website for the excellent work he did with film response at sunset — extremely valuable research. I think there is a link at CML.

Very commendable that you did the tests with the color plates. I think you will find that B&W film is more sensitive to extreme color conditions than is color film, particularly at the upper end. One of the most intriguing aspects of the Zone Six calibrated meter is the ultraviolet filter : very useful at high altitude. Keep in mind, however, that meter is specifically designed for black-and-white zone system work.

For color negative work in film, quite frankly, the techniques are not nearly so exacting. Usually, in film, it's more about controlling the lighting than about controlling the negative in the darkroom. (Certainly, I am in NO way implying that careful metering is not important, in fact, I'm a bit of a nut about it myself. I come from a Zone System background myself.)

Good luck

Blain
DP
LA

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>The very general rule of thumb I've always used is that at the extreme >ends of the spectrum (very red or very blue) meters tend to be less >reliable and it's time to go to a Polaroid. I wonder if others take a similar >approach.

Who's to say (without extensive testing) that Polaroid B&W film had the spectral response that matches the color film we use today. Metering for exposure is a subject and interpretive art. Since I only use Minolta Digital Spot Meters and the Last Gray Card (yes, I calibrate to it. So who cares what percentage reflectance it is, just so it is consistent) I have found that the few anomalies that I see are not enough to offset exposure a whole heck of a lot. If I'm doing something wildly to either end of the spectrum I test it. And If I can't I allow an intuitive overexposure for deep reds and deep greens.

Minolta has always been very responsive to my technical questions (even when I was just getting started). After the (American holiday) weekend I will call them and try to report an individual that you can contact for information. They even sent me a chart that showed the offset for primary red light. Also, I always found the old mechanical meters completely unreliable. Depending on how you held them you could get widely varying readings because of the weight and balance of the needle. And if you breathed on them funny they would go out of calibration. Very touchy.

I think the onset of digital metering (no matter what the spectral response) was a boon to the photographic process. Remember, when you were working with ASA 25 film you could be off 100 or so foot candles and still get decent exposure. But with 500 ASA just a few foot candles can mean a significant exposure difference.

Steven Poster ASC

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Steven Poster ASC wrote :

>I think the onset of digital metering (no matter what the spectral >response) was a boon to the photographic process. Remember, when >you were working with ASA 25 film you could be off 100 or so foot >candles and still get decent exposure.

I wonder if anyone still remembers the extinguishing type meter. I inherited one from Roy Tash csc (died 1988 I think, well-known cameraman) who used one since he started in the News Camera business back in 1916. Roy never used anything else, yet his exposure was always dead on-he was known for it.

This one has 1922 engraved on it. In short, you compared the light with a corresponding filter. I think it was called E.I. then, exposure index and it was calibrated to ASA 16, or the equivalent of whatever the E.I said. I used it on several occasions and found it highly accurate, at least with Gevaert reversal stock. Never pursued it however, naturally I would not want to be found dead using it, I had a Spectra. True enough, the Spectra was often inaccurate in case you held it on its side, especially at 40 below in Edmonton and points north. Then I used the extinguishing meter, was always dead on in snow conditions, specially on slow speed stock...

Robert Rouveroy csc
The Hague, Holland

I plan to live forever. So far, so good.

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>Who's to say (without extensive testing) that Polaroid B&W film had the >spectral response that matches the color film we use today.

For situations like that I generally use color Polaroid (for normal scenes I use the high speed black and white). I tend not to use Polaroid nearly as much as I used to, except for green screen work.

Your statement is certainly correct but I'd have to say that I have tested it, not to a level of scientific accuracy, but enough to satisfy me that it works for my use. I certainly concur that the old mechanical meters were much further off. I've been aware of it since my Photography 101 teacher many years ago told a story about shooting Peggy Lee in a nightclub under red spotlights and getting burned on the exposure.

When I'm in doubt about a heavily coloured scene, I used to read with the Minolta digital, the old Spectra mechanical meter and also with the Pentax spot meter with a grey card (and have the gaffer read with his meter also) - none of them agree, of course. (I rarely use the old Spectra anymore; as you say, it is not very reliable or accurate, certainly not for this kind of situation.)

The differences in the readings for the three meters are quite interesting: and unnerving (especially early in your career). Consistently, I've found that the Polaroid is the most accurate and generally agrees more closely with the digital meter than the mechanical — but not completely. Can't claim scientific accuracy but for my own use it seems to work pretty well; to date I've never had an exposure problem with heavily coloured scenes; except once.

It was a scene in a Chinese restaurant: a meeting of the Chinatown elders. In rehearsal I noticed that the large neon sign in the window spread this wonderful deep orange glow over their faces (they were at a table by the window).

Beautiful, moody, mysterious light but at the bottom end of exposure (way off the bottom end according to the Spectra, closer but not quite on the Minolta and Pentax). I got the gaffer started on building a rig that would duplicate the look as closely as we could.

Then I decided to be a bit bold and I took a Polaroid. I told the gaffer to stop (we were also running out of time on the permit and the SAG actors were perilously close to overtime). The Polaroid told me I could do it when the meters said "don't be ridiculous."

A while later there were shake-ups (director fired in post, that sort of thing) and I got a call from the producer "We're having trouble with the scene, the lab thinks it's underexposed." This is the call that every DP dreads.

He told me "We had a hell of time getting all the orange out of it and when they did, it's all grainy and underexposed." I explained (as calmly as I could) that there was nothing BUT orange in the scene and if you take it all out, there is very little image left at all. They reprinted and it worked fine; still my favourite shot in the movie.

So bottom line in this situation: couldn't trust the meters in this case. The Polaroid, if nothing else, emboldened me to "go for it." What appeared to the producer to be an exposure problem turned out not to be.

That's really the story with meters, Polaroids, grey cards, etc: every DP uses them in their own way - factoring in their own experience and calibration adjustments.

It really gets back to the "personal calibration" that is at the heart of the Zone System. Back when I was a gaffer I saw DP´s use meters in some pretty idiosyncratic ways: it sometimes seemed that the more famous the cameraman, the more unusual his metering method; but obviously it worked for them.

Blain Brown
DP
LA

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> I wonder if anyone still remembers the extinguishing type meter.

I was given an Extinguishing Meter by my mentor, Ralph Woolsey, ASC. It is a Bell & Howell manufacture, but I've never been able to find any information on operating it. Its been languishing in my Closet of Strange Film Chunks the past 15 years or more -- can't bring myself to throw it away, though.

Gerry Williams
Director of Photography
San Diego, CA

"Living on Earth is expensive, but it includes a free trip around the sun."

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Blain Brown wrote :

>The very general rule of thumb I've always used is that at the extreme >ends of the spectrum (very red or very blue) meters tend to be less >reliable and it's time to go to a Polaroid. I wonder if others take a similar >approach.

Definitely, I've found ALL meters to be unreliable with both Green & Blue screens and with measuring TV or computer screens.

Video assist, a good one, can be very useful with the extremes as well. I always use the VA for balancing TV screens that are in set.

And by ALL meters, well I'm a bit of a meter freak. I've got Spectra's, Minolta's, Sekonics, Gossens, Pentax and err.....

I use the Pentax digital spot for most screen work as it seems to be the least sensitive to extreme colour but always use the Polaroid 600SE when in doubt!

I'm currently using the Minolta 6 as my standard meter, a lovely toy.

Cheers

Geoff Boyle FBKS
Director of Photography
EU Based
www.cinematography.net

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Robert Rouveroy csc writes :

> I wonder if anyone still remembers the extinguishing type meter.

I have one that I bought in a "antique's" shop on the quayside in Exeter, it cost me a whole $4

Cheers

Geoff Boyle FBKS
Director of Photography
EU Based

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Geoff Boyle writes :

>Definitely, I've found ALL meters to be unreliable with both Green & >Blue screens and with measuring TV or computer screens.

>And by ALL meters, well I'm a bit of a meter freak. I've got Spectra's, >Minolta's, Sekonics, Gossens, Pentax and err...

Have you tried that marvel of British engineering known as the SEI (Salford Electrical Instruments). For the uninitiated, it is a 1/2 degree spot meter that uses the extinguishing method, except that it contains its own comparison lamp and calibration circuit.

It is extremely accurate and since it does not use a photo cell, it is immune to extremes of color.

The drawbacks are that the image is inverted and it is not easy to use and in their day, they were very expensive. I don't think Salford is still around, but the meters do crop up at used equipment shows from time to time.

No collection is complete without one.

Brian Heller
IA 600 DP

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Brian Heller wrote :

>Have you tried that marvel of British engineering known as the SEI >(Salford Electrical Instruments). For the uninitiated, it is a 1/2 degree >spot meter that uses the extinguishing method, except that it contains its >own comparison lamp and calibration circuit

We got one in 1956 and I used it for about 35 or 40 years, mainly in photographing old masters. The painters painted very deep, tonally, and a "pure white" in the painting would be somewhere in the vicinity of perhaps 25% reflectance. SEI had the only spot meter out there in those pre-CdS meter days, so it was the only game in town. Very reliable once you learned how to match the illuminated spot to tones that were not necessarily neutral.

Unfortunately, a "leak proof" Eveready cell leaked into it and ruined the meter. Fortunately, Eveready was as good as their word and replaced it with a Zone VI Pentax at our request, the SEI being long out of manufacture. Frankly, I prefer the Zone VI (it's an analog model) to our Pentax digital. I just prefer seeing the needle indicating a very specific reading, instead of the digital's f/number plus or minus 1/3 stop LEDs. The digital is more compact and you can see the readout when reading in very dim light, but it doesn't like chopped light, like regular fluorescents. You can read subjects illuminated by fluorescents, but when you try to read the tubes themselves the reading oscillates. OTOH, the analog’s scale disappears when you try to read a spotlighted subject with a dark surround. The scale in the dark. And there is no way to tell if the needle zeroes when there is no light. With both meters the spot itself is very hard to find when trying to read very dark subjects. I have to move the meter around trying to locate the spot, then guide it to the subject. The digital meter is more than 10 years old, so maybe that aspect has been improved.

Wade K. Ramsey, DP
Dept. of Cinema & Video Production
Bob Jones University
Greenville, SC 29614

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> extinguishing type meter

I've heard of these but never seen one. How do they work?

Blain Brown
DP
LA

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Blain asked:

> extinguishing type meter

>I've heard of these but never seen one. How do they work?

They consisted of a viewing port or ports through which the scene could be viewed through a progressive series of ND filters. You ran through the ND filters until you came to one that just extinguished the view and that gave you a reference number to dial in for your exposure. Sort of a calibrated contrast viewing filter. And like the viewing filter, your eyes had to be adapted to the scene's light level and you couldn't view through it long enough to allow your eyes to accommodate to it.


Wade K. Ramsey, DP
Dept. of Cinema & Video Production
Bob Jones University
Greenville, SC 29614

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Brian Heller wrote :

> No collection is complete without one

I used to have one, but sadly let it slip from my fingers...

Jeff "only has a minor collection of light meters" Kreines

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