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Shedding Light on Light Meters

Posted on September 02 2018

For our next article in the series with Howard from Devizes Darkroom we ask him to explain how to use analogue light meters - and why you would need one if your camera has an inbuilt sensor. Howard, over to you...

Exposure Meters and how to use them

photo of light meters

With the resurgence of interest in film photography, people are now discovering that taking manual control of the camera exposure settings is an enjoyable part of the process.  Even if you have bought a super-expensive point and shoot with fully automatic exposure, you still might pick up something useful, so read on.

Latitude, Schmatitude.

Isn’t Sunny 16* good enough?  It is true that Sunny 16 (see below) works for most outdoor photography, it relies on the built-in tolerance that modern films have. A medium speed black and white film will have a tolerance range (often called “Latitude”) of exposure error of up to 5 f stops, if the lighting is even.  A colour negative film like Portra will forgive errors of up to 3 stops and a colour reversal film like Ektachrome will tolerate very little error, about half stop over and one stop under.

What that means is that if the correct exposure is f8 at 125th of a second, a b/w film will still give a usable result if underexposed at f16 (two stops under) or F2.8 (three stops overexposed).

bracketed film - 35mm

Strip of negs bracketed: “one on the meter, one above and one under”

 

What difference does it make?

Using the example of colour film, an under exposed negative will have muted colours, milky shadows with no detail and show more grain that expected. An over exposed negative will have vivid colours, but the brightest parts of the picture, like faces, will have “crushed” tones, often looking just solid white or yellowish and lacking detail.  Colour transparency film goes from nearly black at 3 stops under to very pale and lacking detail at two stops over or more.

In the golden age of “holiday snaps” both Kodak and Ilford spent a huge amount of R&D on concocting the perfect “amateur” black and white film. A chemical wonder with several layers of emulsion on top of each other with different sensitivities, so you really had to mess up badly not to get a reasonable “snap” (Kodak “Verichrome” and Ilford “Selochrome” are examples) Only professional photographers used exposure meters in those days, their cameras had shutter speeds and f-stops to adjust, the normal family camera might have “Bright Sun or “Cloudy” settings, if any at all.

Black and white film is more tolerant of exposure errors it is true, but if you want to get the very best result out of that expensive roll of film you just loaded, accurate exposure (and development) will give you the longest tone range available on the negative.  Medium speed B/W film can show a usable range of tones covering about 7 stops. Please don’t jump down my throat for saying that, I am sure that the techies out there will know that is a simplification, but most b/w printing papers will struggle to reproduce anything more than that.  If you only look at your pictures on a tablet or phone, you may see a bit more.

So, exposure meters are a big help in getting the best out of your film.  Don’t be put off by the apparent complexity of the settings dial, it is not hard to understand at all.  True, a 1970’s German meter like the Gossen Lunasix looks like something from NASA, but that is just an example of Teutonic thoroughness.

close up of lunasix light meter

Lunasix dial close up “not really that complicated”

How to use a meter

Whatever meter you choose, the operation is largely the same, you point the meter at the thing you want to take a picture of, press the button to take a reading and then read off the dial the appropriate combinations of f-stops and shutter speeds.  F-stops give evenly spaced changes in exposure of one F-stop, Shutter speeds do the same, so as you go up on the f-stop scale (from f8 to f11, for example) you change the shutter speed to compensate for the change (250th of a second down to 125th of a second). In each of the cases, (250th at f8 or 125th at f11) the exposure is the same amount of photons hitting the film.  All you do is pick a pair of settings that does what you want. Use a small f-stop (f16) combination for lots of depth of field (focus) in landscapes, and a short shutter speed combination (500th or above) if you want to freeze something moving in the shot.

close up dial of light meter

Pic of closeup dial

Incident versus Reflected readings

At this point, I am going to potentially confuse everyone by mentioning “Incident light”.  When you point your meter at the thing you are photographing, you are measuring the light reflected off it.  That is fine if the scene in front of you contains an even mix of tones, from light to dark (most do not). This is called a“Reflected light” reading.  This can give misleading results if the thing you are photographing has lots of light tones (snow scenes or beaches) or lots of dark tones (Huddersfield on a rainy Monday morning).  The miraculous answer is “Incident light” readings, that measure the light falling on to the scene, and ignores whether the tones in the scene are light or dark. It puts the settings right in the middle of the range of tones available so your negative will have a true representation of the scene as it looked when you fired the shutter.

photo of incident light meters

Incident light meters

To achieve this small miracle, the meter has a device called a “diffuser” that is placed over the light sensitive cell.  Some meters have big attachments like the Weston “Invercone”, usually referred to as “the poached egg” or a little slidey white hemisphere like on the Gossen Lunasix or the Sekonic 308 electronic meters.  The effect is the same, it mixes up the light are measures the brightness of the sunlight, or studio light or whatever and translates that into an accurate exposure reading. Motion Picture Lighting Directors have used nothing else since the 1930’s, by the way.

photo of hollywood picture light meters

Hollywood meters “Classic Motion Picture Meters”

To use the “incident light” method, put the diffuser over the meter measuring cell (the bubbly glass or round black circle) Go to the thing you are photographing and point the meter at the camera.  ( I know this sounds crazy but bear with me) Take the reading. Now you have measured the light falling on the thing, not the light reflected off it. If you can’t go to the thing and stand by it (Mount Fuji) or it isn’t safe (Hippos on Safari), if the light is the same where you are as where they are, just point the light meter at the opposite direction to them and take the reading.  Some people point the meter at the light source (the Sun or brightest part of the sky etc) but that is wrong unless you take another incident light reading in the opposite direction and average the two readings (This is a more sophisticated method and is only used if using very exposure fussy films).

sixtino light meter aligned ready to go

Sixtino with fstops and speeds aligned

So now you have your reading, say you choose f11 at 125th of a second, just set the camera to that and shoot away!  Unless you move into shade or a building, or the sun comes out from or goes into clouds, you don’t need to keep checking your meter, the light won’t change very much and constantly checking your meter disturbs your creative flow.


Where do I get one and how much?

You can get cheap and good meters on Ebay for very little money in comparison to what they originally cost.  Selenium Cell meters don’t need batteries, CDS cell meters do need batteries and some need special batteries that are hard to find.

Selenium Cell Meters

A good Selenium Cell meter like the Weston Master V or Euromaster will only cost around £20, make sure it has the Invercone” attachment.  Other good Selenium-Cell meters are the Sekonic 398 or 286 (essentially the same thing) at £35-£55 – make sure they have a “High scale slide”, a round bubble diffuser, and a flat diffuser.

Sekonic light meter

L398 Sekonic

These are great meters and won’t let you down, but they are a bit bulky.  The Zeiss Ikon “Ikophot” is a beautiful little Selenium meter in a leather case that has a slide-on flat diffuser.  Usually quite cheap, £20 ish - make sure the diffuser slide is with it. The Gossen “Sixtino” is small and accurate, comes in a Panzer Tank-proof case, and used a sliding venetian blind looking thing to change from reflected to incident light readings.  Still cheap at £40ish. The Gossen “Pilot” is similar.

CDS (Electronic) Meters

photo of electronic light meters

Sekonic L308 pic

For CDS electronic meters, a good modern one is the Sekonic L-308, in all its variations.  Takes normal batteries, is small slim and neat, has a sliding dome diffuser and is dead accurate.  Expensive around £85.00 or so. Any of the battery powered Gossen meters (Lunasix, Bisix, Sixstar, Lunalite,) are good ,but they take a 1.35 volt battery, not 1.5v which you have to buy on-line. Not a deal-breaker, they last about a year.

For now, that’s enough info, I may follow up with a discussion on “Contrast Range Metering” a method used many film cameramen and lighting directors, to find out what the contrast range of the scene is and adjust the lighting to compensate (think using a hand-held reflector outside in daylight if photographing a person) and I might even go on about “Expose for the Shadows, Develop for the Highlights” for those of you who can develop your own films. (That was how Ansel Adams did it).

 

*Sunny 16 Rule

The basic rule is, "On a sunny day set aperture to f/16 and shutter speed to the [reciprocal of the] ISO film speed [or ISO setting] for a subject in direct sunlight." For example:

  • On a sunny day and with ISO 100 film / setting in the camera, one sets the aperture to f/16 and the shutter speed to 1/100 or 1/125[2] second (on some cameras 1/125 second is the available setting nearest to 1/100 second).
  • On a sunny day with ISO 200 film / setting and aperture at f/16, set shutter speed to 1/200 or 1/250.
  • On a sunny day with ISO 400 film / setting and aperture at f/16, set shutter speed to 1/400 or 1/500.

Credit Wikipedia

About the Author:

Howard Maryon-Davis is a photographer and printer who has been working in darkrooms for over 40  years.  For all of that time his lab was based in central London, and printed work for many of the top names in advertising and editorial photography.  Now semi-retired, he still keeps a darkroom and studio going, and does a bit of teaching from time to time, mostly black and white printing using all the old techniques that have been handed down for many years. He is based in Devizes, Wiltshire, a few miles from Avebury. If you're interested in learning more about darkroom printing then head to his website for information about lessons: http://www.devizesdarkroom.co.uk/ He is also on Instagram as @howardmaryon

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