Tag Archives: spot metering

Using light meters intelligently

First posted 21 April 2011

Looking at an analogue or digital hand meter for the first time can be very confusing, there are many options and often an overload of information. There are multi metering modes on advanced modern digital types which I find confusing even after using meters for thirty years, so I thought I might write a little about how to simplify matters and ensure consistent results.
Firstly, whatever you point a light meter at is read by the meter as a mid grey. It does this so that the whites are white and the blacks are black and to do that, it puts the exposure in the middle. To make this work, there must either be a range of brightness in the scene, or something which is already a mid grey.

Any and all light meters do this, and this is why when shooting in snow the hurried metering method often gives grey and underexposed areas where white should be the predominant tone. Another common mistake amongst beginners is to take shots looking up at trees or buildings without thinking of how bright the sky is. This causes the meter to read far too much brightness in the scene and the subjects end up as silhouettes against a grey sky. Even when a hand meter is used, false readings can arise from simple mistakes, such as having your shadow over the meter.

So let’s look at the different ways of metering; Reflected, Incident, Spot and Average.

Reflected is simply pointing a meter at something and seeing how bright it is, how much light is reflected from it. The problem though, is that if you point it at something rather dark, you will get an overexposed shot and pointing it at something light will give an underexposed shot.

Incident is a method which reads how much light is falling ON THE METER. This avoids the problems above. When using a hand meter, taking an incident reading will produce an excellent negative 99% of the time (it’s not much good with backlit subjects).
An incident reading is when a white plastic cone is fitted over the light cell allowing the meter to read light falling on the meter, rather than light reflected off the subject. The important thing is that the meter should be pointed towards the camera from the position of the subject, not pointed at the light source. If you are unable to stand in the position of the subject then simply point the meter in the same direction, but from a manageable position. As long as the direction of the light is the same where you take the reading and in the scene, the exposure will be the same.

One of the most reliable methods is spot metering. Not for taking a number of readings to average out the exposure as some meters permit you to do, as this can often lead to an incorrect reading (Because the important brightness is always two stops up from deep shadow, not half way between deep shadow and bright white). Finding the all important deep shadow tone, ( Zone III ) takes practice. If you can identify this tone in a scene and read it, you then underexpose that reading by two stops, which gives you zone V – which is two zones along. This may seem confusing, as the explanation is more complicated than the doing.

A simpler method is to set the spot meter to a film speed two stops higher than you are actually using, take a reading from deep shadow, set the camera accordingly and shoot. The film rating is not actually changed, so no alteration of dev time is necessary.

Because the meter is set two stops higher, it reads the shadows brighter than they are, the meter then suggests a faster shutter speed/smaller aperture. Shooting at this exposure causes the deep shadows to be two stops underexposed (from mid grey) which is exactly where you want them.

The explanation as I say often seems complicated, but in practice it is quite easy. give all methods a go and see which works best for you.

5 Comments

  1. Posted 02/05/2011 at 7:03 pm

    Thanks for this explanation. Although I’ve been using an old-fashioned hand-held meter for years, I did not really understand all the implications of this, and I guess I’ve just been lucky with my shots (though it does explain a few overexposed anomalies now), or fortunate to have been using film with a wide exposure latitude. My recent move into shooting slide film will probably be more telling!
    As my meter is so old, I’m guessing it’s measuring reflected light rather than incidental light – it doesn’t have one of those cones. Maybe I’ll have to start thinking about an upgrade to my kit.

  2. mark lacey
    Posted 06/07/2011 at 12:49 am

    For black and white your technique of spot meter deep shadow and open two stops is dead right, I’ve been doing that for 30 years and my negs have always been really easy to print, which to me is the point of the exercise. Don’t know anout colour, I don’t use the stuff! All good advice, it’s nice to see it expressed simply, some people turn the zone system into rocket science and I suspect in the process forget to take a good photograph.

  3. Posted 07/10/2011 at 9:35 pm

    I read Mark’s comment, and I had to stop and think about it for a moment. You wouldn’t OPEN two stops from the meter reading if you’re metering a deep shadow. The meter would look at that shadow and (as you explain so succinctly) give a reading to render it a middle gray – which would require either a slower shutter speed or wider aperture. Either way, in order to properly render the deep shadows properly using the spot meter technique described, you would STOP DOWN two stops – not open up… Your explanation of “underexpose that reading by two stops” is the same way of looking at the situation.

    I just wanted to clear it up because I put up a link to this great article, and then some questions as to whether the proper thing to do is OPEN the aperture – or stop down…

  4. Posted 05/04/2012 at 5:34 pm

    Thank you. These are some good insights.

  5. Philp Toal
    Posted 15/08/2012 at 5:29 pm

    I usually take a spot reading of the shadow area and over expose by 1-2 stops and develop N-1/-2 (depending upon the shadow area I want to show up), and then print down to Z3 because Z´s 1 – 3 expose as black on any paper unlike the the wider Zone range of say 1-18 of all films. Paper in general, barely goes beyond Z10 and with N development Z3 would render only black as well.