I have just purchased the light meter and need your help in using it. When putting the white diffuser on to measure incident light, shoudl I point the diffuser to the light source or point to the camera - it takes difference readings when pointing to the light aource and to the camera, which way should I go? When measuring the EV, should I put the diffuser on? Many thanks for your help. Taking the chance, may I wish you all here have a Merry Christmas and prosperous year 2002 and beyond.

-- tom tong (tom.tong@ckh.com.hk), December 23, 2001

Answers

I too use an incident meter, they are very acurate but only with some careful thinking and practise/calibration. Generally the meter is held with the dome in front of the important area of the subject and pointing back to the camera. You will find that the angle at which you hold the meter can alter the reading by a stop or more.

Say, for a landscape you hold the meter vertically to take a reading, with my own Sekonic I must tilt it down by around 30 degrees or the meter will tend to indicate an under-exposed shot. Similarily you will find that altering the meter's position horizontally will change the reading significantly.

For a backlit shot I find a reading from the subject towards the camera (ie away from the light source) may be slightly over-exposed, in this situation it may be better to hold the meter at right angles to the light source and camera.

This is tricky to illustrate without diagrams, the best bet is to use a slide film and take a series of test shot with wide brackets (+/- 1 or 2 stops) and guage your readings by the results.

No two meters will normally give exactly the same reading in an identical situation, you need to 'learn' your own meter. And most importantly, buy a good book on exposure technique with incident meters where all this will be explained with much more eloquence!

-- Giles Poilu (giles@monpoilu.icom43.net), December 24, 2001.

Incident meters are very easy to use. To keep it simple, meter from the subject with the dome pointed toward the camera. If the subject is difficult to get to, just hold the meter in the same type of light as the subject is getting. In difficult contrasty lighting, you have to decide which part of the subject is important to you and point the meter to whatever light source is lighting that part.

-- John Collier (jbcollier@powersurfr.com), December 24, 2001.

Tom,

I was answered a similar question today so you might also be interested in this thread on incident metering technique: Incident Metering: A different approach. If you read through it you'll find John Collier's answer summarizes it very well.

-- Bong Munoz (bong@techie.com), December 24, 2001.

I have to diasgree - I have just read the above link and as implied in my first answer, it is NOT simply a case of holding the meter in a certain place and taking the reading as gospel. As I said, hold the meter vertically then tilt it down then up and tell me the reading doesn't change! If you aim the dome at the light source (ie the sun) your subject will be under exposed. My meter was calibrated and checked by Sekonic last week, but the angle at which readings are taken is crucial.

-- Giles Poilu (giles@monpoilu.icom43.net), December 24, 2001.

I won't feed this particular fire by trotting out my own incident metering technique. However, I disagree with the statement that pointing the incident dome at the sun (light source) results in underexposure. Assuming you're rating the film at your tested EI then pointing the incident meter at the sun results in correctly exposed surfaces that are facing the sun. If the shadow reading is beyond the film's latitude then surfaces facing away from the sun will be dark with little or no detail. This does not mean that pointing the incident dome at the light source is wrong or underexposes the scene -- it simply means that you have to take a shadow reading as well and choose an exposure that falls in the film's latitude, sacrifice either highlight or shadow detail, or modify development to account for intentional overexposure.

Angling the meter so that the dome is only partially lit by the main light source is just another way to balance the exposure between highlight and shadow detail. It works but it's a technique that each one has to work out by him or herself.

-- Bong Munoz (bong@techie.com), December 24, 2001.

Bong - no point in re-arguing the same points that were debated in the link you provided. Thanks for this link - the best debate I have ever read on incident (and general) metering. I actually printed out all 20 pages of it so I could study it properly.

Sufice to say no-one could agree on the absolute correct method of metering but one thing is CERTAIN - it is not simply a case of holding the meter at X pointing it at Y and bingo! perfect exposure. John is a pillar of wisdom but here I am afraid a simplistic answer just will not do - it doesn't work! If anyone doubts this take a slide film, take a whole range of varied light shots from indoor to backlit to sunset to midday to fill flash etc using straight incident metering and many will be un-satisfactory.

I really would implore Tom to read the link and (if I may be so bold) take my advice which is repeated more than a dozen times by various people in the thread: "Use the meter with intelligence"; "use your brain even when you're using an incident meter"; "no one method will give the 'correct' reading"; "test shots with tranny film, pick a system, calibrate it, use it"; "bracket, bracket, bracket"; "I can't simply take an incident reading as the correct exposure"; "incident metering sucks"; "very careful to interpret the results, not to accept them as gospel"

etc, etc, etc. It's 11 o'clock on Christmas eve, Happy Christmas and good night!

-- Giles Poilu (giles@monpoilu.icom43.net), December 24, 2001.

I've been using an incident meter to measure nearly all of my exposures since 1985. The way I've thought of it since day one is "use the meter to measure the light falling onto the white hemisphere".

Wrap your brain around that, it is very simple and accurate to use. Indeed, far more so than any reflected meter (which you always have to compensate for the subject's colour, reflectivity, backlighting etc.)

-- Andrew Nemeth (azn@nemeng.com), December 25, 2001.