Are Incident Meters Useless?

Steve Absalom · March 25, 2009

We did our first student films this past week. We only had an incident meter and we would measure a scene like this:

We have lights. The lights read 1.4 where our actors were. So we put more lights until the actors read almost a 4.0 (try as we might, we'd pile on lights real close and it wouldn't get much higher). Now, since we were taught that in the zone system, the skin of a white person is generally a zone six, one stop above middle gray, we would then, taking our reading of ~4.0, set the aperture to 3.0 (it wouldn't go lower). In theory, we believed this would make the skin show up at zone six, exposing it properly. (We didn't have a gray card)

Then someone told us the Zone system was primarily for black and white film. We shot in color. Also, we were then told by another student filmmaker slightly higher in education level than us, that incident meters aren't important for what we were doing, spotmeters are. That the reflectance values for the face are such that they will most certainly be overexposed and may even come out as white blurs.

Is this true?

Bruce Taylor · March 25, 2009

That's a whole lot of information! Incident meters are in fact very useful, provided they are working, calibrated, and used correctly. If you have an incident meter then you shouldn't need a gray card for light readings, that's for reflected light readings (like a spot meter, for example).

It's tough in a school situation, because the equipment is often in poor condition, it's difficult to know if the readings are accurate. An quick and dirty way to get some idea of whether your light meter is accurate is to compare its reading to another one you suspect is accurate. There is also the old "Sunny 16" rule, which I always forget (you can look it up) that will give you an indication of accuracy.

Above all I think you need to shoot carefully controlled tests at different apertures with the appropriate color/grayscale charts with a human (for skin tones) in them. That's what the pros do. Otherwise you just don't have much to go on. Read books on the proper (accurate!) use of reflective and incident light meters. The Zone System can be a way to peg different reflectance values of objects and overall dynamic range, but it was created for b&w photography and the individual development of large format negatives.

Good luck, you'll get it figured out. It takes a little time and study.

Bruce Taylor

www.indi35.com

Ryan Thomas · March 25, 2009

It seems like you only overexposed it by a stop, so they won't be a white blur at all. You'll find that people will purposely under or overexpose their negative to achieve certain effects. If anything, you'll just have to print it down and come out with something a bit more contrasty than you were expecting. If you haven't already, you should check out the book "Film Lighting".

The reason he says spotmeters are useful for what you were trying to do, is because spot meters will peg your exposure at zone 5. So if you read the persons white face at f4 with a spot meter, you'll know that you have to open up to f2.8 to put it at zone 6.

What the incident meter is doing though, is it's reading a white object (zone 8) in the light. You shouldn't have to do any corrections to put that certain brightness value at the correct zone. As long as you use your incident meter in your key light, you should come pretty close to a properly exposed negative.

By the way, the sunny 16 rule basically says that at f16, your proper shutter speed is the reciprocal of your film speed. So if you're shooting with 64asa film, at f16 your shutter should be 1/64th of a second. Since you can't really set your shutter independently without creating other "issues", you would have to figure out that 1/64 is 1/2 stop difference from 180 degree shutter, which is 1/48th. So your proper exposure would be an 11/16 split with a 180 degree shutter. Sorta complicated, but perhaps it'll help you out if you're ever in a pinch.

Edited March 25, 2009 by Ryan Thomas

Chris Keth · March 25, 2009

It sounds like you need to ask your instructors to actually teach you how to use the different types of meters.

You overexposed by about a stop. It won't be the end of the world. The reason you overexposed, in short, is because you used an incident meter and then applied rules (the zone system) that only work when you're metering with a spotmeter.

Ian Cooper · March 25, 2009

...The lights read 1.4 where our actors were. So we put more lights until the actors read almost a 4.0 (try as we might, we'd pile on lights real close and it wouldn't get much higher)....

The difference between f1.4 and f4 is 3 stops. Each stop is a doubling of the amount of light on the scene. Assuming your lights are all of the same power rating, you would need 8 times the number that you had to acheive f1.4.

If you achieved f1.4 with just one light, then adding a second will immediately get you the extra stop to f2. You'll now need to add two more lights to get a further stop up to f2.8. You'll finally need to add four more lights to gain the final stop up to f4, total lamp heads pointing at the subject is now 8.

Assuming at f1.4 you might have had one lamp for a key, a reflector for fill, and one lamp for backlight. You'll need to gather together a total of 16 lamps to shoot at f4. In those circumstances you may find it cheaper and easier to just rent a more powerful lamp in the first place. After all, x16 lamps will also require x16 stands and x16 modifiers as well!

:

...oh, and as everyone else has said: If you want to meter the light falling on a person's skin and then compensate, you'll need to use a reflective meter (ie. spot). If you want to just hold the meter in the light and take a reading, use an incident meter.

The two end results should be the same, the difference will lie in your ability to interpret the scene and know how much compensation you need to apply to the spot meter reading. In most cases you can directly apply the reading from an incident meter with no compensation. A spot meter is used by pointing it at the scene being lit, an incident meter is used by pointing it at the light illuminating the scene.

Brian Drysdale · March 25, 2009

Incident meters are the workhorse meter when shooting films. However, you shouldn't confuse using the zone system with a spot meter, which measures reflected light and how you use an incident light meter.

If you wish to learn how to use spot meters that's a useful skill to have, but in practise when lighting sets an incident light is a much more useful tool to have for adjusting up each light. Then just use a viewing glass get a feel for how it will look on film and readjust the lighting as required (or work the other way, whichever works best for you). Although with modern stocks, just using the camera V/F can be pretty close.

You can directly use the incident meter reading for the lens setting, it's the same as taking a reflected 18% card at the same spot.

David Mullen ASC · March 25, 2009

Some useful information:

http://en.wikipedia.org/wiki/Zone_system

The Zone System involved measuring luminance / reflectance (thus needing a spot meter) and previsualizing what tone you want that subject to be represented as in a final print. It has limited use in color motion picture work because it's hard to expand and contract dynamic range to make the tones fall into the Zones you want (though with digital color-correction, it's easier than it used to be since you can manipulate gamma). But the basic concepts can be applied. For example, a spot meter assumes a subject has 18% grey reflectance (more or less, this can be argued) which is Zone 5. Generally in a normally-lit scene, a caucasian face may be rendered in Zone 6 (one stop lighter than 18% grey). But you may decide for creative purposes that the face should fall into a different Zone, maybe lighter or darker.

Trouble is that for motion pictures, we aren't talking about single still images, we're talking about a sequence of shots. You don't want to vary exposure shot by shot necessarily because you also want a consistent density to the negative for the scene. This is why basing the exposure more on the amount of light falling on objects in the scene (incident metering) will be less confusing than interpreting a lot of spot meter readings of subjects moving in and out of different light sources.

David Rakoczy · March 25, 2009

Film Lighting

Jonathan Bowerbank · March 30, 2009

...taking our reading of ~4.0, set the aperture to 3.0 (it wouldn't go lower)
...we were then told by another student filmmaker slightly higher in education level than us, that incident meters aren't important for what we were doing, spotmeters are.

I assume since you were able to stop down to a 3, that you were shooting on some sort of DV camera. In which case, a spot meter is more useful than an incident meter, since the camera itself used a spot meter. If your camera has various setting for zebras, you could try setting one zebra patter for around 70, and the other for 95. That way you can tell where skintones are correctly exposed, and where something in the frame is too white.

Brian Drysdale · March 30, 2009

I assume since you were able to stop down to a 3, that you were shooting on some sort of DV camera. In which case, a spot meter is more useful than an incident meter, since the camera itself used a spot meter. If your camera has various setting for zebras, you could try setting one zebra patter for around 70, and the other for 95. That way you can tell where skintones are correctly exposed, and where something in the frame is too white.

A stop of 3 sounds rather like a Zeiss T3 10-100 zoom shooting on 16mm is being used.

Steve Absalom · April 7, 2009

I assume since you were able to stop down to a 3, that you were shooting on some sort of DV camera. In which case, a spot meter is more useful than an incident meter, since the camera itself used a spot meter. If your camera has various setting for zebras, you could try setting one zebra patter for around 70, and the other for 95. That way you can tell where skintones are correctly exposed, and where something in the frame is too white.

We shot on 16mm film with a super 16 lens, I believe it was an Optex something or other conversion, 10.8mm to 60mm zoom lens.

Brian Drysdale · April 7, 2009

We shot on 16mm film with a super 16 lens, I believe it was an Optex something or other conversion, 10.8mm to 60mm zoom lens.

Yes, the Cooke T2.5 9-50 Varokinetal modifed to Super 16.

Interesting to see, if there's a big run on those still unmodified lenses when the 2/3" Scarlet comes out.

George Leon · April 9, 2009

We did our first student films this past week. We only had an incident meter and we would measure a scene like this:

We have lights. The lights read 1.4 where our actors were. So we put more lights until the actors read almost a 4.0 (try as we might, we'd pile on lights real close and it wouldn't get much higher). Now, since we were taught that in the zone system, the skin of a white person is generally a zone six, one stop above middle gray, we would then, taking our reading of ~4.0, set the aperture to 3.0 (it wouldn't go lower). In theory, we believed this would make the skin show up at zone six, exposing it properly. (We didn't have a gray card)

Then someone told us the Zone system was primarily for black and white film. We shot in color. Also, we were then told by another student filmmaker slightly higher in education level than us, canthat incident meters aren't important for what we were doing, spotmeters are. That the

reflectance values for the face are such that they will most certainly be overexposed and may even come out as white blurs.

Is this true?

NO it is NOT true. Incidents meters are the most trusted tool to a cinematographer. Just learn how to use it properly and that is it. Simple straighforward reading. It works beautifully! Overexposed or underexposed images are just result of the ineptitude of the cameraman. NO excuses here!

The Zone System was developed by Ansel Adams while doing his still photography and most importantly his ZONE system in chemical development and printing in black and white photography. So, forget about Zone System here.

Remember these an you will become succesful:

Motion pictures is an organic process carried out by gathering a storyline, directorial vision and Lighting technique along with a timeline, a landscape and the actor's blocking and delivery from your POV (point of view) to be translated by YOU! into a beautifull SEQUENCE of IMAGES (24++) NO into a single print, therefore debunking Zone System here.

So, your lighting has to be organic as well. If your first mark read f1.4, you need to have the proper filmstock ASA and proper lens (fast) to read f1.4 or T1,4. in the proximity. It is all matter of cinematic looks and a well exposed scene.

After you discuss the scene with your director and ascertain your filmstock ASA and lenses to use (prime lenses are faster than zooms) you will set your lighting order and ligthing scheme to those parameters.

Consider the lighting to use at the first mark (actor's blocking) and the whole set illumination including in both the light fall off reading. Walk all about and around your set and read every single lighting source and twick it (adjust) -focus, height, distance- to your lighting scheme and actor's blocking and off course FStop.

All this is done with an incident meter in your hand. Feel the light source falling unto you. It is to bright? Use a stand by person to evaluate the falling light. It is to broad? It is not enough? AGAIN Feel the lighting falling unto you-walk under it- It this lighting appropiate for the genre and storyline? Use a gaffer's lens, so you can to evaluate the source. Are the barndoors and focus knob of the source enough for the job?

RECIPE TO COOK A PROPER ILLUMINATED SCENE:

Choose, rate and oder your lighting sources depending of what type of scene (genre/storyline) your director wants you to illuminate. Add to the decision list, the correct filmstock ASA and correct lens choice (prime vs zoom). Draw in advance a ligting scheme (plot). Add and spice it with diffusers and gels to taste . Mix. Photograph it . Process at lab. (discuss prior shooting your plan with timer/DI). Print it. Project it. Become a famous D.P. No apron need it.

In your D.P bag you should carry an incident meter- Spectra, Minolta, Sekonic and a spotmeter,

same brands. Both meters will provide you the same reading. The only reason to use a spot meter is DISTANCE. If is out of your reach use a spotmeter, if is at your reach use a incident or reflected meter. That is it!

Spotmeter:

Diferent tools for different uses. Both read incident light falling (funny thing, eh!) into the subject. One for close reading and the other for far away reading. For some incident meters you can add the spot meter gizmo, like to an earlier Sekonic I used to own.

http://www.sekonic.com/main/

FOR MORE READING about CINEMATOGRAPHY visit,

http://www.filmcastentertainment.blogspot.com

Also visit KODAK to dispell any voodo or quack ideas about what is what.

http://www.kodak.com/cluster/global/en/con...dex.shtml#54248

Jim Hyslop · April 9, 2009

In your D.P bag you should carry an incident meter- Spectra, Minolta, Sekonic and a spotmeter,
same brands.

I presume you mean one of each type, not one of each brand :-)

Both meters will provide you the same reading. The only reason to use a spot meter is DISTANCE. If is out of your reach use a spotmeter, if is at your reach use a incident or reflected meter. That is it!

Wouldn't you also use a spot meter to measure the contrast in the scene? Read the darkest part, read the lightest part, and make sure the difference doesn't exceed your film (or video) latitude (unless you want it to, of course).

David Rakoczy · April 9, 2009

Are incident Meters useless?.. only when they don't have a battery in them...

Brian Drysdale · April 9, 2009

Wouldn't you also use a spot meter to measure the contrast in the scene? Read the darkest part, read the lightest part, and make sure the difference doesn't exceed your film (or video) latitude (unless you want it to, of course).

You don't need a spot meter for video because you can see instantly on a correctly set up monitor if you're exceeding the contrast range, plus you have zebras that do the same thing at 100%.

The spot meter is handy for the details like internally illuminated signs etc. but for the highlights and shadows the incident meter does place them in their natural relationship and by using a viewing glass you can see any areas of concern.

Although, the spot meter is useful if the dark tones or light tones are more important than the mid grey, but for 99% of general film work the incident meter is all you actually need. However, it's a good idea to have a spot meter or at least a reflected light meter in your light meter kit.

You should test your stock, so that you're aware of how well it handles under and over exposure. You can then walk around the set checking where you're under and over exposing with the incident.