Correct Sunny 16 Technique?

[Andre Noble]

I am trying to get a correct meter calibration as a starting point for proper ASA setting to use on my Sekonic L-358 with the purpose of making more accurate transparency exposures.

I am already familiar with the "1/ISO @f16" Sunny 16 rule which applies during the time of day 2hrs after sunrise or 2hrs before sunset on a sunny, cloudless day.

However, from all the threads I've researched, none has mentioned WHERE the dome of incident meter should be properly oriented in relation to the sky. The readings one gets vary widely based just on that!

Ie, does one hold the meter perfectly vertical, with dome directly toward the sun's direction? Or does one have the meter held at an angle up slightly with dome's center directly pointed at Sun's center? Or is the meter held horizontal with dome point perfectly straight up into the sunlight sky? Or is it "none of the above"?

Expert advise appreciated!

[Tim Curry]

No expert, but I think you would point the dome at the lens itself. The meter is trying to decide how much light is falling on the subject. If you point it at the lens from the location of the subject, you are reading the light falling on the subject.

I use reflective metering, so please correct me if I am wrong about this technique.

[Michael Mutmansky]

Incident meters are deceptive tools to use. It seems like an easy thing, to simply hold the thing up, and get a reading that tells you an exposure for the subject.

However, that is truely a gross oversimplification of what it does. In most cases, the meter uses a small dome (sometimes called an integrating dome) to collect and average the light that the subject is receiving FOR A SPECIFIC ORIENTATION. This is the key to understanding how to use one well.

The orientation of the head determines a plane for which the meter is establishing an exposure. If you orient the meter with the dome pointing vertical, you are reading the exposure to correctly expose for a horizontal surface (like a table top).

If you orient the meter at the subject pointing toward the lens, you get a reading for a surface perpendicular to the camera at the point of the meter. This may not be the best orientation, depending on the subject and lighting conditions

If you point the meter directly towards the sun, you get a reading for a plane perpendicular to the sun, and will almost certainly end up underexposing the subject, except in some cases.

There's many approaches on how to meter, but I think the best way to do this is through some personal trials. When photographing a three dimensional subject, there may be several orientations of the meter that seem to make sense. Take the meter readings for the various orientations and then think about how these meter readings relate.

You could try an exposure for each meter reading and then analyze the results and see what seemed to work. What I do is consider the readings, and then do an average exposure based on the various readings that I get in the meter.

Often the lighting is such that there is little difference in the readings, as in situations where the primary light source is behind the camera (like during a sunrise/sunset). However, even in these conditions, a building surface pointing directly toward the sun will have a higher light level than one pointing 45 degrees to one side or the other. You still have to decide what surface you want 'correctly' exposed, which is where the averaging come in.

If you want both surfaces exposed well, then a true average of the two might be about right. However, you could also decide that you want one correct, and the other to either go dark or light. You might then strongly weight the exposure toward one or the other readings.

For general scenic work where there is no real orientation to the subject, I will typically take a reading towards the light source, and then away at about 90 degrees, to get a sense for the difference in exposure, and then I'll find a point in the middle, generally toward the highlight side to avoid overexposure of the highlights.

Another way to get a sense for the exposure is to orient the meter vertically towards the camera, then take a reading. Then, hold your hand over the sun, so it cases a shadow on the dome, and take another reading. These give you information on the primary light, and the light that results from the sky and reflection off the ground. Again, these can be used to determine a reasonable exposure for the subject.

Everyone is different with meters though, so you will need to develop a procedure to determine how to get accurate readings for yourself.

It goes without saying that there will be an orientation where the meter will actually give you the reading that you desire without having to average several. With some experience, you may find that you can do a good job approximating the ideal exposure by considering the various issues with the subject, and then selecting an orientation that takes them all into account.

---Michael

[steve simmons]

If you have reflected metering capability why use the incident method. It runs the risk of poor exposures in contrasty situations and does not give you an idea of the overall contrast range of the scene which you need to know regardless of the type of film you are using.

steve simmons

[Andre Noble]

Thanks Michael for taking the time to make a detailed post. But my question pertains to calibrating my Sekonic L-358 incident meter to the sun as a reference standard, and how to do that specifically.

As it stands now, my meter consistently underexposes different transparency emulsions, despite good metering technique. This is in line with it's reputation as expressed by other photographers on photonet, etc.

But perhaps I should just take a film that's known to be rated accurately (such as the Kodak 100S transparency film) and calibrate my meter to proper exposure of that, instead of calibrating to the sun - although some swear by calibrating to the sun using the Sunny 16 rule.

[Andre Noble]

Steve, you're right. I use the incident meter for LF portraiture and (dare I say it) a lot with 35mm and MF handheld - and just wanted to see what info I might get from this LF group.

[Nick_3536]

Sunny 16 is a way of estimating exposure for an object lit by the sun. So the meter must be lit by the sun. If you hold it up then won't the bottom of the dome be in the shadow of the top of the dome? Tilting will help some. But if you hold it out flat in the palm of your hand the sun will hit the whole dome. Makes sense? Maybe just to me. Basically you don't want the light casting any shadows. I don't have any sun or I'd check for you.

[Ralph Barker]

To paraphrase dear old Obiwan, "Meter the light, Luke. Meter the light." ;-)

In other words, pointing the axis of the incident dome at the light source will give you an exposure reading that will render the "true tonality" of that portion of the subject exposed to that light. Whether that is the optimal exposure for the subject is a separate question, of course. But, for the stated meter calibration purposes, that may be the best method. An alternative method would be to take a reflective reading off a new (unfaded) 18% gray card held perpendicular to the light source (the sun in this case) under the appropriate conditions. Then, validate that base calibration with equipment and film tests.

It seems, however, that "proper metering technique" is highly subjective. Asking that question to six different photographers usually produces at least eight different answers. ;-)

[Steve J Murray]

I think the incident meter is great for metering portraits, where its much like taking a spot meter reading off a gray card in front of the subject's face. It will accomodate multiple light sources or other complex lighting situations. Metering a landscape is much different, and to me the incident meter is not as useful. After all, the subject is infinitely broad, and you have to take into consideration shadows and highlights that are all over the place. At any rate, if I were going to test an incident meter, I would use a human subject and go for accurate skin tone, or maybe meter and shoot a gray card. That would at least tell you if your meter is over or under exposing for a known and predictable subject.

[tim atherton]

And of course the sunny f16 "rule" depends/varies on latitude and time of year.

I remember reading once the (probably apocryphal) anecdote that Kodak calibrated it's film speeds by taking a grey card reading on a sunny day at mid day in mid summer in the Kodak staff car park at Rochester - and that was the standard/baseline....