selmslie Loc: Fernandina Beach, FL, USA

There are several factors that influence the brightness of an image:

1. The brightness of the light
2. The reflective properties of the subject
3. The aperture
4. The shutter speed
5. The ISO

The first and most important is the brightness of the incident light. It can be quantified as Light Value (LV). For example, the brightness of full sunlight during the middle of the day in temperate or tropical latitudes can be considered nearly constant. For reasons that will soon be apparent, let’s assign it a value of 15.

* Taken from the Wikipedia article on Exposure value where you can find additional information.

The second factor is the reflective properties of the objects in the scene, how much of the incident light is reflected. This ranges from very high (for snow, white clouds, white paint or white feathers it can be 90% or more) to very low (a pile of coal might reflect 10% or less). But you want to render these subjects as bright and dark. Your camera's meter will try to render them as middle gray. That would be wrong.

Here is how we end up at LV=15.

Shutter speeds starting at 1 second are given a value of 0. Each doubling of the shutter speed increases that value by one:

For longer shutter speeds the value becomes negative.

Apertures starting at f/1 are given a value of 0.


When you combine the value for the shutter speed with the value for the aperture you get the Exposure Value (EV):


ISO values starting at ISO 100 are given a value of 0.


When you combine exposure value with value for the ISO you get the Light Value (LV).

LV 15 is substantially in agreement with Sunny 16 which recommends 1/ISO sec @ f/16 - LV=14.67.

Since the value for ISO 100 is 0, the exposure value table for ISO 100 can be used as a light value table.

Knowing all of this you can learn to set your ISO and exposure without looking at your meter.

selmslie Loc: Fernandina Beach, FL, USA

* Taken from the Wikipedia article on Exposure value where you can find additional information.

Fotoartist Loc: Detroit, Michigan

I use Auto ISO a great deal of the time after intelligently setting it which allows me to more fully concentrate on the subject and composition at hand. Exposure is not a great problem as it was in film days.

selmslie Loc: Fernandina Beach, FL, USA

But that means you are still letting the camera determine the image brightness based on reflected light. That can get you into trouble and force you to use exposure compensation.

BebuLamar

To the OP!
With all due respects the technique you posted relying on known brightness works well as well as using on incident metering works well. But others do use reflected light metering technique and it works well for them too. In fact for some when when using known brightness values they depend o. n luminance instead of illuminance

selmslie Loc: Fernandina Beach, FL, USA

You are missing the point.

How many times do you need to take an incident light meter out into direct sunlight before it dawns on you that you keep getting the same reading?

The definition of insanity is doing the same thing over and over again and expecting a different result. (Commonly mis-attributed to Einstein)

The point I am making is that you don't need a light meter at all - incident or reflected - to get a good exposure in daylight.

For that matter, you don't need one for any of the conditions listed under LV 15, 14, 13, 12 or 11 above.

And your camera's meter can fail to produce a useful exposure at LV 10 and below because it can be confused by the wide DR and the presence of light sources in the frame. Under these circumstances you may be better off relying on the experience of decades of professional and amateur experience than on your camera's meter.

You are better off simply picking an appropriate LV and then just looking for flashing highlight warnings.

I use LV 15 all of the time in daylight. My highlights are never blown and even most of my JPEGs SOOC are very close to my final results. Just look at my web site.

It's common sense.

BebuLamar

You missed my point. Your technique which relying on known values is valid and these values are arrived at by using incident measuring (if things don't change you only need to measure them once).
There are other people who rely on reflective metering and if they rely on a known value they rely on its luminant and not illuminant. Their technique is also valid.
However, I have to disagree with you on the "Common Sense". For me there is no such thing. Whenever, I teach someone I always said park your common sense outside please.

selmslie Loc: Fernandina Beach, FL, USA

None of those values were established by using incident metering. They were all arrived at by trial and error. It also happens that digital ISO is actually derived from Sunny 16, not a coincidence.

srt101fan

Scotty, what oh what is wrong with using exposure compensation? 😕

User ID

Another tempest in a teapot brought to us by “the usual suspects@.

selmslie Loc: Fernandina Beach, FL, USA

When you use exposure compensation you are already conceding that the camera's meter is wrong.

How long before you learn not to trust the camera's reflected light reading in the first place?

bleirer

It is interesting to see how those EV's are calculated. It always gets me that higher EV is lower exposure but higher EC is higher exposure, reducing EV. I guess that's a use for P Mode. Lock it in and scroll the wheel for all combinations at that ev.

Proves there is more than one way to skin the white cat in a snowstorm on a sunny day.

selmslie Loc: Fernandina Beach, FL, USA

EV seems counterintuitive at first until you get to light value.

Then higher LV means more light and lower LV means less light.

srt101fan

This is where I think you are very wrong. You view your camera as something that makes decisions and tries to force them on you, a contraption that is often wrong and can't be trusted....

The camera is NEVER wrong. Unless it's broken, it does exactly what it's designed to do. It's the photographer's responsibility to understand how the light meter works. Use the meter's output as a starting point and adjust the camera's suggested settings as necessary. Exposure compensation is simple, effective and very useful.....This is the 21st century, why would I want to carry around or memorize a bunch of tables with numbers?

bleirer

In a way, evaluative metering tries for something similar by using a database of possible scenes to adjust the exposure. Canon doesn't tell me their secret sauce recipe, but I bet they use the focus point for weighting and try to match common scenes such as backlit sunny day, etc.

Personally I don't meter, but watch the histogram in the viewfinder and judge from there.