The 4 Basics

[Loupey]

Before the age of instant feedback digital, we all had to be real careful about the exposure we set (unless we liked paying for a lot be horrible slides ).

I used to use these tools all the time when shooting with my medium format equipment (camera doesn't even have a built-in meter). The first one is my Sekonic L-398 incident light meter. Unlike your built-in camera meter which measures the light reflecting off the subject, this meter reads the amount of light coming down onto the subject. This takes out the variables of the subject and background (reflectivity, color, size, and proportion - all of which can fool the camera). Notice here that the meter reads a value of "80" which, for ISO200, gives one possible combination of 1/250s at f/8 (which is the same as the 1/250s at f/11 at ISO 400 used last week).

The other tool is an 18% gray card. This card costs a couple bucks and is used with your camera's meter to accurately record the light coming down. Basically turning your camera into an incident light meter like the handheld version above. Why this particular shade of gray? It is exactly halfway between pure black and pure white - this is how every camera meter sees the world.

In the two example shots, I switched to aperture priority mode (Av) to let the camera do its thing with a difficult subject. Straight out of the camera with no post processing. The first one is obviously too dark. Notice how the gray matches the 18% gray card? The camera tries to render all scenes towards 18% gray. Now I add the card in the scene so that the camera reads it and accurately adjusts the exposure accordingly.

These tools can still be used with digital. But not really necessary as long as your know what to meter off of. Any middle toned object will do - anything that is the color or shade (if you, like the meter, were color blind) of the 18% gray card. The card comes in handy when using extension tubes as there is a light loss so reading the card when changing tubes allows for simple exposure adjustments.

Underexposed/overexposed images look terrible, digital or not. Trying to salvage them in PS isn't enough to save them IMO.

Know the limitations of the camera.