In today's world of Auto every thing
Most photographers need reminded how
light meters are calibrated (what the heck does this have to do with proper exposure, keep reading).
All light meters are calibrated accurate based on light reflected off of 18% grey
So if you are photographing anything other than 18% grey, your images are going to be Under or Over exposed. Unless you take control of the exposure by getting the camera set to Manual exposure
or use Exposure compensation.
For example if your are using auto exposure (AV, AT or Program) and you are photographing a white sweater, that white sweater is going to be under exposed and not look so pretty white
Because the light reflected back to the camera is going to be much brighter than the same light reflected of of an 18% grey card and the camera is going to think there is way too much light and make the aperture smaller and the shutter speed faster than need be.
So what does a person do to get accurate measurements of light:
Get a hand held light meter and while you are at it get one that reads flash as well as ambient light
I recommend a Sekonic L-308S for @ $202.00
You will use this meter to meter the light at your subject and the light should be metered as it
is falling with the white dome of the meter over the light sensor
(This is called an Incident Light metering Technique)
Get an 18% Kodak grey card and make sure you meter the light at the subject that is bouncing off
of the grey card only, not part of the subject or the background
the grey card. An Expo Disc is also a good suitable substitute for use of the grey card (although a
bit more pricey)
Once you have metered the reflected light off of the grey card or metered the Incident light with your new light meter, you can switch to Manual setting versus Auto and set your shutter speed, aperture and ISO to that of what you metered and the subjects will be properly exposed.
An added benifit of metering the light (properly) reflected (without glare) off of the grey card
or using the Expo Disc is that you will also have the perfect image to use for White Balance (WB)
But WB is another topic for a thread later this year in this blog :)