High Key photography has been around for years, and if you peruse the 'net you will find lots of images that are
called high key but they are not. Answers.com uses the following definition for
high key lighting;
"In photography, lighting that produces tones that fall mostly between white and gray, with very few dark-gray or black tones." In the digital age this translates to all tones in the image will be above 128 with the exception of [a]
few black tones. These few could be for example the pupils of the subject's eyes in a portrait. This would not include a subject wearing black slacks posed on an all white background.
The quintessential high key portrait image is a bride in a white gown on a white background. In my first image below everything falls above 128 except for her pupils, the green leaves of her bouquet, and the shadow on the left side of her face. The second image is a true high key image.
If you type in
high key photography into any search engine you will find lots of photographers calling
high contrast images high key, and
overexposed images being called high key, but these are not true traditional high key images. I have posted examples of these images below.
You don't
have to put more light onto the background than what is on the subject (my high key bride's background was lit by spill from the main and one small background light) but for a
pure white background you
will need to.
The question is, how much light is required to make a background pure white and how is it done? There are numerous ways. Most photographers start with a white background and put one or more lights onto it to overexpose it (overexposed when compared to the exposure used on the subject.) If you are shooting a head and shoulders image you will not need as elaborate a lighting system when compared to what is used for a full length image. For a head and shoulders high key background simply place a flash unit behind the subject aimed at the (white) background and make sure it meters 2/3rds of a stop more than the shooting aperture and the correct exposure for the subject's skin. Obviously in any type of portraiture (except high contrast) the aperture of the camera must match the meter reading of the main light, otherwise you will wind up with an overexposed subject.
Here is how I do my high key images. My high key camera room has a white ceiling and black walls. The black walls prevent my background light(s) from striking them and bouncing light off of them and affecting my fill light exposure, and also the shadows on my subject. Some light does bounce off of the ceiling so I use it as my hair light.
My fill light reading with the
fill and
background lights both on is F 5, and my main light reads F 8 (with the dome pointed toward the main light only.) My background lights read F 10
at the subject. I take
ALL meter readings at the subject, so for my background light reading I place the dome of the meter right beside the cheek of the subject
aimed at the background and I take my reading. I don't really care what the reading is on the
background I only care what it is
beside the subject. It must be between 2/3rds of a stop to one stop brighter than what the main light reading is. If you put two or three stops more light onto the background than what is needed you will get ghosting on the edges of the subject. So with the main light reading at F 8 and the camera aperture set at F 8 (for properly exposed skin) and the background light metering at F 10 (2/3rds of a stop more than the main light reading) the background will be overexposed (255) which is white no detail. The difference between F 8 and F 10 is 2/3rds of a stop.
Benji