High Key in photography refers to a method of lighting the subject and to a particular kind of image. There are technical explanations and aesthetic all over the net, and little agreement about what the terms do mean or even what they should mean. This Intel is not intended to add to the confusion. Please read it as an explanation and an approach to achieving a particular look in a photograph. If you understand High Key to be something else, that’s fine. These techniques will still produce the kind of picture I am interest in describing, and you can offer an alternative name if you want to.
History - The term High Key originated in early cinema to describe a system of lighting that minimised contrast (which made life easier for directors and cinematographers). The basic lighting design used a fill light and backlight set-up, with the key (main) light placed high to avoid shadows and the key and fill lights adjusted so that brighter areas were no more than 3x lighter than the darker (a 3:1 lighting ratio).
Defining a High Key Image - In photography, high key lighting is used to produce images with tones that fall between white and gray, with very few dark-grey or black tones. Those darker tones have to be strictly limited for the image to be true high key. The pupils of your subject's eyes in a portrait or the black dots on a white dice would be completely acceptable. A subject posed against a white background wearing a black dress would not.
The defining high key images are probably a white seal cub on the ice pack or the bride in a white gown on a white background.
For the purposes of this Intel, high contrast images are not considered high key and nor are overexposed images; High Key requires the same care with exposure and contrast as any other photographic approach.
Low contrast images are not necessarily high key either. More often, they are just dull, poorly printed or flat photos. A high key image should be full of life; between the 18% grey and pure white, it should show a full range of tones. That isn’t possible if the picture is overexposed: that is not high-key, and nor are blown highlights an aspect of high-key photography, which is really more attuned to subtlety – which means that blown out backgrounds are not necessary for high-key, either.
Suitable Subjects – Any subject that has a good tonal range can be approached in a high key way. High-key images are basically light-toned but it is as much a question of mood as of subject and high key can be open, expansive and energetic or cool, romantic and dreamy. Think first how you want to show your subject, then decide the lighting you need to achieve the look. If high key will achieve this, you have your subject. In other words, subject first, lighting second! Approached this way, a black cat may be easy to light in high-key style, but at doesn’t mean you will finish with a high key photo; but anything less dramatic should be fine. The obvious subject is a portrait but table tops, still life and product shots, macros and pets all lend themselves to this approach.
Equipment Since your lighting is pretty simple, not a lot of equipment is needed. You need a light background, preferably white, which you can light separately to your subject, and a light for your subject (we will come to the details of setting these up later). You can manage high key lighting with window light and a reflector, but you will have more flexibility if you have access to flash, soft boxes or umbrellas because they deliver wide, even light that helps illuminate the background properly. Fixed lights are fine, too.
:Lighting Technique – High key requires a lighting ratio not to exceed 3:1. The fill light should be 1/2 the main’s intensity (i.e. about 1 f/stop less bright). If you don’t have a separate meter, don’t worry; we’ll sort that out later.
Back Light - To make the appropriate pure white background, we are going to over-light it relative to the subject, so start with a simple white background and put one or more lights onto it. Using head and shoulders as an example, simply place a flash unit or white light behind the subject, aimed at the (white) background.
Take your reading from your subjects face. What exposure the background gets doesn’t matter so long as it is between 2/3rds to 1 stop more than this. If you go brighter with the background light, you will get ghosting on the edges of the subject, which does not belong in a high-key photograph.
The main trick with the background is lighting it brightly and uniformly. Moving the light away from the background reduces the light intensity and to gives a more even effect. Moving the light (or background) is also a simple way of adjusting the exposure on it.
Main (Key) Light - The key light produces our modelling. Place it light high to simulate the sun. Usually this main light is set slightly off to one side so it isn’t quite full frontal lighting. This achieves fine, delicate, modelling shadows.
Fill light - You don’t want deep shadows, so soften them with a fill light or reflector. This is accomplished by placing the fill at camera height near an imagined line stretched between camera lens and subject.
Again, set the fill one stop lower than the main. If you don’t have a meter, use lamps of equal output. Measure the main to subject distance and multiply by 1.4. This will tell you how far to place the fill from your subject if the lights are of the same power. If main and fill are identical and set equidistant, a 2:1 ratio results which is too flat.
Getting the Exposure Right Turn off all the lights except the fill. Take a reading with a separate meter if you have one. Set he camera to this value. If you don’t have a separate meter, place your camera on your tripod in the shooting position, set aperture priority, depress the shutter half way and note the settings. Switch to manual and make sure the same settings are still set.
Turn on all lamps for the shoot using fill only settings and make a trial exposure. Refine this exposure by bracketing using 1/3 f/stop increments. If you are not happy with the results but your main subject is well exposed, do not alter your camera settings! Adjust the light on your background. You can move it closer to the background if it is not white enough, further away if too bright.
Good high key photographs maintain edge separation between the subject and the white background while filling the shadows just enough to give detail. Now you have the technique, the photo is up to you.
