How To Shoot A High Key Photography Background

I am regularly asked - by annoyed photographers - what materials they should be using to generate a crisp, sparkling, pure white photography background.Unfortunately, that often is the wrong question to pose! It in reality, is not the backdrop material that offers you the clean white you might be seeking.It is the source of the light!Here is the case…you set up a sterile white bed sheet or a roll of white paper - and you situate your model in front of it.You set up a light source or two and light your model. All is looking nice.  You think you've got a properly lit model and a pleasant white background.Now, you shoot the picture.Anxiously, you dart to the photo lab if you are shooting film or to a computer if you are shooting digital. You see the finished photo and ta daaa! Your subject matter is flawlessly lit, however the backdrop is usually a dull gray color. Not the sterile, pure white you saw contained in the viewfinder!Seem familiar? If you've been having a hard time with your high key photographs…And you have been creating that dingy gray color (no matter what materials you employ) here is how to fix the situation!All light has a certain fall off factor.By that I mean the further the light is from a subject matter, the less bright it appears. Thus, meaning… if you have a certain quantity of light striking your subject matter, and you're using that SAME light to light your backdrop, your light is further away from your backdrop than from your model. Therefore, it is going to be a little dimmer when it gets to your background substance. Whew! That's a mouthful. In other words...The main reason you're shooting that gray color is because there is more light striking your subject than is hitting the photography background. To have your backdrop be a genuine, flawless white…simply hit it with MORE illumination than you are using for the model!Seems obvious as soon as you understand it, but this can be a huge sticking point for many shooters.The amount of "over-exposure" you will need for the backdrop depends upon the color of the backdrop material. If it is already white, you could get by with using enough extra light to have an over-exposure of approximately half an f-stop. Possibly even one full f-stop.If the material you are beginning with is gray…that's OK too! Simply hit it with roughly 2 ½ stops (give or take) more brightness than you're using on the model. Here's one that may blow a number of minds…what if your photography background fabric is really a pure black piece of material - or black paper?It does not make any difference! Zap it with 5, 6 or possibly even 7 additional stops worth of illumination (over what you happen to be using for the main subject) and you'll once again have a pleasant spotless white setting. This is a BUNCH of light and I wouldn't advocate starting out with a black backdrop. When you start nearer to white in the beginning, it is a lot less difficult. Nevertheless, try it! It is a fun experiment and can educate you quite a bit on the subject of light!The point is - with enough light, you can get a nice white photography background no matter what type or color material you start with.