Thursday, 8 April 2010

Colouring a Background with Strobist Collection Gels

Creating a coloured background using flash or continuous lighting and coloured gels is a technique that every photographer working with lighting should master. Many photographers strive to achieve a pure white, no dot or 255 white background, but rarely do you see people expanding their vision to add colour to their backgrounds. Adding colour to a background is simple to achieve whether you are using studio flash or even off-camera hot shoe flash or Speedlites. 


If you read my recent blog post on creating a snoot using Rosco Photofoil: 


http://ianpack.blogspot.com/2010/04/creating-snoot-with-rosco-photofoil.html 


You’ll notice that I coloured the background using a Rosco Strobist Collection Cinegel 85 full CTO gel held in place with a Go Pro Photo Gel Clip. Cunningly concealed at the back of the Strobist Collection are a series of useful coloured effects gels.


What follows is an introduction to creating coloured backgrounds with off-camera flash lighting. This is a technique I learnt back in the early 1990’s at a workshop run by Fuji Film. I forget who the photographer was and my notes have long since been recycled, but the technique was referred to as “Chroma Zoning”. 


Chroma Zoning
First of all I’ll show you how to vary the tone of your white background using just #375 Cerulean Blue and the flash output. The set-up is identical to the blog entry mentioned above, but with the omission of the Photofoil snoot! The flash was set to Manual, 1/16th power.

Click on image to view 800 pixels wide


By reducing the flash power output in one third stop increments the background gets progressively darker whilst retaining tone. Conversely, by increasing the power output the background tone will become brighter.

In the illustration below I’ve started with the flash set at 1/16th power and progressively increased the output to make the white paper background progressively brighter, all the way to 100%. 

Click on image to view 800 pixels wide

Notice that as the light on the background increases how it reflects and spills onto the flash. This can be controlled by careful positioning of the flash or using Photofoil to flag or control where the light falls in relation to you shot. Chroma Zoning is a controllable technique that can be repeated with consistency. If you keep the distance between the flash & background consistent - use a piece of string tied to the lighting stand to measure the flash to background distance; ensure that the zoom setting is the same each time and you’ll get consistent colours. You may want may want to try this with the other colours in the Rosco Strobist collection and record the results. At a later date I’ll repeat the exercise with studio flash to show the flexibility of this technique.

Here I’ve used # 23 Orange to show the effect of one stop increases and decreases in exposure - not so subtle as 1/3 stop increments!

Click on image to view 800 pixels wide

The remaining frames show the other 7 effects colours, which for consistency have all be shot at 1/16 power. These may be darker or lighter than the actual gel looks. Do remember that the darker the gel the less light it transmits, to get a brighter colour you’ll need to increase your flash output. Conversely, paler colours such as # 33 No Colour Pink will need less light to give a true representation. As I’ve said previously, practice and experimentation are the only way to perfect your techniques.

Good luck and please feedback via the comments below!


1 comment:

  1. This is terrific information that I plan to experiment with next week...thank you!

    ReplyDelete