Off Camera Flash – Part 5

Posted on December 9, 2011


We have covered quite a bit in this series of entries. In this entry, we will cover one more way of softening your flash or making it less obtrusive and then we cover something that is the meat of using a flash.

One more way to make flash less obnoxious is through filter gels. Two of the key and most used filters you will use are CTO and CTB filters. CTO stands for “color to orange” and CTB stands for “color to blue.”  CTO filters warm the light by making the light more orange – more like a traditional bulb light. The CTB filters cool light and are used to convert traditional bulb light more blue and like daylight. You can get a decent set of these specifically for a flash for around $20 (sometimes with a holder) from Lee and Rosco. Where you will see them helpful is in changing the light from the pure white tone that they project, and convert them into a warmer and fuzzier light. You can take the edge off the flashes normal light by adding a 1/2 CTO to 1.5 CTO filter in daylight. When you don’t have a filter this strong, the filters are additive so you can stack them together to get the strength you need. If you have multiple flashes, you can have them at different levels to emphasize different parts of the image (ie-highlights cooler, fill warmer). You can also fake a sunset light at night with CTO filters.

Another way to use filters is to project light on the backgrounds. This is fairly easy to do and will add a bit of color to the image. The key thing to remember here is that you need to keep your main lights from hitting the background, or they will wash out your background with white light – making the filled in light worthless.

Still another way to play with filters is to set your white balance – you do this by gelling your light with the color opposite on the color wheel. Next, use your 18% grey filter pointed to the light, and take an image. Set that “grey” image as your white balance image. It will then shade images in the color opposite the one you gelled. Most people leave the gel on the flash for the images they take – usually neutralizing the close up subject but still toning the rest of the image the other color.

This should give you enough to play with gels a bit. Now, on to a difficult concept with flashes but will make your understanding and creation of images so much better. A flash image is really a double exposure: the first is the flash image and the second is the ambient exposure. Again, the flash is one exposure, and the ambient light is yet another. A flash is usually super fast – it will freeze most action (depending on the type). Because of the speed of a flash, the shutter speed means nothing in exposing your subject. You can play with this by setting your camera to manual, and then play with shooting the same image with just different shutter speeds. When you review your images, they won’t change in exposure – the speed of the flash has set that exposure. If you do this, try to have a full background behind your subject. As you adjust the shutter speed, you will notice that the “fill” on the background (not the subject) changes from one level to another as you move more than one stop or more. This is because the shutter is used to adjust the ambient light hitting the sensor – not the flash. If you have it set to the maximum shutter sync speed, you should notice the background is darker. If you have it set to 1/30 of a second, you will notice that the background is close to properly exposed. If you need to adjust your light on your subject, use the aperture to do this but beware that it will effect your depth of field when you do.

There you have another two techniques to put in your bag for taking pictures. As with the last entry, the information applies to both studio flash and portable flash units. Get out there and play with these a little bit, and see what it will do for your images.