Article by Edwin Brosens - www.edwin-macrophoto.com
Using flash for macro photography is as important as remembering to fit a lens to your DSLR. Why? Well with flash, colours are better, we can control the shades and the shutter speed of the camera increase.
When I first started with macro photography I soon discovered that flash was a necessity and looking at the market, I noticed there were special ringflashes designed for macro photography. However, I didn't like the flat look of the light and the way the shades fell behind the subject as this made the shot lose depth of field. With this in mind, I switched to an off camera flash which connected to my camera via a cable, These days, I use a wireless flash as I can position it where ever I feel is best.
When we are using a macro lens, the distance between lens and subject is 10 cm or less which means if you use a flash that's mounted to the top of your camera the light would be too harsh and you'd end up with the lens' shadow over the subject.
A basic set-up would look like this:
Distance And Diffuse
If working hand-held, use a flash bracket as it'll allow you to work faster, which when photographing insects, is a necessity. If you're using a tripod you can hold the flash and experiment with different distances and angles.
To start with, position your flash 45 degrees from your subject as this will allow a good level of light to fall on your subject without it overpowering the shot. I also use an Omni Bounce diffuser on my flash to soften the light further.
Set the white balance of your camera to flash or daylight. Having said that, many people shoot in RAW when taking macro photos as they can then tweak the white balance during post production.
Your flash has to be set at the right level so your subject won't end up looking overly lit / bright. The level of your flash will also change depending on what subject you're photographing. For example, when photographing butterflies, if the body features more white than brown, I have to set the flash level one step lower.
With a long exposure of 1/10 sec or more you can use strobe flash (check the manual that came with your flash gun to see if this feature is available). With this, you set the flash ratio and the frequency of the flash so it'll let several bursts of flash off in a short time.
For the photo above, I set the flash to: 10 Hz / 20 Times. As a result, the background as well as the wasp's body is well written.
One of the most interesting aspects of using flash for macro photography is when you're trying to capture insects in-flight. Before moving on to shooting tips, I thought I'd point out the importance of understanding your subject's behavior, how it reacts, where it'll be etc. Do your research before heading out and your job will be a lot easier when you get outside. To shoot insects in-flight, use manual focus and set the drive mode of your camera to continuous.
You need to check what level your camera's ISO is set at before setting the flash level as you'll the higher your ISO, the lower your flash level will need to be.
The USe Of Daylight With Flash
Balance your flash levels with daylight and you'll have a shot that's full of colour and a good level of light. I find the best combination is 30% flash with 70% of daylight. But do take the time to experiment with your flashgun at home so you can learn what angles, distances, strengths etc. work the best.