---

There are a lot of flash modes available on today's digital cameras and whilst some of them are useful for extreme macro, some are definitely not.

Some flash modes do the work of thinking about exposure for you, whilst other flash modes are the solution to obscure extreme macro problems rarely encountered by mainstream photographers.

On The Camera

rear curtain flash mode overcomes flash ghosting

With the exception of Pentax, your camera basically controls its flash system (built-in or external) based on the selection you make from the available camera flash modes. Depending on the camera, you can usually select a flash mode button on the camera body or using a flash menu in the camera's main settings. These camera flash modes may also control the way that the camera flash interacts with your main exposure system although that is not always the case. Pentax seems to want to be different for no good reason, and rear sync has to be selected on the flash when using a mounted flash, not on the body.

Rear Curtain Flash Mode

Vital for extreme macro, rear curtain flash mode puts out its flash burst immediately before closing the shutter. For example, on a 2s exposure, you take the shot, the shot exposes and after 1.99 seconds the flash goes off, right at the very end.

The rear curtain flash mode overcomes flash ghosting, a surprisingly common issue with extreme macro photography, even in the studio.

Manual Flash Mode

A flash mode in which the photographer controls the strength of the flash manually, by setting the flash to a range of values.

Manual flash mode is often used in extreme macro because of the limitations of all other modes and the flash mode I use most often for extreme macro.

*TTL Flash Mode

TTL (Through the lens) flash mode was the first rendition of a flash system that lets cameras measure light levels in a scene through its lens. By using the relevant TTL mode for your make, essentially the camera does the thinking for you and fires a preflash, which the camera uses to measure the light, and then vary its power to expose your actual photograph properly. TTL metering seems to be somewhat unreliable with diffusers, and the preflash has been known to scare off small flies before the main flash. I have to dial in -3EV flash compensation on the camera before it comes even close to exposing correctly, and even then it's a little bit touch and go.

HSS Flash Mode

Manual flash is often used in extreme macro because of the limitations of all other modes

One mode - HSS High Speed Sync - allows the use of flash with very short shutter speeds (ie 1/2000 of a sec). In fact the flash fires a series of shots, but so quickly that the human eye cannot see it. But it's a series top to bottom, not one contunuous exposure of light over the entire frame, and this is its limitation.

The fact that it fires a series of shots make its use impractical for insects that shift during the image-taking process. If HSS is the sole source of light then this movement makes for an unsharp image. But, if used as fill, to supplement a shot in which natural light accounts for the overwhelming majority of the light, then it is a great tool to have in the toolbox, as can make all the difference in terms of a little bit of extra pop on a relatively stationary subject. Definitely worth playing with, especially on images shot on a bright sunny day where you want little depth of field. Many flashes are capable of HSS but it's probably something that you'll want to look up how to use in the manual as it tends to involve unusual flash settings.

Front Curtain Flash Mode

Front curtain flash mode puts out its flash burst at the start of the exposure. In other words if you have a 3s exposure, the flash fires at the start of the 3 seconds but the lens remains open to take a full 3s exposure.

Front curtain flash mode has little use in extreme macro except potentially for creative effects.

Auto Flash Mode

Does what it says on the tin - the flash will output light based on its internal reading of the situation. Typically you'll have already set the camera on one of the noddy modes like distant, near etc, and that's how it makes its calculation for flash power output.

---