Notes on using Flash for Close-up Photography

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For many years, I avoided the use of flash, as the results always appeared unnatural. Recently, however, I have found that a 'dedicated' flash (linked to the camera's own exposure system) can give excellent results, especially when used 'off-camera' with a diffuser. I now frequently use a Nikon SB-600 flashgun, which connects wirelessly to my D300s.

Fig. 1 - Off-camera Flash Setup
© R.Flemming, 2011

In the case of the Nikon system, the wireless flash is triggered by the camera's own pop-up flash (on those camera models that provide this 'Commander' feature). In close-up work, the small amount of light from the on-camera flash can affect the result, and Nikon therefore make a little-known adapter (SG-3IR), shown in Fig. 1, which blocks direct light, while allowing the infra-red content to trigger the remote flash. The diffuser shown on my SB-600 is a simple folding softbox, which slips over the flash head with an elasticated collar

For convenience, I use the 'Custom Settings Menu' on the camera, to pre-set the correct settings for wireless flash in a 'Custom setting bank' since, on the Nikon system, these are difficult to remember in the field! The flashgun itself also needs to be set to receive the wireless signals. Getting good results takes practice and, as modern 'dedicated' flash systems are complex, it is worth spending some time reading the manual. My way with the Nikon system is described below:

I set the camera to Manual Exposure mode and select an aperture appropriate for the subject - typically in the range f/8 to f/22 - together with a shutter speed of, usually, 1/125s. I rely on the SB-600 flashgun to adjust itself for the correct exposure and, of course, it is the flash duration that determines the actual exposure. If the subject is mobile, then a faster shutter speed can be set on the camera and, if the appropriate mode is set in the flash menu, the shutter speed need not be limited to the usual sync maximum (typically 1/250s), when using the SB-600.

A quirk of the Nikon system is that the 'Auto ISO' setting continues to operate in Manual exposure mode, so it is important to turn 'Auto ISO' off, to prevent too high a setting from being applied. I usually use a fixed setting of 400 ISO, to allow use of the smaller apertures needed for close-up work.

It is important to note that, when the camera is set to 'Matrix' metering, the exposure system tries to balance the flash with ambient light whereas, in 'Spot' metering, it does not. This can make a substantial difference to the result and I usually select 'Spot' mode unless I want a 'fill-in' effect in bright sunlight. For convenience, I have assigned the 'Spot' meter mode to the programmable 'Function' button on the front of my D-300s. This allows for a quick change of metering modes, when required.

Although I normally turn off irritating 'beeps' from the camera, I do find that audio confirmation from the flashgun is useful, especially when holding it in an awkward position, where it is difficult to decide whether the output will be sufficient for the selected aperture. I usually try to hold the gun where it will simulate sunlight. It can be very much easier to achieve this, if an 'assistant' (willing partner) is available to hold the flashgun!

I believe that the test of a good flash picture is that it should not be too easy to decide whether flash was used, when examining the final image!


Fig.2 - Fly Agaric (Amanita muscaria)
1/125s @ f/8 with off-camera flash

 

©Mike Flemming, November 2011

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