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Flash lighting maybe a great thing to use in the studio for the extreme macro photograph, but there are also flash issues in extreme macro that need to be dealt with.

Some of these issues can be prevented but in the case of others, it is a matter of trying best to minimise the problem.

Flash Ghosting

Flash issues in extreme macro that need to be dealt with

An ugly phenomenon known as flash ghosting can happen when using flash for extreme macro with ambient light, in which a faint grey shadow appears round the rim of the subject. Flash ghosting can be countered by using the rear curtain flash mode. There are various types of flash ghosting and the phenomenon is not especially well understood or explained on the web, and actually quite difficult to look up on the web because the term 'flash ghosting' doesn't exactly spring to mind. So if you have strange flash shadows, dark flash shadows, dark flash edges and don't know what's going on, maybe you'll land on these pages with your google search.

Subject Movement

Electronic flash units are remarkably inconsistent in their operation

Flashes emit a strong pulse of heat, and at the extreme macro scale this can and will move or disturb your specimen, ie flash movement. In the case of butterfly scales it can move them, rendering flash useless for stacking, and in the case of small flies (especially Doli flies) the fly reacts faster than the second flash (if using TTL).

Flash Inconsistency

Electronic flash units are remarkably inconsistent in their operation, and there is no obvious reason why this should be so. Take 100 frames with a flash and you'll see colour temperature and exposure variations in about 5% of them, if not more. There are ways to lessen flash inconsistency.

Poor PTTL

My experience with PTTL is somewhat limited because I tend to prefer to use a flash on fixed manual settings, but from what I've seen PTTL just doesn't seem to work all that well when your flash is overhead using a diffuser. But setting -2EV on my Pentax Ringflash does seem to produce very accurate PTTL results.

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