Shallow depth of field is considered a mayor problem taking macro images in magnification higher than 1:1, as most of the subject is out of focus. Several techniques developed to increase the depth of field, I'm not defending one against another because I use most of them in a daily basis. The history of this post is how to use successfully a wide aperture (relatively in extreme macro terms) in one single image still preserving the interestingness.
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| Portrait of a male of Lynx spider by Gustavo Mazzarollo, Canon MP-E 65mm macro photo lens @ 3x magnification and f/6.3, the effective aperture is about f/22 | |
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The main shortcoming is finding a suitable subject that has enough of the body geometry in a flat plane in order to allow the shallow DOF to cover enough area for detail perception. The lynx spider is one of these suitable subjects. These photos were taken with Canon MP-E 65mm macro photo lens @ 3x magnification and f/6.3,
the effective aperture is about f/22 , doesn't look like a lot of aperture, but successful extreme macro shooters that made most of the images single framed usually goo to effective apertures of f/50 or more (flash required). There were advantages of taking the shoot at a wider aperture, it allows more natural light to participate in exposure creating a natural light background, it allows a reduced flash time for the needed exposure and reduce the diffraction softening creating more interesting detail in the in focus area. The subject is still exposed by flash, if the flash fails will result in a shadow image were the spider is, the flash is important to preserve detail too, it stops the motion and prevent macro motion blur, flash power is defined as duration of the pulse, the shorter the pulse the more chance of getting a sharp macro and the wider the aperture the shorter the pulse.
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| Lynx spider side view photo by Gustavo Mazzarollo, Canon MP-E 65mm macro photo lens @ 3x magnification and f/6.3, the effective aperture is about f/22 |
In artistical terms there is not problem in placing a small portion of the subject in the point of focus, some people buy expensive fast lenses only to achieve shallow depth of field in human portraits, and conclude that this isn't enough, end by buying a full frame camera, to make the deph of field even shallower, as as far as you have enough detail to be appreciatted and the shape and color of subject present, some brain mechanisms reconstruct the whole image.
I usually do this by doing test shoots and seeing the widest aperture possible that preserve the detail, sometimes I do focus stack of two or a few more images for the effect, but this isn't always possible with a live moving subject. The frontal portrait below was done with several testing aperture in several shoots until figure out the best aperture:
