Macro tip: Shoot parallel to long axis when photographing insects.

Depth of field is a critical parameter in photography.  Whether shooting portraits, landscapes, or extreme close-ups, there are many variables to be considered.  Outside of depth of field, focal length, focus point, aperture, and crop factor, there is another aspect to consider.  It has to do with the subject's position relative to the sensor plane (also called the film plane).

Depth of field decreases as focal length increases and focal distance decreases.  In more technical jargon we say that depth of field is indirectly proportional to focal length (relative millimeter value of lens) and directly proportional to focal distance. (distance between subject and the front of the lens)  The amount in focus in a photo decreases as you get closer to your subject and it also decreases as your focal length increases.  In macro photography, both of these are rendered moot when you start talking about reproduction ratios and depth of field. It turns out that depth of field is exactly the same regardless of these two parameters when the values combine to give any single reproduction ratio (the size of the image on the sensor compared to the size of the actual subject expressed as a ratio).  Aperture values have an enormous impact on depth of field, however.  This is why I choose to shoot with small f/values when photographing insects.  

Even when using very small apertures such as f/32 depth of field is at a premium.  At very large reproduction ratios such as 1:2 and beyond (1:1, 2:1, and so on) the amount in focus is very small.  Its value could be measured in millimeters, not centimeters.  In order to get the closeup of an insect entirely in focus, one has to consider the axis being shot.  Shoot perpendicular to the long axis (inset above) and it is likely that the head and/or tail of the diminutive beast will be blurry.  Take the same photo parallel to the long axis and you may just get everything in focus.  There are a few other techniques that will further improve the process, but this in itself is a significant consideration.

The simple way of saying what was just pointed out is that, when photographing small things like insects, shoot them from the side instead of from the front.  You will end up getting better pictures.  I promise.

Thanks for reading.

Eric Svendsen     www.ericspix.com